Add m-esr52 at 52.6.0

83 files changed, 40802 insertions, 0 deletions

diff --git a/devtools/server/actors/actor-registry.js b/devtools/server/actors/actor-registry.js
new file mode 100644
index 000000000..6a083ba6f
--- /dev/null
+++ b/devtools/server/actors/actor-registry.js
@@ -0,0 +1,54 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const protocol = require("devtools/shared/protocol");
+const { method, custom, Arg, Option, RetVal } = protocol;
+
+const { Cu, CC, components } = require("chrome");
+const Services = require("Services");
+const { DebuggerServer } = require("devtools/server/main");
+const { registerActor, unregisterActor } = require("devtools/server/actors/utils/actor-registry-utils");
+const { actorActorSpec, actorRegistrySpec } = require("devtools/shared/specs/actor-registry");
+
+/**
+ * The ActorActor gives you a handle to an actor you've dynamically
+ * registered and allows you to unregister it.
+ */
+const ActorActor = protocol.ActorClassWithSpec(actorActorSpec, {
+  initialize: function (conn, options) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+
+    this.options = options;
+  },
+
+  unregister: function () {
+    unregisterActor(this.options);
+  }
+});
+
+/*
+ * The ActorRegistryActor allows clients to define new actors on the
+ * server. This is particularly useful for addons.
+ */
+const ActorRegistryActor = protocol.ActorClassWithSpec(actorRegistrySpec, {
+  initialize: function (conn) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+  },
+
+  registerActor: function (sourceText, fileName, options) {
+    return registerActor(sourceText, fileName, options).then(() => {
+      let { constructor, type } = options;
+
+      return ActorActor(this.conn, {
+        name: constructor,
+        tab: type.tab,
+        global: type.global
+      });
+    });
+  }
+});
+
+exports.ActorRegistryActor = ActorRegistryActor;
diff --git a/devtools/server/actors/addon.js b/devtools/server/actors/addon.js
new file mode 100644
index 000000000..7f152e984
--- /dev/null
+++ b/devtools/server/actors/addon.js
@@ -0,0 +1,352 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { Ci, Cu } = require("chrome");
+var Services = require("Services");
+var { ActorPool } = require("devtools/server/actors/common");
+var { TabSources } = require("./utils/TabSources");
+var makeDebugger = require("./utils/make-debugger");
+var { ConsoleAPIListener } = require("devtools/server/actors/utils/webconsole-utils");
+var DevToolsUtils = require("devtools/shared/DevToolsUtils");
+var { assert, update } = DevToolsUtils;
+
+loader.lazyRequireGetter(this, "AddonThreadActor", "devtools/server/actors/script", true);
+loader.lazyRequireGetter(this, "unwrapDebuggerObjectGlobal", "devtools/server/actors/script", true);
+loader.lazyRequireGetter(this, "mapURIToAddonID", "devtools/server/actors/utils/map-uri-to-addon-id");
+loader.lazyRequireGetter(this, "WebConsoleActor", "devtools/server/actors/webconsole", true);
+
+loader.lazyImporter(this, "AddonManager", "resource://gre/modules/AddonManager.jsm");
+
+function BrowserAddonActor(aConnection, aAddon) {
+  this.conn = aConnection;
+  this._addon = aAddon;
+  this._contextPool = new ActorPool(this.conn);
+  this.conn.addActorPool(this._contextPool);
+  this.threadActor = null;
+  this._global = null;
+
+  this._shouldAddNewGlobalAsDebuggee = this._shouldAddNewGlobalAsDebuggee.bind(this);
+
+  this.makeDebugger = makeDebugger.bind(null, {
+    findDebuggees: this._findDebuggees.bind(this),
+    shouldAddNewGlobalAsDebuggee: this._shouldAddNewGlobalAsDebuggee
+  });
+
+  AddonManager.addAddonListener(this);
+}
+exports.BrowserAddonActor = BrowserAddonActor;
+
+BrowserAddonActor.prototype = {
+  actorPrefix: "addon",
+
+  get exited() {
+    return !this._addon;
+  },
+
+  get id() {
+    return this._addon.id;
+  },
+
+  get url() {
+    return this._addon.sourceURI ? this._addon.sourceURI.spec : undefined;
+  },
+
+  get attached() {
+    return this.threadActor;
+  },
+
+  get global() {
+    return this._global;
+  },
+
+  get sources() {
+    if (!this._sources) {
+      assert(this.threadActor, "threadActor should exist when creating sources.");
+      this._sources = new TabSources(this.threadActor, this._allowSource);
+    }
+    return this._sources;
+  },
+
+
+  form: function BAA_form() {
+    assert(this.actorID, "addon should have an actorID.");
+    if (!this._consoleActor) {
+      this._consoleActor = new AddonConsoleActor(this._addon, this.conn, this);
+      this._contextPool.addActor(this._consoleActor);
+    }
+
+    return {
+      actor: this.actorID,
+      id: this.id,
+      name: this._addon.name,
+      url: this.url,
+      iconURL: this._addon.iconURL,
+      debuggable: this._addon.isDebuggable,
+      temporarilyInstalled: this._addon.temporarilyInstalled,
+      consoleActor: this._consoleActor.actorID,
+
+      traits: {
+        highlightable: false,
+        networkMonitor: false,
+      },
+    };
+  },
+
+  disconnect: function BAA_disconnect() {
+    this.conn.removeActorPool(this._contextPool);
+    this._contextPool = null;
+    this._consoleActor = null;
+    this._addon = null;
+    this._global = null;
+    AddonManager.removeAddonListener(this);
+  },
+
+  setOptions: function BAA_setOptions(aOptions) {
+    if ("global" in aOptions) {
+      this._global = aOptions.global;
+    }
+  },
+
+  onInstalled: function BAA_updateAddonWrapper(aAddon) {
+    if (aAddon.id != this._addon.id) {
+      return;
+    }
+
+    // Update the AddonManager's addon object on reload/update.
+    this._addon = aAddon;
+  },
+
+  onDisabled: function BAA_onDisabled(aAddon) {
+    if (aAddon != this._addon) {
+      return;
+    }
+
+    this._global = null;
+  },
+
+  onUninstalled: function BAA_onUninstalled(aAddon) {
+    if (aAddon != this._addon) {
+      return;
+    }
+
+    if (this.attached) {
+      this.onDetach();
+
+      // The BrowserAddonActor is not a TabActor and it has to send
+      // "tabDetached" directly to close the devtools toolbox window.
+      this.conn.send({ from: this.actorID, type: "tabDetached" });
+    }
+
+    this.disconnect();
+  },
+
+  onAttach: function BAA_onAttach() {
+    if (this.exited) {
+      return { type: "exited" };
+    }
+
+    if (!this.attached) {
+      this.threadActor = new AddonThreadActor(this.conn, this);
+      this._contextPool.addActor(this.threadActor);
+    }
+
+    return { type: "tabAttached", threadActor: this.threadActor.actorID };
+  },
+
+  onDetach: function BAA_onDetach() {
+    if (!this.attached) {
+      return { error: "wrongState" };
+    }
+
+    this._contextPool.removeActor(this.threadActor);
+
+    this.threadActor = null;
+    this._sources = null;
+
+    return { type: "detached" };
+  },
+
+  onReload: function BAA_onReload() {
+    return this._addon.reload()
+      .then(() => {
+        return {}; // send an empty response
+      });
+  },
+
+  preNest: function () {
+    let e = Services.wm.getEnumerator(null);
+    while (e.hasMoreElements()) {
+      let win = e.getNext();
+      let windowUtils = win.QueryInterface(Ci.nsIInterfaceRequestor)
+                           .getInterface(Ci.nsIDOMWindowUtils);
+      windowUtils.suppressEventHandling(true);
+      windowUtils.suspendTimeouts();
+    }
+  },
+
+  postNest: function () {
+    let e = Services.wm.getEnumerator(null);
+    while (e.hasMoreElements()) {
+      let win = e.getNext();
+      let windowUtils = win.QueryInterface(Ci.nsIInterfaceRequestor)
+                           .getInterface(Ci.nsIDOMWindowUtils);
+      windowUtils.resumeTimeouts();
+      windowUtils.suppressEventHandling(false);
+    }
+  },
+
+  /**
+   * Return true if the given global is associated with this addon and should be
+   * added as a debuggee, false otherwise.
+   */
+  _shouldAddNewGlobalAsDebuggee: function (aGlobal) {
+    const global = unwrapDebuggerObjectGlobal(aGlobal);
+    try {
+      // This will fail for non-Sandbox objects, hence the try-catch block.
+      let metadata = Cu.getSandboxMetadata(global);
+      if (metadata) {
+        return metadata.addonID === this.id;
+      }
+    } catch (e) {}
+
+    if (global instanceof Ci.nsIDOMWindow) {
+      return mapURIToAddonID(global.document.documentURIObject) == this.id;
+    }
+
+    // Check the global for a __URI__ property and then try to map that to an
+    // add-on
+    let uridescriptor = aGlobal.getOwnPropertyDescriptor("__URI__");
+    if (uridescriptor && "value" in uridescriptor && uridescriptor.value) {
+      let uri;
+      try {
+        uri = Services.io.newURI(uridescriptor.value, null, null);
+      }
+      catch (e) {
+        DevToolsUtils.reportException(
+          "BrowserAddonActor.prototype._shouldAddNewGlobalAsDebuggee",
+          new Error("Invalid URI: " + uridescriptor.value)
+        );
+        return false;
+      }
+
+      if (mapURIToAddonID(uri) == this.id) {
+        return true;
+      }
+    }
+
+    return false;
+  },
+
+  /**
+   * Override the eligibility check for scripts and sources to make
+   * sure every script and source with a URL is stored when debugging
+   * add-ons.
+   */
+  _allowSource: function (aSource) {
+    // XPIProvider.jsm evals some code in every add-on's bootstrap.js. Hide it.
+    if (aSource.url === "resource://gre/modules/addons/XPIProvider.jsm") {
+      return false;
+    }
+
+    return true;
+  },
+
+  /**
+   * Yield the current set of globals associated with this addon that should be
+   * added as debuggees.
+   */
+  _findDebuggees: function (dbg) {
+    return dbg.findAllGlobals().filter(this._shouldAddNewGlobalAsDebuggee);
+  }
+};
+
+BrowserAddonActor.prototype.requestTypes = {
+  "attach": BrowserAddonActor.prototype.onAttach,
+  "detach": BrowserAddonActor.prototype.onDetach,
+  "reload": BrowserAddonActor.prototype.onReload
+};
+
+/**
+ * The AddonConsoleActor implements capabilities needed for the add-on web
+ * console feature.
+ *
+ * @constructor
+ * @param object aAddon
+ *        The add-on that this console watches.
+ * @param object aConnection
+ *        The connection to the client, DebuggerServerConnection.
+ * @param object aParentActor
+ *        The parent BrowserAddonActor actor.
+ */
+function AddonConsoleActor(aAddon, aConnection, aParentActor)
+{
+  this.addon = aAddon;
+  WebConsoleActor.call(this, aConnection, aParentActor);
+}
+
+AddonConsoleActor.prototype = Object.create(WebConsoleActor.prototype);
+
+update(AddonConsoleActor.prototype, {
+  constructor: AddonConsoleActor,
+
+  actorPrefix: "addonConsole",
+
+  /**
+   * The add-on that this console watches.
+   */
+  addon: null,
+
+  /**
+   * The main add-on JS global
+   */
+  get window() {
+    return this.parentActor.global;
+  },
+
+  /**
+   * Destroy the current AddonConsoleActor instance.
+   */
+  disconnect: function ACA_disconnect()
+  {
+    WebConsoleActor.prototype.disconnect.call(this);
+    this.addon = null;
+  },
+
+  /**
+   * Handler for the "startListeners" request.
+   *
+   * @param object aRequest
+   *        The JSON request object received from the Web Console client.
+   * @return object
+   *         The response object which holds the startedListeners array.
+   */
+  onStartListeners: function ACA_onStartListeners(aRequest)
+  {
+    let startedListeners = [];
+
+    while (aRequest.listeners.length > 0) {
+      let listener = aRequest.listeners.shift();
+      switch (listener) {
+        case "ConsoleAPI":
+          if (!this.consoleAPIListener) {
+            this.consoleAPIListener =
+              new ConsoleAPIListener(null, this, { addonId: this.addon.id });
+            this.consoleAPIListener.init();
+          }
+          startedListeners.push(listener);
+          break;
+      }
+    }
+    return {
+      startedListeners: startedListeners,
+      nativeConsoleAPI: true,
+      traits: this.traits,
+    };
+  },
+});
+
+AddonConsoleActor.prototype.requestTypes = Object.create(WebConsoleActor.prototype.requestTypes);
+AddonConsoleActor.prototype.requestTypes.startListeners = AddonConsoleActor.prototype.onStartListeners;
diff --git a/devtools/server/actors/addons.js b/devtools/server/actors/addons.js
new file mode 100644
index 000000000..297a3a438
--- /dev/null
+++ b/devtools/server/actors/addons.js
@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {AddonManager} = require("resource://gre/modules/AddonManager.jsm");
+const protocol = require("devtools/shared/protocol");
+const {FileUtils} = require("resource://gre/modules/FileUtils.jsm");
+const {Task} = require("devtools/shared/task");
+const {addonsSpec} = require("devtools/shared/specs/addons");
+
+const AddonsActor = protocol.ActorClassWithSpec(addonsSpec, {
+
+  initialize: function (conn) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+  },
+
+  installTemporaryAddon: Task.async(function* (addonPath) {
+    let addonFile;
+    let addon;
+    try {
+      addonFile = new FileUtils.File(addonPath);
+      addon = yield AddonManager.installTemporaryAddon(addonFile);
+    } catch (error) {
+      throw new Error(`Could not install add-on at '${addonPath}': ${error}`);
+    }
+
+    // TODO: once the add-on actor has been refactored to use
+    // protocol.js, we could return it directly.
+    // return new BrowserAddonActor(this.conn, addon);
+
+    // Return a pseudo add-on object that a calling client can work
+    // with. Provide a flag that the client can use to detect when it
+    // gets upgraded to a real actor object.
+    return { id: addon.id, actor: false };
+
+  }),
+});
+
+exports.AddonsActor = AddonsActor;
diff --git a/devtools/server/actors/animation.js b/devtools/server/actors/animation.js
new file mode 100644
index 000000000..642c4bcaf
--- /dev/null
+++ b/devtools/server/actors/animation.js
@@ -0,0 +1,751 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * Set of actors that expose the Web Animations API to devtools protocol
+ * clients.
+ *
+ * The |Animations| actor is the main entry point. It is used to discover
+ * animation players on given nodes.
+ * There should only be one instance per debugger server.
+ *
+ * The |AnimationPlayer| actor provides attributes and methods to inspect an
+ * animation as well as pause/resume/seek it.
+ *
+ * The Web Animation spec implementation is ongoing in Gecko, and so this set
+ * of actors should evolve when the implementation progresses.
+ *
+ * References:
+ * - WebAnimation spec:
+ *   http://w3c.github.io/web-animations/
+ * - WebAnimation WebIDL files:
+ *   /dom/webidl/Animation*.webidl
+ */
+
+const {Cu} = require("chrome");
+const promise = require("promise");
+const {Task} = require("devtools/shared/task");
+const protocol = require("devtools/shared/protocol");
+const {Actor, ActorClassWithSpec} = protocol;
+const {animationPlayerSpec, animationsSpec} = require("devtools/shared/specs/animation");
+const events = require("sdk/event/core");
+
+// Types of animations.
+const ANIMATION_TYPES = {
+  CSS_ANIMATION: "cssanimation",
+  CSS_TRANSITION: "csstransition",
+  SCRIPT_ANIMATION: "scriptanimation",
+  UNKNOWN: "unknown"
+};
+exports.ANIMATION_TYPES = ANIMATION_TYPES;
+
+/**
+ * The AnimationPlayerActor provides information about a given animation: its
+ * startTime, currentTime, current state, etc.
+ *
+ * Since the state of a player changes as the animation progresses it is often
+ * useful to call getCurrentState at regular intervals to get the current state.
+ *
+ * This actor also allows playing, pausing and seeking the animation.
+ */
+var AnimationPlayerActor = protocol.ActorClassWithSpec(animationPlayerSpec, {
+  /**
+   * @param {AnimationsActor} The main AnimationsActor instance
+   * @param {AnimationPlayer} The player object returned by getAnimationPlayers
+   */
+  initialize: function (animationsActor, player) {
+    Actor.prototype.initialize.call(this, animationsActor.conn);
+
+    this.onAnimationMutation = this.onAnimationMutation.bind(this);
+
+    this.walker = animationsActor.walker;
+    this.player = player;
+
+    // Listen to animation mutations on the node to alert the front when the
+    // current animation changes.
+    // If the node is a pseudo-element, then we listen on its parent with
+    // subtree:true (there's no risk of getting too many notifications in
+    // onAnimationMutation since we filter out events that aren't for the
+    // current animation).
+    this.observer = new this.window.MutationObserver(this.onAnimationMutation);
+    if (this.isPseudoElement) {
+      this.observer.observe(this.node.parentElement,
+                            {animations: true, subtree: true});
+    } else {
+      this.observer.observe(this.node, {animations: true});
+    }
+  },
+
+  destroy: function () {
+    // Only try to disconnect the observer if it's not already dead (i.e. if the
+    // container view hasn't navigated since).
+    if (this.observer && !Cu.isDeadWrapper(this.observer)) {
+      this.observer.disconnect();
+    }
+    this.player = this.observer = this.walker = null;
+
+    Actor.prototype.destroy.call(this);
+  },
+
+  get isPseudoElement() {
+    return !this.player.effect.target.ownerDocument;
+  },
+
+  get node() {
+    if (this._node) {
+      return this._node;
+    }
+
+    let node = this.player.effect.target;
+
+    if (this.isPseudoElement) {
+      // The target is a CSSPseudoElement object which just has a property that
+      // points to its parent element and a string type (::before or ::after).
+      let treeWalker = this.walker.getDocumentWalker(node.parentElement);
+      while (treeWalker.nextNode()) {
+        let currentNode = treeWalker.currentNode;
+        if ((currentNode.nodeName === "_moz_generated_content_before" &&
+             node.type === "::before") ||
+            (currentNode.nodeName === "_moz_generated_content_after" &&
+             node.type === "::after")) {
+          this._node = currentNode;
+        }
+      }
+    } else {
+      // The target is a DOM node.
+      this._node = node;
+    }
+
+    return this._node;
+  },
+
+  get window() {
+    return this.node.ownerDocument.defaultView;
+  },
+
+  /**
+   * Release the actor, when it isn't needed anymore.
+   * Protocol.js uses this release method to call the destroy method.
+   */
+  release: function () {},
+
+  form: function (detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    let data = this.getCurrentState();
+    data.actor = this.actorID;
+
+    // If we know the WalkerActor, and if the animated node is known by it, then
+    // return its corresponding NodeActor ID too.
+    if (this.walker && this.walker.hasNode(this.node)) {
+      data.animationTargetNodeActorID = this.walker.getNode(this.node).actorID;
+    }
+
+    return data;
+  },
+
+  isCssAnimation: function (player = this.player) {
+    return player instanceof this.window.CSSAnimation;
+  },
+
+  isCssTransition: function (player = this.player) {
+    return player instanceof this.window.CSSTransition;
+  },
+
+  isScriptAnimation: function (player = this.player) {
+    return player instanceof this.window.Animation && !(
+      player instanceof this.window.CSSAnimation ||
+      player instanceof this.window.CSSTransition
+    );
+  },
+
+  getType: function () {
+    if (this.isCssAnimation()) {
+      return ANIMATION_TYPES.CSS_ANIMATION;
+    } else if (this.isCssTransition()) {
+      return ANIMATION_TYPES.CSS_TRANSITION;
+    } else if (this.isScriptAnimation()) {
+      return ANIMATION_TYPES.SCRIPT_ANIMATION;
+    }
+
+    return ANIMATION_TYPES.UNKNOWN;
+  },
+
+  /**
+   * Get the name of this animation. This can be either the animation.id
+   * property if it was set, or the keyframe rule name or the transition
+   * property.
+   * @return {String}
+   */
+  getName: function () {
+    if (this.player.id) {
+      return this.player.id;
+    } else if (this.isCssAnimation()) {
+      return this.player.animationName;
+    } else if (this.isCssTransition()) {
+      return this.player.transitionProperty;
+    }
+
+    return "";
+  },
+
+  /**
+   * Get the animation duration from this player, in milliseconds.
+   * @return {Number}
+   */
+  getDuration: function () {
+    return this.player.effect.getComputedTiming().duration;
+  },
+
+  /**
+   * Get the animation delay from this player, in milliseconds.
+   * @return {Number}
+   */
+  getDelay: function () {
+    return this.player.effect.getComputedTiming().delay;
+  },
+
+  /**
+   * Get the animation endDelay from this player, in milliseconds.
+   * @return {Number}
+   */
+  getEndDelay: function () {
+    return this.player.effect.getComputedTiming().endDelay;
+  },
+
+  /**
+   * Get the animation iteration count for this player. That is, how many times
+   * is the animation scheduled to run.
+   * @return {Number} The number of iterations, or null if the animation repeats
+   * infinitely.
+   */
+  getIterationCount: function () {
+    let iterations = this.player.effect.getComputedTiming().iterations;
+    return iterations === "Infinity" ? null : iterations;
+  },
+
+  /**
+   * Get the animation iterationStart from this player, in ratio.
+   * That is offset of starting position of the animation.
+   * @return {Number}
+   */
+  getIterationStart: function () {
+    return this.player.effect.getComputedTiming().iterationStart;
+  },
+
+  /**
+   * Get the animation easing from this player.
+   * @return {String}
+   */
+  getEasing: function () {
+    return this.player.effect.timing.easing;
+  },
+
+  /**
+   * Get the animation fill mode from this player.
+   * @return {String}
+   */
+  getFill: function () {
+    return this.player.effect.getComputedTiming().fill;
+  },
+
+  /**
+   * Get the animation direction from this player.
+   * @return {String}
+   */
+  getDirection: function () {
+    return this.player.effect.getComputedTiming().direction;
+  },
+
+  getPropertiesCompositorStatus: function () {
+    let properties = this.player.effect.getProperties();
+    return properties.map(prop => {
+      return {
+        property: prop.property,
+        runningOnCompositor: prop.runningOnCompositor,
+        warning: prop.warning
+      };
+    });
+  },
+
+  /**
+   * Return the current start of the Animation.
+   * @return {Object}
+   */
+  getState: function () {
+    // Remember the startTime each time getState is called, it may be useful
+    // when animations get paused. As in, when an animation gets paused, its
+    // startTime goes back to null, but the front-end might still be interested
+    // in knowing what the previous startTime was. So everytime it is set,
+    // remember it and send it along with the newState.
+    if (this.player.startTime) {
+      this.previousStartTime = this.player.startTime;
+    }
+
+    // Note that if you add a new property to the state object, make sure you
+    // add the corresponding property in the AnimationPlayerFront' initialState
+    // getter.
+    return {
+      type: this.getType(),
+      // startTime is null whenever the animation is paused or waiting to start.
+      startTime: this.player.startTime,
+      previousStartTime: this.previousStartTime,
+      currentTime: this.player.currentTime,
+      playState: this.player.playState,
+      playbackRate: this.player.playbackRate,
+      name: this.getName(),
+      duration: this.getDuration(),
+      delay: this.getDelay(),
+      endDelay: this.getEndDelay(),
+      iterationCount: this.getIterationCount(),
+      iterationStart: this.getIterationStart(),
+      fill: this.getFill(),
+      easing: this.getEasing(),
+      direction: this.getDirection(),
+      // animation is hitting the fast path or not. Returns false whenever the
+      // animation is paused as it is taken off the compositor then.
+      isRunningOnCompositor:
+        this.getPropertiesCompositorStatus()
+            .some(propState => propState.runningOnCompositor),
+      propertyState: this.getPropertiesCompositorStatus(),
+      // The document timeline's currentTime is being sent along too. This is
+      // not strictly related to the node's animationPlayer, but is useful to
+      // know the current time of the animation with respect to the document's.
+      documentCurrentTime: this.node.ownerDocument.timeline.currentTime
+    };
+  },
+
+  /**
+   * Get the current state of the AnimationPlayer (currentTime, playState, ...).
+   * Note that the initial state is returned as the form of this actor when it
+   * is initialized.
+   * This protocol method only returns a trimed down version of this state in
+   * case some properties haven't changed since last time (since the front can
+   * reconstruct those). If you want the full state, use the getState method.
+   * @return {Object}
+   */
+  getCurrentState: function () {
+    let newState = this.getState();
+
+    // If we've saved a state before, compare and only send what has changed.
+    // It's expected of the front to also save old states to re-construct the
+    // full state when an incomplete one is received.
+    // This is to minimize protocol traffic.
+    let sentState = {};
+    if (this.currentState) {
+      for (let key in newState) {
+        if (typeof this.currentState[key] === "undefined" ||
+            this.currentState[key] !== newState[key]) {
+          sentState[key] = newState[key];
+        }
+      }
+    } else {
+      sentState = newState;
+    }
+    this.currentState = newState;
+
+    return sentState;
+  },
+
+  /**
+   * Executed when the current animation changes, used to emit the new state
+   * the the front.
+   */
+  onAnimationMutation: function (mutations) {
+    let isCurrentAnimation = animation => animation === this.player;
+    let hasCurrentAnimation = animations => animations.some(isCurrentAnimation);
+    let hasChanged = false;
+
+    for (let {removedAnimations, changedAnimations} of mutations) {
+      if (hasCurrentAnimation(removedAnimations)) {
+        // Reset the local copy of the state on removal, since the animation can
+        // be kept on the client and re-added, its state needs to be sent in
+        // full.
+        this.currentState = null;
+      }
+
+      if (hasCurrentAnimation(changedAnimations)) {
+        // Only consider the state has having changed if any of delay, duration,
+        // iterationcount or iterationStart has changed (for now at least).
+        let newState = this.getState();
+        let oldState = this.currentState;
+        hasChanged = newState.delay !== oldState.delay ||
+                     newState.iterationCount !== oldState.iterationCount ||
+                     newState.iterationStart !== oldState.iterationStart ||
+                     newState.duration !== oldState.duration ||
+                     newState.endDelay !== oldState.endDelay;
+        break;
+      }
+    }
+
+    if (hasChanged) {
+      events.emit(this, "changed", this.getCurrentState());
+    }
+  },
+
+  /**
+   * Pause the player.
+   */
+  pause: function () {
+    this.player.pause();
+    return this.player.ready;
+  },
+
+  /**
+   * Play the player.
+   * This method only returns when the animation has left its pending state.
+   */
+  play: function () {
+    this.player.play();
+    return this.player.ready;
+  },
+
+  /**
+   * Simply exposes the player ready promise.
+   *
+   * When an animation is created/paused then played, there's a short time
+   * during which its playState is pending, before being set to running.
+   *
+   * If you either created a new animation using the Web Animations API or
+   * paused/played an existing one, and then want to access the playState, you
+   * might be interested to call this method.
+   * This is especially important for tests.
+   */
+  ready: function () {
+    return this.player.ready;
+  },
+
+  /**
+   * Set the current time of the animation player.
+   */
+  setCurrentTime: function (currentTime) {
+    // The spec is that the progress of animation is changed
+    // if the time of setCurrentTime is during the endDelay.
+    // We should prevent the time
+    // to make the same animation behavior as the original.
+    // Likewise, in case the time is less than 0.
+    const timing = this.player.effect.getComputedTiming();
+    if (timing.delay < 0) {
+      currentTime += timing.delay;
+    }
+    if (currentTime < 0) {
+      currentTime = 0;
+    } else if (currentTime * this.player.playbackRate > timing.endTime) {
+      currentTime = timing.endTime;
+    }
+    this.player.currentTime = currentTime * this.player.playbackRate;
+  },
+
+  /**
+   * Set the playback rate of the animation player.
+   */
+  setPlaybackRate: function (playbackRate) {
+    this.player.playbackRate = playbackRate;
+  },
+
+  /**
+   * Get data about the keyframes of this animation player.
+   * @return {Object} Returns a list of frames, each frame containing the list
+   * animated properties as well as the frame's offset.
+   */
+  getFrames: function () {
+    return this.player.effect.getKeyframes();
+  },
+
+  /**
+   * Get data about the animated properties of this animation player.
+   * @return {Array} Returns a list of animated properties.
+   * Each property contains a list of values and their offsets
+   */
+  getProperties: function () {
+    return this.player.effect.getProperties().map(property => {
+      return {name: property.property, values: property.values};
+    });
+  }
+});
+
+exports.AnimationPlayerActor = AnimationPlayerActor;
+
+/**
+ * The Animations actor lists animation players for a given node.
+ */
+var AnimationsActor = exports.AnimationsActor = protocol.ActorClassWithSpec(animationsSpec, {
+  initialize: function(conn, tabActor) {
+    Actor.prototype.initialize.call(this, conn);
+    this.tabActor = tabActor;
+
+    this.onWillNavigate = this.onWillNavigate.bind(this);
+    this.onNavigate = this.onNavigate.bind(this);
+    this.onAnimationMutation = this.onAnimationMutation.bind(this);
+
+    this.allAnimationsPaused = false;
+    events.on(this.tabActor, "will-navigate", this.onWillNavigate);
+    events.on(this.tabActor, "navigate", this.onNavigate);
+  },
+
+  destroy: function () {
+    Actor.prototype.destroy.call(this);
+    events.off(this.tabActor, "will-navigate", this.onWillNavigate);
+    events.off(this.tabActor, "navigate", this.onNavigate);
+
+    this.stopAnimationPlayerUpdates();
+    this.tabActor = this.observer = this.actors = this.walker = null;
+  },
+
+  /**
+   * Since AnimationsActor doesn't have a protocol.js parent actor that takes
+   * care of its lifetime, implementing disconnect is required to cleanup.
+   */
+  disconnect: function () {
+    this.destroy();
+  },
+
+  /**
+   * Clients can optionally call this with a reference to their WalkerActor.
+   * If they do, then AnimationPlayerActor's forms are going to also include
+   * NodeActor IDs when the corresponding NodeActors do exist.
+   * This, in turns, is helpful for clients to avoid having to go back once more
+   * to the server to get a NodeActor for a particular animation.
+   * @param {WalkerActor} walker
+   */
+  setWalkerActor: function (walker) {
+    this.walker = walker;
+  },
+
+  /**
+   * Retrieve the list of AnimationPlayerActor actors for currently running
+   * animations on a node and its descendants.
+   * Note that calling this method a second time will destroy all previously
+   * retrieved AnimationPlayerActors. Indeed, the lifecycle of these actors
+   * is managed here on the server and tied to getAnimationPlayersForNode
+   * being called.
+   * @param {NodeActor} nodeActor The NodeActor as defined in
+   * /devtools/server/actors/inspector
+   */
+  getAnimationPlayersForNode: function (nodeActor) {
+    let animations = nodeActor.rawNode.getAnimations({subtree: true});
+
+    // Destroy previously stored actors
+    if (this.actors) {
+      this.actors.forEach(actor => actor.destroy());
+    }
+    this.actors = [];
+
+    for (let i = 0; i < animations.length; i++) {
+      let actor = AnimationPlayerActor(this, animations[i]);
+      this.actors.push(actor);
+    }
+
+    // When a front requests the list of players for a node, start listening
+    // for animation mutations on this node to send updates to the front, until
+    // either getAnimationPlayersForNode is called again or
+    // stopAnimationPlayerUpdates is called.
+    this.stopAnimationPlayerUpdates();
+    let win = nodeActor.rawNode.ownerDocument.defaultView;
+    this.observer = new win.MutationObserver(this.onAnimationMutation);
+    this.observer.observe(nodeActor.rawNode, {
+      animations: true,
+      subtree: true
+    });
+
+    return this.actors;
+  },
+
+  onAnimationMutation: function (mutations) {
+    let eventData = [];
+    let readyPromises = [];
+
+    for (let {addedAnimations, removedAnimations} of mutations) {
+      for (let player of removedAnimations) {
+        // Note that animations are reported as removed either when they are
+        // actually removed from the node (e.g. css class removed) or when they
+        // are finished and don't have forwards animation-fill-mode.
+        // In the latter case, we don't send an event, because the corresponding
+        // animation can still be seeked/resumed, so we want the client to keep
+        // its reference to the AnimationPlayerActor.
+        if (player.playState !== "idle") {
+          continue;
+        }
+
+        let index = this.actors.findIndex(a => a.player === player);
+        if (index !== -1) {
+          eventData.push({
+            type: "removed",
+            player: this.actors[index]
+          });
+          this.actors.splice(index, 1);
+        }
+      }
+
+      for (let player of addedAnimations) {
+        // If the added player already exists, it means we previously filtered
+        // it out when it was reported as removed. So filter it out here too.
+        if (this.actors.find(a => a.player === player)) {
+          continue;
+        }
+
+        // If the added player has the same name and target node as a player we
+        // already have, it means it's a transition that's re-starting. So send
+        // a "removed" event for the one we already have.
+        let index = this.actors.findIndex(a => {
+          let isSameType = a.player.constructor === player.constructor;
+          let isSameName = (a.isCssAnimation() &&
+                            a.player.animationName === player.animationName) ||
+                           (a.isCssTransition() &&
+                            a.player.transitionProperty === player.transitionProperty);
+          let isSameNode = a.player.effect.target === player.effect.target;
+
+          return isSameType && isSameNode && isSameName;
+        });
+        if (index !== -1) {
+          eventData.push({
+            type: "removed",
+            player: this.actors[index]
+          });
+          this.actors.splice(index, 1);
+        }
+
+        let actor = AnimationPlayerActor(this, player);
+        this.actors.push(actor);
+        eventData.push({
+          type: "added",
+          player: actor
+        });
+        readyPromises.push(player.ready);
+      }
+    }
+
+    if (eventData.length) {
+      // Let's wait for all added animations to be ready before telling the
+      // front-end.
+      Promise.all(readyPromises).then(() => {
+        events.emit(this, "mutations", eventData);
+      });
+    }
+  },
+
+  /**
+   * After the client has called getAnimationPlayersForNode for a given DOM
+   * node, the actor starts sending animation mutations for this node. If the
+   * client doesn't want this to happen anymore, it should call this method.
+   */
+  stopAnimationPlayerUpdates: function () {
+    if (this.observer && !Cu.isDeadWrapper(this.observer)) {
+      this.observer.disconnect();
+    }
+  },
+
+  /**
+   * Iterates through all nodes below a given rootNode (optionally also in
+   * nested frames) and finds all existing animation players.
+   * @param {DOMNode} rootNode The root node to start iterating at. Animation
+   * players will *not* be reported for this node.
+   * @param {Boolean} traverseFrames Whether we should iterate through nested
+   * frames too.
+   * @return {Array} An array of AnimationPlayer objects.
+   */
+  getAllAnimations: function (rootNode, traverseFrames) {
+    if (!traverseFrames) {
+      return rootNode.getAnimations({subtree: true});
+    }
+
+    let animations = [];
+    for (let {document} of this.tabActor.windows) {
+      animations = [...animations, ...document.getAnimations({subtree: true})];
+    }
+    return animations;
+  },
+
+  onWillNavigate: function ({isTopLevel}) {
+    if (isTopLevel) {
+      this.stopAnimationPlayerUpdates();
+    }
+  },
+
+  onNavigate: function ({isTopLevel}) {
+    if (isTopLevel) {
+      this.allAnimationsPaused = false;
+    }
+  },
+
+  /**
+   * Pause all animations in the current tabActor's frames.
+   */
+  pauseAll: function () {
+    let readyPromises = [];
+    // Until the WebAnimations API provides a way to play/pause via the document
+    // timeline, we have to iterate through the whole DOM to find all players.
+    for (let player of
+         this.getAllAnimations(this.tabActor.window.document, true)) {
+      player.pause();
+      readyPromises.push(player.ready);
+    }
+    this.allAnimationsPaused = true;
+    return promise.all(readyPromises);
+  },
+
+  /**
+   * Play all animations in the current tabActor's frames.
+   * This method only returns when animations have left their pending states.
+   */
+  playAll: function () {
+    let readyPromises = [];
+    // Until the WebAnimations API provides a way to play/pause via the document
+    // timeline, we have to iterate through the whole DOM to find all players.
+    for (let player of
+         this.getAllAnimations(this.tabActor.window.document, true)) {
+      player.play();
+      readyPromises.push(player.ready);
+    }
+    this.allAnimationsPaused = false;
+    return promise.all(readyPromises);
+  },
+
+  toggleAll: function () {
+    if (this.allAnimationsPaused) {
+      return this.playAll();
+    }
+    return this.pauseAll();
+  },
+
+  /**
+   * Toggle (play/pause) several animations at the same time.
+   * @param {Array} players A list of AnimationPlayerActor objects.
+   * @param {Boolean} shouldPause If set to true, the players will be paused,
+   * otherwise they will be played.
+   */
+  toggleSeveral: function (players, shouldPause) {
+    return promise.all(players.map(player => {
+      return shouldPause ? player.pause() : player.play();
+    }));
+  },
+
+  /**
+   * Set the current time of several animations at the same time.
+   * @param {Array} players A list of AnimationPlayerActor.
+   * @param {Number} time The new currentTime.
+   * @param {Boolean} shouldPause Should the players be paused too.
+   */
+  setCurrentTimes: function (players, time, shouldPause) {
+    return promise.all(players.map(player => {
+      let pause = shouldPause ? player.pause() : promise.resolve();
+      return pause.then(() => player.setCurrentTime(time));
+    }));
+  },
+
+  /**
+   * Set the playback rate of several animations at the same time.
+   * @param {Array} players A list of AnimationPlayerActor.
+   * @param {Number} rate The new rate.
+   */
+  setPlaybackRates: function (players, rate) {
+    for (let player of players) {
+      player.setPlaybackRate(rate);
+    }
+  }
+});
diff --git a/devtools/server/actors/breakpoint.js b/devtools/server/actors/breakpoint.js
new file mode 100644
index 000000000..547dcd0f1
--- /dev/null
+++ b/devtools/server/actors/breakpoint.js
@@ -0,0 +1,189 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { ActorClassWithSpec } = require("devtools/shared/protocol");
+const { breakpointSpec } = require("devtools/shared/specs/breakpoint");
+
+/**
+ * Set breakpoints on all the given entry points with the given
+ * BreakpointActor as the handler.
+ *
+ * @param BreakpointActor actor
+ *        The actor handling the breakpoint hits.
+ * @param Array entryPoints
+ *        An array of objects of the form `{ script, offsets }`.
+ */
+function setBreakpointAtEntryPoints(actor, entryPoints) {
+  for (let { script, offsets } of entryPoints) {
+    actor.addScript(script);
+    for (let offset of offsets) {
+      script.setBreakpoint(offset, actor);
+    }
+  }
+}
+
+exports.setBreakpointAtEntryPoints = setBreakpointAtEntryPoints;
+
+/**
+ * BreakpointActors exist for the lifetime of their containing thread and are
+ * responsible for deleting breakpoints, handling breakpoint hits and
+ * associating breakpoints with scripts.
+ */
+let BreakpointActor = ActorClassWithSpec(breakpointSpec, {
+  /**
+   * Create a Breakpoint actor.
+   *
+   * @param ThreadActor threadActor
+   *        The parent thread actor that contains this breakpoint.
+   * @param OriginalLocation originalLocation
+   *        The original location of the breakpoint.
+   */
+  initialize: function (threadActor, originalLocation) {
+    // The set of Debugger.Script instances that this breakpoint has been set
+    // upon.
+    this.scripts = new Set();
+
+    this.threadActor = threadActor;
+    this.originalLocation = originalLocation;
+    this.condition = null;
+    this.isPending = true;
+  },
+
+  disconnect: function () {
+    this.removeScripts();
+  },
+
+  hasScript: function (script) {
+    return this.scripts.has(script);
+  },
+
+  /**
+   * Called when this same breakpoint is added to another Debugger.Script
+   * instance.
+   *
+   * @param script Debugger.Script
+   *        The new source script on which the breakpoint has been set.
+   */
+  addScript: function (script) {
+    this.scripts.add(script);
+    this.isPending = false;
+  },
+
+  /**
+   * Remove the breakpoints from associated scripts and clear the script cache.
+   */
+  removeScripts: function () {
+    for (let script of this.scripts) {
+      script.clearBreakpoint(this);
+    }
+    this.scripts.clear();
+  },
+
+  /**
+   * Check if this breakpoint has a condition that doesn't error and
+   * evaluates to true in frame.
+   *
+   * @param frame Debugger.Frame
+   *        The frame to evaluate the condition in
+   * @returns Object
+   *          - result: boolean|undefined
+   *            True when the conditional breakpoint should trigger a pause,
+   *            false otherwise. If the condition evaluation failed/killed,
+   *            `result` will be `undefined`.
+   *          - message: string
+   *            If the condition throws, this is the thrown message.
+   */
+  checkCondition: function (frame) {
+    let completion = frame.eval(this.condition);
+    if (completion) {
+      if (completion.throw) {
+        // The evaluation failed and threw
+        let message = "Unknown exception";
+        try {
+          if (completion.throw.getOwnPropertyDescriptor) {
+            message = completion.throw.getOwnPropertyDescriptor("message")
+                      .value;
+          } else if (completion.toString) {
+            message = completion.toString();
+          }
+        } catch (ex) {}
+        return {
+          result: true,
+          message: message
+        };
+      } else if (completion.yield) {
+        assert(false, "Shouldn't ever get yield completions from an eval");
+      } else {
+        return { result: completion.return ? true : false };
+      }
+    } else {
+      // The evaluation was killed (possibly by the slow script dialog)
+      return { result: undefined };
+    }
+  },
+
+  /**
+   * A function that the engine calls when a breakpoint has been hit.
+   *
+   * @param frame Debugger.Frame
+   *        The stack frame that contained the breakpoint.
+   */
+  hit: function (frame) {
+    // Don't pause if we are currently stepping (in or over) or the frame is
+    // black-boxed.
+    let generatedLocation = this.threadActor.sources.getFrameLocation(frame);
+    let { originalSourceActor } = this.threadActor.unsafeSynchronize(
+      this.threadActor.sources.getOriginalLocation(generatedLocation));
+    let url = originalSourceActor.url;
+
+    if (this.threadActor.sources.isBlackBoxed(url)
+        || frame.onStep) {
+      return undefined;
+    }
+
+    let reason = {};
+
+    if (this.threadActor._hiddenBreakpoints.has(this.actorID)) {
+      reason.type = "pauseOnDOMEvents";
+    } else if (!this.condition) {
+      reason.type = "breakpoint";
+      // TODO: add the rest of the breakpoints on that line (bug 676602).
+      reason.actors = [ this.actorID ];
+    } else {
+      let { result, message } = this.checkCondition(frame);
+
+      if (result) {
+        if (!message) {
+          reason.type = "breakpoint";
+        } else {
+          reason.type = "breakpointConditionThrown";
+          reason.message = message;
+        }
+        reason.actors = [ this.actorID ];
+      } else {
+        return undefined;
+      }
+    }
+    return this.threadActor._pauseAndRespond(frame, reason);
+  },
+
+  /**
+   * Handle a protocol request to remove this breakpoint.
+   */
+  delete: function () {
+    // Remove from the breakpoint store.
+    if (this.originalLocation) {
+      this.threadActor.breakpointActorMap.deleteActor(this.originalLocation);
+    }
+    this.threadActor.threadLifetimePool.removeActor(this);
+    // Remove the actual breakpoint from the associated scripts.
+    this.removeScripts();
+  }
+});
+
+exports.BreakpointActor = BreakpointActor;
diff --git a/devtools/server/actors/call-watcher.js b/devtools/server/actors/call-watcher.js
new file mode 100644
index 000000000..5729f9508
--- /dev/null
+++ b/devtools/server/actors/call-watcher.js
@@ -0,0 +1,634 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const {Cc, Ci, Cu, Cr} = require("chrome");
+const events = require("sdk/event/core");
+const protocol = require("devtools/shared/protocol");
+const {serializeStack, parseStack} = require("toolkit/loader");
+
+const {on, once, off, emit} = events;
+const {method, Arg, Option, RetVal} = protocol;
+
+const { functionCallSpec, callWatcherSpec } = require("devtools/shared/specs/call-watcher");
+const { CallWatcherFront } = require("devtools/shared/fronts/call-watcher");
+
+/**
+ * This actor contains information about a function call, like the function
+ * type, name, stack, arguments, returned value etc.
+ */
+var FunctionCallActor = protocol.ActorClassWithSpec(functionCallSpec, {
+  /**
+   * Creates the function call actor.
+   *
+   * @param DebuggerServerConnection conn
+   *        The server connection.
+   * @param DOMWindow window
+   *        The content window.
+   * @param string global
+   *        The name of the global object owning this function, like
+   *        "CanvasRenderingContext2D" or "WebGLRenderingContext".
+   * @param object caller
+   *        The object owning the function when it was called.
+   *        For example, in `foo.bar()`, the caller is `foo`.
+   * @param number type
+   *        Either METHOD_FUNCTION, METHOD_GETTER or METHOD_SETTER.
+   * @param string name
+   *        The called function's name.
+   * @param array stack
+   *        The called function's stack, as a list of { name, file, line } objects.
+   * @param number timestamp
+   *        The performance.now() timestamp when the function was called.
+   * @param array args
+   *        The called function's arguments.
+   * @param any result
+   *        The value returned by the function call.
+   * @param boolean holdWeak
+   *        Determines whether or not FunctionCallActor stores a weak reference
+   *        to the underlying objects.
+   */
+  initialize: function (conn, [window, global, caller, type, name, stack, timestamp, args, result], holdWeak) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+
+    this.details = {
+      global: global,
+      type: type,
+      name: name,
+      stack: stack,
+      timestamp: timestamp
+    };
+
+    // Store a weak reference to all objects so we don't
+    // prevent natural GC if `holdWeak` was passed into
+    // setup as truthy.
+    if (holdWeak) {
+      let weakRefs = {
+        window: Cu.getWeakReference(window),
+        caller: Cu.getWeakReference(caller),
+        args: Cu.getWeakReference(args),
+        result: Cu.getWeakReference(result),
+      };
+
+      Object.defineProperties(this.details, {
+        window: { get: () => weakRefs.window.get() },
+        caller: { get: () => weakRefs.caller.get() },
+        args: { get: () => weakRefs.args.get() },
+        result: { get: () => weakRefs.result.get() },
+      });
+    }
+    // Otherwise, hold strong references to the objects.
+    else {
+      this.details.window = window;
+      this.details.caller = caller;
+      this.details.args = args;
+      this.details.result = result;
+    }
+
+    // The caller, args and results are string names for now. It would
+    // certainly be nicer if they were Object actors. Make this smarter, so
+    // that the frontend can inspect each argument, be it object or primitive.
+    // Bug 978960.
+    this.details.previews = {
+      caller: this._generateStringPreview(caller),
+      args: this._generateArgsPreview(args),
+      result: this._generateStringPreview(result)
+    };
+  },
+
+  /**
+   * Customize the marshalling of this actor to provide some generic information
+   * directly on the Front instance.
+   */
+  form: function () {
+    return {
+      actor: this.actorID,
+      type: this.details.type,
+      name: this.details.name,
+      file: this.details.stack[0].file,
+      line: this.details.stack[0].line,
+      timestamp: this.details.timestamp,
+      callerPreview: this.details.previews.caller,
+      argsPreview: this.details.previews.args,
+      resultPreview: this.details.previews.result
+    };
+  },
+
+  /**
+   * Gets more information about this function call, which is not necessarily
+   * available on the Front instance.
+   */
+  getDetails: function () {
+    let { type, name, stack, timestamp } = this.details;
+
+    // Since not all calls on the stack have corresponding owner files (e.g.
+    // callbacks of a requestAnimationFrame etc.), there's no benefit in
+    // returning them, as the user can't jump to the Debugger from them.
+    for (let i = stack.length - 1; ;) {
+      if (stack[i].file) {
+        break;
+      }
+      stack.pop();
+      i--;
+    }
+
+    // XXX: Use grips for objects and serialize them properly, in order
+    // to add the function's caller, arguments and return value. Bug 978957.
+    return {
+      type: type,
+      name: name,
+      stack: stack,
+      timestamp: timestamp
+    };
+  },
+
+  /**
+   * Serializes the arguments so that they can be easily be transferred
+   * as a string, but still be useful when displayed in a potential UI.
+   *
+   * @param array args
+   *        The source arguments.
+   * @return string
+   *         The arguments as a string.
+   */
+  _generateArgsPreview: function (args) {
+    let { global, name, caller } = this.details;
+
+    // Get method signature to determine if there are any enums
+    // used in this method.
+    let methodSignatureEnums;
+
+    let knownGlobal = CallWatcherFront.KNOWN_METHODS[global];
+    if (knownGlobal) {
+      let knownMethod = knownGlobal[name];
+      if (knownMethod) {
+        let isOverloaded = typeof knownMethod.enums === "function";
+        if (isOverloaded) {
+          methodSignatureEnums = methodSignatureEnums(args);
+        } else {
+          methodSignatureEnums = knownMethod.enums;
+        }
+      }
+    }
+
+    let serializeArgs = () => args.map((arg, i) => {
+      // XXX: Bug 978960.
+      if (arg === undefined) {
+        return "undefined";
+      }
+      if (arg === null) {
+        return "null";
+      }
+      if (typeof arg == "function") {
+        return "Function";
+      }
+      if (typeof arg == "object") {
+        return "Object";
+      }
+      // If this argument matches the method's signature
+      // and is an enum, change it to its constant name.
+      if (methodSignatureEnums && methodSignatureEnums.has(i)) {
+        return getBitToEnumValue(global, caller, arg);
+      }
+      return arg + "";
+    });
+
+    return serializeArgs().join(", ");
+  },
+
+  /**
+   * Serializes the data so that it can be easily be transferred
+   * as a string, but still be useful when displayed in a potential UI.
+   *
+   * @param object data
+   *        The source data.
+   * @return string
+   *         The arguments as a string.
+   */
+  _generateStringPreview: function (data) {
+    // XXX: Bug 978960.
+    if (data === undefined) {
+      return "undefined";
+    }
+    if (data === null) {
+      return "null";
+    }
+    if (typeof data == "function") {
+      return "Function";
+    }
+    if (typeof data == "object") {
+      return "Object";
+    }
+    return data + "";
+  }
+});
+
+/**
+ * This actor observes function calls on certain objects or globals.
+ */
+var CallWatcherActor = exports.CallWatcherActor = protocol.ActorClassWithSpec(callWatcherSpec, {
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.tabActor = tabActor;
+    this._onGlobalCreated = this._onGlobalCreated.bind(this);
+    this._onGlobalDestroyed = this._onGlobalDestroyed.bind(this);
+    this._onContentFunctionCall = this._onContentFunctionCall.bind(this);
+    on(this.tabActor, "window-ready", this._onGlobalCreated);
+    on(this.tabActor, "window-destroyed", this._onGlobalDestroyed);
+  },
+  destroy: function (conn) {
+    protocol.Actor.prototype.destroy.call(this, conn);
+    off(this.tabActor, "window-ready", this._onGlobalCreated);
+    off(this.tabActor, "window-destroyed", this._onGlobalDestroyed);
+    this.finalize();
+  },
+
+  /**
+   * Lightweight listener invoked whenever an instrumented function is called
+   * while recording. We're doing this to avoid the event emitter overhead,
+   * since this is expected to be a very hot function.
+   */
+  onCall: null,
+
+  /**
+   * Starts waiting for the current tab actor's document global to be
+   * created, in order to instrument the specified objects and become
+   * aware of everything the content does with them.
+   */
+  setup: function ({ tracedGlobals, tracedFunctions, startRecording, performReload, holdWeak, storeCalls }) {
+    if (this._initialized) {
+      return;
+    }
+    this._initialized = true;
+    this._timestampEpoch = 0;
+
+    this._functionCalls = [];
+    this._tracedGlobals = tracedGlobals || [];
+    this._tracedFunctions = tracedFunctions || [];
+    this._holdWeak = !!holdWeak;
+    this._storeCalls = !!storeCalls;
+
+    if (startRecording) {
+      this.resumeRecording();
+    }
+    if (performReload) {
+      this.tabActor.window.location.reload();
+    }
+  },
+
+  /**
+   * Stops listening for document global changes and puts this actor
+   * to hibernation. This method is called automatically just before the
+   * actor is destroyed.
+   */
+  finalize: function () {
+    if (!this._initialized) {
+      return;
+    }
+    this._initialized = false;
+    this._finalized = true;
+
+    this._tracedGlobals = null;
+    this._tracedFunctions = null;
+  },
+
+  /**
+   * Returns whether the instrumented function calls are currently recorded.
+   */
+  isRecording: function () {
+    return this._recording;
+  },
+
+  /**
+   * Initialize the timestamp epoch used to offset function call timestamps.
+   */
+  initTimestampEpoch: function () {
+    this._timestampEpoch = this.tabActor.window.performance.now();
+  },
+
+  /**
+   * Starts recording function calls.
+   */
+  resumeRecording: function () {
+    this._recording = true;
+  },
+
+  /**
+   * Stops recording function calls.
+   */
+  pauseRecording: function () {
+    this._recording = false;
+    return this._functionCalls;
+  },
+
+  /**
+   * Erases all the recorded function calls.
+   * Calling `resumeRecording` or `pauseRecording` does not erase history.
+   */
+  eraseRecording: function () {
+    this._functionCalls = [];
+  },
+
+  /**
+   * Invoked whenever the current tab actor's document global is created.
+   */
+  _onGlobalCreated: function ({window, id, isTopLevel}) {
+    if (!this._initialized) {
+      return;
+    }
+
+    // TODO: bug 981748, support more than just the top-level documents.
+    if (!isTopLevel) {
+      return;
+    }
+
+    let self = this;
+    this._tracedWindowId = id;
+
+    let unwrappedWindow = XPCNativeWrapper.unwrap(window);
+    let callback = this._onContentFunctionCall;
+
+    for (let global of this._tracedGlobals) {
+      let prototype = unwrappedWindow[global].prototype;
+      let properties = Object.keys(prototype);
+      properties.forEach(name => overrideSymbol(global, prototype, name, callback));
+    }
+
+    for (let name of this._tracedFunctions) {
+      overrideSymbol("window", unwrappedWindow, name, callback);
+    }
+
+    /**
+     * Instruments a method, getter or setter on the specified target object to
+     * invoke a callback whenever it is called.
+     */
+    function overrideSymbol(global, target, name, callback) {
+      let propertyDescriptor = Object.getOwnPropertyDescriptor(target, name);
+
+      if (propertyDescriptor.get || propertyDescriptor.set) {
+        overrideAccessor(global, target, name, propertyDescriptor, callback);
+        return;
+      }
+      if (propertyDescriptor.writable && typeof propertyDescriptor.value == "function") {
+        overrideFunction(global, target, name, propertyDescriptor, callback);
+        return;
+      }
+    }
+
+    /**
+     * Instruments a function on the specified target object.
+     */
+    function overrideFunction(global, target, name, descriptor, callback) {
+      // Invoking .apply on an unxrayed content function doesn't work, because
+      // the arguments array is inaccessible to it. Get Xrays back.
+      let originalFunc = Cu.unwaiveXrays(target[name]);
+
+      Cu.exportFunction(function (...args) {
+        let result;
+        try {
+          result = Cu.waiveXrays(originalFunc.apply(this, args));
+        } catch (e) {
+          throw createContentError(e, unwrappedWindow);
+        }
+
+        if (self._recording) {
+          let type = CallWatcherFront.METHOD_FUNCTION;
+          let stack = getStack(name);
+          let timestamp = self.tabActor.window.performance.now() - self._timestampEpoch;
+          callback(unwrappedWindow, global, this, type, name, stack, timestamp, args, result);
+        }
+        return result;
+      }, target, { defineAs: name });
+
+      Object.defineProperty(target, name, {
+        configurable: descriptor.configurable,
+        enumerable: descriptor.enumerable,
+        writable: true
+      });
+    }
+
+    /**
+     * Instruments a getter or setter on the specified target object.
+     */
+    function overrideAccessor(global, target, name, descriptor, callback) {
+      // Invoking .apply on an unxrayed content function doesn't work, because
+      // the arguments array is inaccessible to it. Get Xrays back.
+      let originalGetter = Cu.unwaiveXrays(target.__lookupGetter__(name));
+      let originalSetter = Cu.unwaiveXrays(target.__lookupSetter__(name));
+
+      Object.defineProperty(target, name, {
+        get: function (...args) {
+          if (!originalGetter) return undefined;
+          let result = Cu.waiveXrays(originalGetter.apply(this, args));
+
+          if (self._recording) {
+            let type = CallWatcherFront.GETTER_FUNCTION;
+            let stack = getStack(name);
+            let timestamp = self.tabActor.window.performance.now() - self._timestampEpoch;
+            callback(unwrappedWindow, global, this, type, name, stack, timestamp, args, result);
+          }
+          return result;
+        },
+        set: function (...args) {
+          if (!originalSetter) return;
+          originalSetter.apply(this, args);
+
+          if (self._recording) {
+            let type = CallWatcherFront.SETTER_FUNCTION;
+            let stack = getStack(name);
+            let timestamp = self.tabActor.window.performance.now() - self._timestampEpoch;
+            callback(unwrappedWindow, global, this, type, name, stack, timestamp, args, undefined);
+          }
+        },
+        configurable: descriptor.configurable,
+        enumerable: descriptor.enumerable
+      });
+    }
+
+    /**
+     * Stores the relevant information about calls on the stack when
+     * a function is called.
+     */
+    function getStack(caller) {
+      try {
+        // Using Components.stack wouldn't be a better idea, since it's
+        // much slower because it attempts to retrieve the C++ stack as well.
+        throw new Error();
+      } catch (e) {
+        var stack = e.stack;
+      }
+
+      // Of course, using a simple regex like /(.*?)@(.*):(\d*):\d*/ would be
+      // much prettier, but this is a very hot function, so let's sqeeze
+      // every drop of performance out of it.
+      let calls = [];
+      let callIndex = 0;
+      let currNewLinePivot = stack.indexOf("\n") + 1;
+      let nextNewLinePivot = stack.indexOf("\n", currNewLinePivot);
+
+      while (nextNewLinePivot > 0) {
+        let nameDelimiterIndex = stack.indexOf("@", currNewLinePivot);
+        let columnDelimiterIndex = stack.lastIndexOf(":", nextNewLinePivot - 1);
+        let lineDelimiterIndex = stack.lastIndexOf(":", columnDelimiterIndex - 1);
+
+        if (!calls[callIndex]) {
+          calls[callIndex] = { name: "", file: "", line: 0 };
+        }
+        if (!calls[callIndex + 1]) {
+          calls[callIndex + 1] = { name: "", file: "", line: 0 };
+        }
+
+        if (callIndex > 0) {
+          let file = stack.substring(nameDelimiterIndex + 1, lineDelimiterIndex);
+          let line = stack.substring(lineDelimiterIndex + 1, columnDelimiterIndex);
+          let name = stack.substring(currNewLinePivot, nameDelimiterIndex);
+          calls[callIndex].name = name;
+          calls[callIndex - 1].file = file;
+          calls[callIndex - 1].line = line;
+        } else {
+          // Since the topmost stack frame is actually our overwritten function,
+          // it will not have the expected name.
+          calls[0].name = caller;
+        }
+
+        currNewLinePivot = nextNewLinePivot + 1;
+        nextNewLinePivot = stack.indexOf("\n", currNewLinePivot);
+        callIndex++;
+      }
+
+      return calls;
+    }
+  },
+
+  /**
+   * Invoked whenever the current tab actor's inner window is destroyed.
+   */
+  _onGlobalDestroyed: function ({window, id, isTopLevel}) {
+    if (this._tracedWindowId == id) {
+      this.pauseRecording();
+      this.eraseRecording();
+      this._timestampEpoch = 0;
+    }
+  },
+
+  /**
+   * Invoked whenever an instrumented function is called.
+   */
+  _onContentFunctionCall: function (...details) {
+    // If the consuming tool has finalized call-watcher, ignore the
+    // still-instrumented calls.
+    if (this._finalized) {
+      return;
+    }
+
+    let functionCall = new FunctionCallActor(this.conn, details, this._holdWeak);
+
+    if (this._storeCalls) {
+      this._functionCalls.push(functionCall);
+    }
+
+    if (this.onCall) {
+      this.onCall(functionCall);
+    } else {
+      emit(this, "call", functionCall);
+    }
+  }
+});
+
+/**
+ * A lookup table for cross-referencing flags or properties with their name
+ * assuming they look LIKE_THIS most of the time.
+ *
+ * For example, when gl.clear(gl.COLOR_BUFFER_BIT) is called, the actual passed
+ * argument's value is 16384, which we want identified as "COLOR_BUFFER_BIT".
+ */
+var gEnumRegex = /^[A-Z][A-Z0-9_]+$/;
+var gEnumsLookupTable = {};
+
+// These values are returned from errors, or empty values,
+// and need to be ignored when checking arguments due to the bitwise math.
+var INVALID_ENUMS = [
+  "INVALID_ENUM", "NO_ERROR", "INVALID_VALUE", "OUT_OF_MEMORY", "NONE"
+];
+
+function getBitToEnumValue(type, object, arg) {
+  let table = gEnumsLookupTable[type];
+
+  // If mapping not yet created, do it on the first run.
+  if (!table) {
+    table = gEnumsLookupTable[type] = {};
+
+    for (let key in object) {
+      if (key.match(gEnumRegex)) {
+        // Maps `16384` to `"COLOR_BUFFER_BIT"`, etc.
+        table[object[key]] = key;
+      }
+    }
+  }
+
+  // If a single bit value, just return it.
+  if (table[arg]) {
+    return table[arg];
+  }
+
+  // Otherwise, attempt to reduce it to the original bit flags:
+  // `16640` -> "COLOR_BUFFER_BIT | DEPTH_BUFFER_BIT"
+  let flags = [];
+  for (let flag in table) {
+    if (INVALID_ENUMS.indexOf(table[flag]) !== -1) {
+      continue;
+    }
+
+    // Cast to integer as all values are stored as strings
+    // in `table`
+    flag = flag | 0;
+    if (flag && (arg & flag) === flag) {
+      flags.push(table[flag]);
+    }
+  }
+
+  // Cache the combined bitmask value
+  return table[arg] = flags.join(" | ") || arg;
+}
+
+/**
+ * Creates a new error from an error that originated from content but was called
+ * from a wrapped overridden method. This is so we can make our own error
+ * that does not look like it originated from the call watcher.
+ *
+ * We use toolkit/loader's parseStack and serializeStack rather than the
+ * parsing done in the local `getStack` function, because it does not expose
+ * column number, would have to change the protocol models `call-stack-items` and `call-details`
+ * which hurts backwards compatibility, and the local `getStack` is an optimized, hot function.
+ */
+function createContentError(e, win) {
+  let { message, name, stack } = e;
+  let parsedStack = parseStack(stack);
+  let { fileName, lineNumber, columnNumber } = parsedStack[parsedStack.length - 1];
+  let error;
+
+  let isDOMException = e instanceof Ci.nsIDOMDOMException;
+  let constructor = isDOMException ? win.DOMException : (win[e.name] || win.Error);
+
+  if (isDOMException) {
+    error = new constructor(message, name);
+    Object.defineProperties(error, {
+      code: { value: e.code },
+      columnNumber: { value: 0 }, // columnNumber is always 0 for DOMExceptions?
+      filename: { value: fileName }, // note the lowercase `filename`
+      lineNumber: { value: lineNumber },
+      result: { value: e.result },
+      stack: { value: serializeStack(parsedStack) }
+    });
+  }
+  else {
+    // Constructing an error here retains all the stack information,
+    // and we can add message, fileName and lineNumber via constructor, though
+    // need to manually add columnNumber.
+    error = new constructor(message, fileName, lineNumber);
+    Object.defineProperty(error, "columnNumber", {
+      value: columnNumber
+    });
+  }
+  return error;
+}
diff --git a/devtools/server/actors/canvas.js b/devtools/server/actors/canvas.js
new file mode 100644
index 000000000..f6e1f57ec
--- /dev/null
+++ b/devtools/server/actors/canvas.js
@@ -0,0 +1,728 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const {Cc, Ci, Cu, Cr} = require("chrome");
+const events = require("sdk/event/core");
+const promise = require("promise");
+const protocol = require("devtools/shared/protocol");
+const {CallWatcherActor} = require("devtools/server/actors/call-watcher");
+const {CallWatcherFront} = require("devtools/shared/fronts/call-watcher");
+const DevToolsUtils = require("devtools/shared/DevToolsUtils");
+const {WebGLPrimitiveCounter} = require("devtools/server/primitive");
+const {
+  frameSnapshotSpec,
+  canvasSpec,
+  CANVAS_CONTEXTS,
+  ANIMATION_GENERATORS,
+  LOOP_GENERATORS,
+  DRAW_CALLS,
+  INTERESTING_CALLS,
+} = require("devtools/shared/specs/canvas");
+const {CanvasFront} = require("devtools/shared/fronts/canvas");
+
+const {on, once, off, emit} = events;
+const {method, custom, Arg, Option, RetVal} = protocol;
+
+/**
+ * This actor represents a recorded animation frame snapshot, along with
+ * all the corresponding canvas' context methods invoked in that frame,
+ * thumbnails for each draw call and a screenshot of the end result.
+ */
+var FrameSnapshotActor = protocol.ActorClassWithSpec(frameSnapshotSpec, {
+  /**
+   * Creates the frame snapshot call actor.
+   *
+   * @param DebuggerServerConnection conn
+   *        The server connection.
+   * @param HTMLCanvasElement canvas
+   *        A reference to the content canvas.
+   * @param array calls
+   *        An array of "function-call" actor instances.
+   * @param object screenshot
+   *        A single "snapshot-image" type instance.
+   */
+  initialize: function (conn, { canvas, calls, screenshot, primitive }) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this._contentCanvas = canvas;
+    this._functionCalls = calls;
+    this._animationFrameEndScreenshot = screenshot;
+    this._primitive = primitive;
+  },
+
+  /**
+   * Gets as much data about this snapshot without computing anything costly.
+   */
+  getOverview: function () {
+    return {
+      calls: this._functionCalls,
+      thumbnails: this._functionCalls.map(e => e._thumbnail).filter(e => !!e),
+      screenshot: this._animationFrameEndScreenshot,
+      primitive: {
+        tris: this._primitive.tris,
+        vertices: this._primitive.vertices,
+        points: this._primitive.points,
+        lines: this._primitive.lines
+      }
+    };
+  },
+
+  /**
+   * Gets a screenshot of the canvas's contents after the specified
+   * function was called.
+   */
+  generateScreenshotFor: function (functionCall) {
+    let caller = functionCall.details.caller;
+    let global = functionCall.details.global;
+
+    let canvas = this._contentCanvas;
+    let calls = this._functionCalls;
+    let index = calls.indexOf(functionCall);
+
+    // To get a screenshot, replay all the steps necessary to render the frame,
+    // by invoking the context calls up to and including the specified one.
+    // This will be done in a custom framebuffer in case of a WebGL context.
+    let replayData = ContextUtils.replayAnimationFrame({
+      contextType: global,
+      canvas: canvas,
+      calls: calls,
+      first: 0,
+      last: index
+    });
+
+    let { replayContext, replayContextScaling, lastDrawCallIndex, doCleanup } = replayData;
+    let [left, top, width, height] = replayData.replayViewport;
+    let screenshot;
+
+    // Depending on the canvas' context, generating a screenshot is done
+    // in different ways.
+    if (global == "WebGLRenderingContext") {
+      screenshot = ContextUtils.getPixelsForWebGL(replayContext, left, top, width, height);
+      screenshot.flipped = true;
+    } else if (global == "CanvasRenderingContext2D") {
+      screenshot = ContextUtils.getPixelsFor2D(replayContext, left, top, width, height);
+      screenshot.flipped = false;
+    }
+
+    // In case of the WebGL context, we also need to reset the framebuffer
+    // binding to the original value, after generating the screenshot.
+    doCleanup();
+
+    screenshot.scaling = replayContextScaling;
+    screenshot.index = lastDrawCallIndex;
+    return screenshot;
+  }
+});
+
+/**
+ * This Canvas Actor handles simple instrumentation of all the methods
+ * of a 2D or WebGL context, to provide information regarding all the calls
+ * made when drawing frame inside an animation loop.
+ */
+var CanvasActor = exports.CanvasActor = protocol.ActorClassWithSpec(canvasSpec, {
+  // Reset for each recording, boolean indicating whether or not
+  // any draw calls were called for a recording.
+  _animationContainsDrawCall: false,
+
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.tabActor = tabActor;
+    this._webGLPrimitiveCounter = new WebGLPrimitiveCounter(tabActor);
+    this._onContentFunctionCall = this._onContentFunctionCall.bind(this);
+  },
+  destroy: function (conn) {
+    protocol.Actor.prototype.destroy.call(this, conn);
+    this._webGLPrimitiveCounter.destroy();
+    this.finalize();
+  },
+
+  /**
+   * Starts listening for function calls.
+   */
+  setup: function ({ reload }) {
+    if (this._initialized) {
+      if (reload) {
+        this.tabActor.window.location.reload();
+      }
+      return;
+    }
+    this._initialized = true;
+
+    this._callWatcher = new CallWatcherActor(this.conn, this.tabActor);
+    this._callWatcher.onCall = this._onContentFunctionCall;
+    this._callWatcher.setup({
+      tracedGlobals: CANVAS_CONTEXTS,
+      tracedFunctions: [...ANIMATION_GENERATORS, ...LOOP_GENERATORS],
+      performReload: reload,
+      storeCalls: true
+    });
+  },
+
+  /**
+   * Stops listening for function calls.
+   */
+  finalize: function () {
+    if (!this._initialized) {
+      return;
+    }
+    this._initialized = false;
+
+    this._callWatcher.finalize();
+    this._callWatcher = null;
+  },
+
+  /**
+   * Returns whether this actor has been set up.
+   */
+  isInitialized: function () {
+    return !!this._initialized;
+  },
+
+  /**
+   * Returns whether or not the CanvasActor is recording an animation.
+   * Used in tests.
+   */
+  isRecording: function () {
+    return !!this._callWatcher.isRecording();
+  },
+
+  /**
+   * Records a snapshot of all the calls made during the next animation frame.
+   * The animation should be implemented via the de-facto requestAnimationFrame
+   * utility, or inside recursive `setTimeout`s. `setInterval` at this time are not supported.
+   */
+  recordAnimationFrame: function () {
+    if (this._callWatcher.isRecording()) {
+      return this._currentAnimationFrameSnapshot.promise;
+    }
+
+    this._recordingContainsDrawCall = false;
+    this._callWatcher.eraseRecording();
+    this._callWatcher.initTimestampEpoch();
+    this._webGLPrimitiveCounter.resetCounts();
+    this._callWatcher.resumeRecording();
+
+    let deferred = this._currentAnimationFrameSnapshot = promise.defer();
+    return deferred.promise;
+  },
+
+  /**
+   * Cease attempts to record an animation frame.
+   */
+  stopRecordingAnimationFrame: function () {
+    if (!this._callWatcher.isRecording()) {
+      return;
+    }
+    this._animationStarted = false;
+    this._callWatcher.pauseRecording();
+    this._callWatcher.eraseRecording();
+    this._currentAnimationFrameSnapshot.resolve(null);
+    this._currentAnimationFrameSnapshot = null;
+  },
+
+  /**
+   * Invoked whenever an instrumented function is called, be it on a
+   * 2d or WebGL context, or an animation generator like requestAnimationFrame.
+   */
+  _onContentFunctionCall: function (functionCall) {
+    let { window, name, args } = functionCall.details;
+
+    // The function call arguments are required to replay animation frames,
+    // in order to generate screenshots. However, simply storing references to
+    // every kind of object is a bad idea, since their properties may change.
+    // Consider transformation matrices for example, which are typically
+    // Float32Arrays whose values can easily change across context calls.
+    // They need to be cloned.
+    inplaceShallowCloneArrays(args, window);
+
+    // Handle animations generated using requestAnimationFrame
+    if (CanvasFront.ANIMATION_GENERATORS.has(name)) {
+      this._handleAnimationFrame(functionCall);
+      return;
+    }
+    // Handle animations generated using setTimeout. While using
+    // those timers is considered extremely poor practice, they're still widely
+    // used on the web, especially for old demos; it's nice to support them as well.
+    if (CanvasFront.LOOP_GENERATORS.has(name)) {
+      this._handleAnimationFrame(functionCall);
+      return;
+    }
+    if (CanvasFront.DRAW_CALLS.has(name) && this._animationStarted) {
+      this._handleDrawCall(functionCall);
+      this._webGLPrimitiveCounter.handleDrawPrimitive(functionCall);
+      return;
+    }
+  },
+
+  /**
+   * Handle animations generated using requestAnimationFrame.
+   */
+  _handleAnimationFrame: function (functionCall) {
+    if (!this._animationStarted) {
+      this._handleAnimationFrameBegin();
+    }
+    // Check to see if draw calls occurred yet, as it could be future frames,
+    // like in the scenario where requestAnimationFrame is called to trigger an animation,
+    // and rAF is at the beginning of the animate loop.
+    else if (this._animationContainsDrawCall) {
+      this._handleAnimationFrameEnd(functionCall);
+    }
+  },
+
+  /**
+   * Called whenever an animation frame rendering begins.
+   */
+  _handleAnimationFrameBegin: function () {
+    this._callWatcher.eraseRecording();
+    this._animationStarted = true;
+  },
+
+  /**
+   * Called whenever an animation frame rendering ends.
+   */
+  _handleAnimationFrameEnd: function () {
+    // Get a hold of all the function calls made during this animation frame.
+    // Since only one snapshot can be recorded at a time, erase all the
+    // previously recorded calls.
+    let functionCalls = this._callWatcher.pauseRecording();
+    this._callWatcher.eraseRecording();
+    this._animationContainsDrawCall = false;
+
+    // Since the animation frame finished, get a hold of the (already retrieved)
+    // canvas pixels to conveniently create a screenshot of the final rendering.
+    let index = this._lastDrawCallIndex;
+    let width = this._lastContentCanvasWidth;
+    let height = this._lastContentCanvasHeight;
+    let flipped = !!this._lastThumbnailFlipped; // undefined -> false
+    let pixels = ContextUtils.getPixelStorage()["8bit"];
+    let primitiveResult = this._webGLPrimitiveCounter.getCounts();
+    let animationFrameEndScreenshot = {
+      index: index,
+      width: width,
+      height: height,
+      scaling: 1,
+      flipped: flipped,
+      pixels: pixels.subarray(0, width * height * 4)
+    };
+
+    // Wrap the function calls and screenshot in a FrameSnapshotActor instance,
+    // which will resolve the promise returned by `recordAnimationFrame`.
+    let frameSnapshot = new FrameSnapshotActor(this.conn, {
+      canvas: this._lastDrawCallCanvas,
+      calls: functionCalls,
+      screenshot: animationFrameEndScreenshot,
+      primitive: {
+        tris: primitiveResult.tris,
+        vertices: primitiveResult.vertices,
+        points: primitiveResult.points,
+        lines: primitiveResult.lines
+      }
+    });
+
+    this._currentAnimationFrameSnapshot.resolve(frameSnapshot);
+    this._currentAnimationFrameSnapshot = null;
+    this._animationStarted = false;
+  },
+
+  /**
+   * Invoked whenever a draw call is detected in the animation frame which is
+   * currently being recorded.
+   */
+  _handleDrawCall: function (functionCall) {
+    let functionCalls = this._callWatcher.pauseRecording();
+    let caller = functionCall.details.caller;
+    let global = functionCall.details.global;
+
+    let contentCanvas = this._lastDrawCallCanvas = caller.canvas;
+    let index = this._lastDrawCallIndex = functionCalls.indexOf(functionCall);
+    let w = this._lastContentCanvasWidth = contentCanvas.width;
+    let h = this._lastContentCanvasHeight = contentCanvas.height;
+
+    // To keep things fast, generate images of small and fixed dimensions.
+    let dimensions = CanvasFront.THUMBNAIL_SIZE;
+    let thumbnail;
+
+    this._animationContainsDrawCall = true;
+
+    // Create a thumbnail on every draw call on the canvas context, to augment
+    // the respective function call actor with this additional data.
+    if (global == "WebGLRenderingContext") {
+      // Check if drawing to a custom framebuffer (when rendering to texture).
+      // Don't create a thumbnail in this particular case.
+      let framebufferBinding = caller.getParameter(caller.FRAMEBUFFER_BINDING);
+      if (framebufferBinding == null) {
+        thumbnail = ContextUtils.getPixelsForWebGL(caller, 0, 0, w, h, dimensions);
+        thumbnail.flipped = this._lastThumbnailFlipped = true;
+        thumbnail.index = index;
+      }
+    } else if (global == "CanvasRenderingContext2D") {
+      thumbnail = ContextUtils.getPixelsFor2D(caller, 0, 0, w, h, dimensions);
+      thumbnail.flipped = this._lastThumbnailFlipped = false;
+      thumbnail.index = index;
+    }
+
+    functionCall._thumbnail = thumbnail;
+    this._callWatcher.resumeRecording();
+  }
+});
+
+/**
+ * A collection of methods for manipulating canvas contexts.
+ */
+var ContextUtils = {
+  /**
+   * WebGL contexts are sensitive to how they're queried. Use this function
+   * to make sure the right context is always retrieved, if available.
+   *
+   * @param HTMLCanvasElement canvas
+   *        The canvas element for which to get a WebGL context.
+   * @param WebGLRenderingContext gl
+   *        The queried WebGL context, or null if unavailable.
+   */
+  getWebGLContext: function (canvas) {
+    return canvas.getContext("webgl") ||
+           canvas.getContext("experimental-webgl");
+  },
+
+  /**
+   * Gets a hold of the rendered pixels in the most efficient way possible for
+   * a canvas with a WebGL context.
+   *
+   * @param WebGLRenderingContext gl
+   *        The WebGL context to get a screenshot from.
+   * @param number srcX [optional]
+   *        The first left pixel that is read from the framebuffer.
+   * @param number srcY [optional]
+   *        The first top pixel that is read from the framebuffer.
+   * @param number srcWidth [optional]
+   *        The number of pixels to read on the X axis.
+   * @param number srcHeight [optional]
+   *        The number of pixels to read on the Y axis.
+   * @param number dstHeight [optional]
+   *        The desired generated screenshot height.
+   * @return object
+   *         An objet containing the screenshot's width, height and pixel data,
+   *         represented as an 8-bit array buffer of r, g, b, a values.
+   */
+  getPixelsForWebGL: function (gl,
+    srcX = 0, srcY = 0,
+    srcWidth = gl.canvas.width,
+    srcHeight = gl.canvas.height,
+    dstHeight = srcHeight)
+  {
+    let contentPixels = ContextUtils.getPixelStorage(srcWidth, srcHeight);
+    let { "8bit": charView, "32bit": intView } = contentPixels;
+    gl.readPixels(srcX, srcY, srcWidth, srcHeight, gl.RGBA, gl.UNSIGNED_BYTE, charView);
+    return this.resizePixels(intView, srcWidth, srcHeight, dstHeight);
+  },
+
+  /**
+   * Gets a hold of the rendered pixels in the most efficient way possible for
+   * a canvas with a 2D context.
+   *
+   * @param CanvasRenderingContext2D ctx
+   *        The 2D context to get a screenshot from.
+   * @param number srcX [optional]
+   *        The first left pixel that is read from the canvas.
+   * @param number srcY [optional]
+   *        The first top pixel that is read from the canvas.
+   * @param number srcWidth [optional]
+   *        The number of pixels to read on the X axis.
+   * @param number srcHeight [optional]
+   *        The number of pixels to read on the Y axis.
+   * @param number dstHeight [optional]
+   *        The desired generated screenshot height.
+   * @return object
+   *         An objet containing the screenshot's width, height and pixel data,
+   *         represented as an 8-bit array buffer of r, g, b, a values.
+   */
+  getPixelsFor2D: function (ctx,
+    srcX = 0, srcY = 0,
+    srcWidth = ctx.canvas.width,
+    srcHeight = ctx.canvas.height,
+    dstHeight = srcHeight)
+  {
+    let { data } = ctx.getImageData(srcX, srcY, srcWidth, srcHeight);
+    let { "32bit": intView } = ContextUtils.usePixelStorage(data.buffer);
+    return this.resizePixels(intView, srcWidth, srcHeight, dstHeight);
+  },
+
+  /**
+   * Resizes the provided pixels to fit inside a rectangle with the specified
+   * height and the same aspect ratio as the source.
+   *
+   * @param Uint32Array srcPixels
+   *        The source pixel data, assuming 32bit/pixel and 4 color components.
+   * @param number srcWidth
+   *        The source pixel data width.
+   * @param number srcHeight
+   *        The source pixel data height.
+   * @param number dstHeight [optional]
+   *        The desired resized pixel data height.
+   * @return object
+   *         An objet containing the resized pixels width, height and data,
+   *         represented as an 8-bit array buffer of r, g, b, a values.
+   */
+  resizePixels: function (srcPixels, srcWidth, srcHeight, dstHeight) {
+    let screenshotRatio = dstHeight / srcHeight;
+    let dstWidth = (srcWidth * screenshotRatio) | 0;
+    let dstPixels = new Uint32Array(dstWidth * dstHeight);
+
+    // If the resized image ends up being completely transparent, returning
+    // an empty array will skip some redundant serialization cycles.
+    let isTransparent = true;
+
+    for (let dstX = 0; dstX < dstWidth; dstX++) {
+      for (let dstY = 0; dstY < dstHeight; dstY++) {
+        let srcX = (dstX / screenshotRatio) | 0;
+        let srcY = (dstY / screenshotRatio) | 0;
+        let cPos = srcX + srcWidth * srcY;
+        let dPos = dstX + dstWidth * dstY;
+        let color = dstPixels[dPos] = srcPixels[cPos];
+        if (color) {
+          isTransparent = false;
+        }
+      }
+    }
+
+    return {
+      width: dstWidth,
+      height: dstHeight,
+      pixels: isTransparent ? [] : new Uint8Array(dstPixels.buffer)
+    };
+  },
+
+  /**
+   * Invokes a series of canvas context calls, to "replay" an animation frame
+   * and generate a screenshot.
+   *
+   * In case of a WebGL context, an offscreen framebuffer is created for
+   * the respective canvas, and the rendering will be performed into it.
+   * This is necessary because some state (like shaders, textures etc.) can't
+   * be shared between two different WebGL contexts.
+   *   - Hopefully, once SharedResources are a thing this won't be necessary:
+   *     http://www.khronos.org/webgl/wiki/SharedResouces
+   *   - Alternatively, we could pursue the idea of using the same context
+   *     for multiple canvases, instead of trying to share resources:
+   *     https://www.khronos.org/webgl/public-mailing-list/archives/1210/msg00058.html
+   *
+   * In case of a 2D context, a new canvas is created, since there's no
+   * intrinsic state that can't be easily duplicated.
+   *
+   * @param number contexType
+   *        The type of context to use. See the CallWatcherFront scope types.
+   * @param HTMLCanvasElement canvas
+   *        The canvas element which is the source of all context calls.
+   * @param array calls
+   *        An array of function call actors.
+   * @param number first
+   *        The first function call to start from.
+   * @param number last
+   *        The last (inclusive) function call to end at.
+   * @return object
+   *         The context on which the specified calls were invoked, the
+   *         last registered draw call's index and a cleanup function, which
+   *         needs to be called whenever any potential followup work is finished.
+   */
+  replayAnimationFrame: function ({ contextType, canvas, calls, first, last }) {
+    let w = canvas.width;
+    let h = canvas.height;
+
+    let replayContext;
+    let replayContextScaling;
+    let customViewport;
+    let customFramebuffer;
+    let lastDrawCallIndex = -1;
+    let doCleanup = () => {};
+
+    // In case of WebGL contexts, rendering will be done offscreen, in a
+    // custom framebuffer, but using the same provided context. This is
+    // necessary because it's very memory-unfriendly to rebuild all the
+    // required GL state (like recompiling shaders, setting global flags, etc.)
+    // in an entirely new canvas. However, special care is needed to not
+    // permanently affect the existing GL state in the process.
+    if (contextType == "WebGLRenderingContext") {
+      // To keep things fast, replay the context calls on a framebuffer
+      // of smaller dimensions than the actual canvas (maximum 256x256 pixels).
+      let scaling = Math.min(CanvasFront.WEBGL_SCREENSHOT_MAX_HEIGHT, h) / h;
+      replayContextScaling = scaling;
+      w = (w * scaling) | 0;
+      h = (h * scaling) | 0;
+
+      // Fetch the same WebGL context and bind a new framebuffer.
+      let gl = replayContext = this.getWebGLContext(canvas);
+      let { newFramebuffer, oldFramebuffer } = this.createBoundFramebuffer(gl, w, h);
+      customFramebuffer = newFramebuffer;
+
+      // Set the viewport to match the new framebuffer's dimensions.
+      let { newViewport, oldViewport } = this.setCustomViewport(gl, w, h);
+      customViewport = newViewport;
+
+      // Revert the framebuffer and viewport to the original values.
+      doCleanup = () => {
+        gl.bindFramebuffer(gl.FRAMEBUFFER, oldFramebuffer);
+        gl.viewport.apply(gl, oldViewport);
+      };
+    }
+    // In case of 2D contexts, draw everything on a separate canvas context.
+    else if (contextType == "CanvasRenderingContext2D") {
+      let contentDocument = canvas.ownerDocument;
+      let replayCanvas = contentDocument.createElement("canvas");
+      replayCanvas.width = w;
+      replayCanvas.height = h;
+      replayContext = replayCanvas.getContext("2d");
+      replayContextScaling = 1;
+      customViewport = [0, 0, w, h];
+    }
+
+    // Replay all the context calls up to and including the specified one.
+    for (let i = first; i <= last; i++) {
+      let { type, name, args } = calls[i].details;
+
+      // Prevent WebGL context calls that try to reset the framebuffer binding
+      // to the default value, since we want to perform the rendering offscreen.
+      if (name == "bindFramebuffer" && args[1] == null) {
+        replayContext.bindFramebuffer(replayContext.FRAMEBUFFER, customFramebuffer);
+        continue;
+      }
+      // Also prevent WebGL context calls that try to change the viewport
+      // while our custom framebuffer is bound.
+      if (name == "viewport") {
+        let framebufferBinding = replayContext.getParameter(replayContext.FRAMEBUFFER_BINDING);
+        if (framebufferBinding == customFramebuffer) {
+          replayContext.viewport.apply(replayContext, customViewport);
+          continue;
+        }
+      }
+      if (type == CallWatcherFront.METHOD_FUNCTION) {
+        replayContext[name].apply(replayContext, args);
+      } else if (type == CallWatcherFront.SETTER_FUNCTION) {
+        replayContext[name] = args;
+      }
+      if (CanvasFront.DRAW_CALLS.has(name)) {
+        lastDrawCallIndex = i;
+      }
+    }
+
+    return {
+      replayContext: replayContext,
+      replayContextScaling: replayContextScaling,
+      replayViewport: customViewport,
+      lastDrawCallIndex: lastDrawCallIndex,
+      doCleanup: doCleanup
+    };
+  },
+
+  /**
+   * Gets an object containing a buffer large enough to hold width * height
+   * pixels, assuming 32bit/pixel and 4 color components.
+   *
+   * This method avoids allocating memory and tries to reuse a common buffer
+   * as much as possible.
+   *
+   * @param number w
+   *        The desired pixel array storage width.
+   * @param number h
+   *        The desired pixel array storage height.
+   * @return object
+   *         The requested pixel array buffer.
+   */
+  getPixelStorage: function (w = 0, h = 0) {
+    let storage = this._currentPixelStorage;
+    if (storage && storage["32bit"].length >= w * h) {
+      return storage;
+    }
+    return this.usePixelStorage(new ArrayBuffer(w * h * 4));
+  },
+
+  /**
+   * Creates and saves the array buffer views used by `getPixelStorage`.
+   *
+   * @param ArrayBuffer buffer
+   *        The raw buffer used as storage for various array buffer views.
+   */
+  usePixelStorage: function (buffer) {
+    let array8bit = new Uint8Array(buffer);
+    let array32bit = new Uint32Array(buffer);
+    return this._currentPixelStorage = {
+      "8bit": array8bit,
+      "32bit": array32bit
+    };
+  },
+
+  /**
+   * Creates a framebuffer of the specified dimensions for a WebGL context,
+   * assuming a RGBA color buffer, a depth buffer and no stencil buffer.
+   *
+   * @param WebGLRenderingContext gl
+   *        The WebGL context to create and bind a framebuffer for.
+   * @param number width
+   *        The desired width of the renderbuffers.
+   * @param number height
+   *        The desired height of the renderbuffers.
+   * @return WebGLFramebuffer
+   *         The generated framebuffer object.
+   */
+  createBoundFramebuffer: function (gl, width, height) {
+    let oldFramebuffer = gl.getParameter(gl.FRAMEBUFFER_BINDING);
+    let oldRenderbufferBinding = gl.getParameter(gl.RENDERBUFFER_BINDING);
+    let oldTextureBinding = gl.getParameter(gl.TEXTURE_BINDING_2D);
+
+    let newFramebuffer = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, newFramebuffer);
+
+    // Use a texture as the color renderbuffer attachment, since consumers of
+    // this function will most likely want to read the rendered pixels back.
+    let colorBuffer = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D, colorBuffer);
+    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
+    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
+    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, width, height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+
+    let depthBuffer = gl.createRenderbuffer();
+    gl.bindRenderbuffer(gl.RENDERBUFFER, depthBuffer);
+    gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, width, height);
+
+    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, colorBuffer, 0);
+    gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, depthBuffer);
+
+    gl.bindTexture(gl.TEXTURE_2D, oldTextureBinding);
+    gl.bindRenderbuffer(gl.RENDERBUFFER, oldRenderbufferBinding);
+
+    return { oldFramebuffer, newFramebuffer };
+  },
+
+  /**
+   * Sets the viewport of the drawing buffer for a WebGL context.
+   * @param WebGLRenderingContext gl
+   * @param number width
+   * @param number height
+   */
+  setCustomViewport: function (gl, width, height) {
+    let oldViewport = XPCNativeWrapper.unwrap(gl.getParameter(gl.VIEWPORT));
+    let newViewport = [0, 0, width, height];
+    gl.viewport.apply(gl, newViewport);
+
+    return { oldViewport, newViewport };
+  }
+};
+
+/**
+ * Goes through all the arguments and creates a one-level shallow copy
+ * of all arrays and array buffers.
+ */
+function inplaceShallowCloneArrays(functionArguments, contentWindow) {
+  let { Object, Array, ArrayBuffer } = contentWindow;
+
+  functionArguments.forEach((arg, index, store) => {
+    if (arg instanceof Array) {
+      store[index] = arg.slice();
+    }
+    if (arg instanceof Object && arg.buffer instanceof ArrayBuffer) {
+      store[index] = new arg.constructor(arg);
+    }
+  });
+}
diff --git a/devtools/server/actors/child-process.js b/devtools/server/actors/child-process.js
new file mode 100644
index 000000000..7b0e2eaf8
--- /dev/null
+++ b/devtools/server/actors/child-process.js
@@ -0,0 +1,146 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cc, Ci, Cu } = require("chrome");
+
+const { ChromeDebuggerActor } = require("devtools/server/actors/script");
+const { WebConsoleActor } = require("devtools/server/actors/webconsole");
+const makeDebugger = require("devtools/server/actors/utils/make-debugger");
+const { ActorPool } = require("devtools/server/main");
+const Services = require("Services");
+const { assert } = require("devtools/shared/DevToolsUtils");
+const { TabSources } = require("./utils/TabSources");
+
+loader.lazyRequireGetter(this, "WorkerActorList", "devtools/server/actors/worker", true);
+
+function ChildProcessActor(aConnection) {
+  this.conn = aConnection;
+  this._contextPool = new ActorPool(this.conn);
+  this.conn.addActorPool(this._contextPool);
+  this.threadActor = null;
+
+  // Use a see-everything debugger
+  this.makeDebugger = makeDebugger.bind(null, {
+    findDebuggees: dbg => dbg.findAllGlobals(),
+    shouldAddNewGlobalAsDebuggee: global => true
+  });
+
+  // Scope into which the webconsole executes:
+  // An empty sandbox with chrome privileges
+  let systemPrincipal = Cc["@mozilla.org/systemprincipal;1"]
+    .createInstance(Ci.nsIPrincipal);
+  let sandbox = Cu.Sandbox(systemPrincipal);
+  this._consoleScope = sandbox;
+
+  this._workerList = null;
+  this._workerActorPool = null;
+  this._onWorkerListChanged = this._onWorkerListChanged.bind(this);
+}
+exports.ChildProcessActor = ChildProcessActor;
+
+ChildProcessActor.prototype = {
+  actorPrefix: "process",
+
+  get isRootActor() {
+    return true;
+  },
+
+  get exited() {
+    return !this._contextPool;
+  },
+
+  get url() {
+    return undefined;
+  },
+
+  get window() {
+    return this._consoleScope;
+  },
+
+  get sources() {
+    if (!this._sources) {
+      assert(this.threadActor, "threadActor should exist when creating sources.");
+      this._sources = new TabSources(this.threadActor);
+    }
+    return this._sources;
+  },
+
+  form: function () {
+    if (!this._consoleActor) {
+      this._consoleActor = new WebConsoleActor(this.conn, this);
+      this._contextPool.addActor(this._consoleActor);
+    }
+
+    if (!this.threadActor) {
+      this.threadActor = new ChromeDebuggerActor(this.conn, this);
+      this._contextPool.addActor(this.threadActor);
+    }
+
+    return {
+      actor: this.actorID,
+      name: "Content process",
+
+      consoleActor: this._consoleActor.actorID,
+      chromeDebugger: this.threadActor.actorID,
+
+      traits: {
+        highlightable: false,
+        networkMonitor: false,
+      },
+    };
+  },
+
+  onListWorkers: function () {
+    if (!this._workerList) {
+      this._workerList = new WorkerActorList(this.conn, {});
+    }
+    return this._workerList.getList().then(actors => {
+      let pool = new ActorPool(this.conn);
+      for (let actor of actors) {
+        pool.addActor(actor);
+      }
+
+      this.conn.removeActorPool(this._workerActorPool);
+      this._workerActorPool = pool;
+      this.conn.addActorPool(this._workerActorPool);
+
+      this._workerList.onListChanged = this._onWorkerListChanged;
+
+      return {
+        "from": this.actorID,
+        "workers": actors.map(actor => actor.form())
+      };
+    });
+  },
+
+  _onWorkerListChanged: function () {
+    this.conn.send({ from: this.actorID, type: "workerListChanged" });
+    this._workerList.onListChanged = null;
+  },
+
+  disconnect: function () {
+    this.conn.removeActorPool(this._contextPool);
+    this._contextPool = null;
+
+    // Tell the live lists we aren't watching any more.
+    if (this._workerList) {
+      this._workerList.onListChanged = null;
+    }
+  },
+
+  preNest: function () {
+    // TODO: freeze windows
+    // window mediator doesn't work in child.
+    // it doesn't throw, but doesn't return any window
+  },
+
+  postNest: function () {
+  },
+};
+
+ChildProcessActor.prototype.requestTypes = {
+  "listWorkers": ChildProcessActor.prototype.onListWorkers,
+};
diff --git a/devtools/server/actors/childtab.js b/devtools/server/actors/childtab.js
new file mode 100644
index 000000000..96d82e281
--- /dev/null
+++ b/devtools/server/actors/childtab.js
@@ -0,0 +1,82 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { Cr } = require("chrome");
+var { TabActor } = require("devtools/server/actors/webbrowser");
+
+/**
+ * Tab actor for documents living in a child process.
+ *
+ * Depends on TabActor, defined in webbrowser.js.
+ */
+
+/**
+ * Creates a tab actor for handling requests to the single tab, like
+ * attaching and detaching. ContentActor respects the actor factories
+ * registered with DebuggerServer.addTabActor.
+ *
+ * @param connection DebuggerServerConnection
+ *        The conection to the client.
+ * @param chromeGlobal
+ *        The content script global holding |content| and |docShell| properties for a tab.
+ * @param prefix
+ *        the prefix used in protocol to create IDs for each actor.
+ *        Used as ID identifying this particular TabActor from the parent process.
+ */
+function ContentActor(connection, chromeGlobal, prefix)
+{
+  this._chromeGlobal = chromeGlobal;
+  this._prefix = prefix;
+  TabActor.call(this, connection, chromeGlobal);
+  this.traits.reconfigure = false;
+  this._sendForm = this._sendForm.bind(this);
+  this._chromeGlobal.addMessageListener("debug:form", this._sendForm);
+
+  Object.defineProperty(this, "docShell", {
+    value: this._chromeGlobal.docShell,
+    configurable: true
+  });
+}
+
+ContentActor.prototype = Object.create(TabActor.prototype);
+
+ContentActor.prototype.constructor = ContentActor;
+
+Object.defineProperty(ContentActor.prototype, "title", {
+  get: function () {
+    return this.window.document.title;
+  },
+  enumerable: true,
+  configurable: true
+});
+
+ContentActor.prototype.exit = function () {
+  if (this._sendForm) {
+    try {
+      this._chromeGlobal.removeMessageListener("debug:form", this._sendForm);
+    } catch (e) {
+      if (e.result != Cr.NS_ERROR_NULL_POINTER) {
+        throw e;
+      }
+      // In some cases, especially when using messageManagers in non-e10s mode, we reach
+      // this point with a dead messageManager which only throws errors but does not
+      // seem to indicate in any other way that it is dead.
+    }
+    this._sendForm = null;
+  }
+
+  TabActor.prototype.exit.call(this);
+
+  this._chromeGlobal = null;
+};
+
+/**
+ * On navigation events, our URL and/or title may change, so we update our
+ * counterpart in the parent process that participates in the tab list.
+ */
+ContentActor.prototype._sendForm = function () {
+  this._chromeGlobal.sendAsyncMessage("debug:form", this.form());
+};
diff --git a/devtools/server/actors/chrome.js b/devtools/server/actors/chrome.js
new file mode 100644
index 000000000..07cd2ad99
--- /dev/null
+++ b/devtools/server/actors/chrome.js
@@ -0,0 +1,185 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Ci } = require("chrome");
+const Services = require("Services");
+const { DebuggerServer } = require("../main");
+const { getChildDocShells, TabActor } = require("./webbrowser");
+const makeDebugger = require("./utils/make-debugger");
+
+/**
+ * Creates a TabActor for debugging all the chrome content in the
+ * current process. Most of the implementation is inherited from TabActor.
+ * ChromeActor is a child of RootActor, it can be instanciated via
+ * RootActor.getProcess request.
+ * ChromeActor exposes all tab actors via its form() request, like TabActor.
+ *
+ * History lecture:
+ * All tab actors used to also be registered as global actors,
+ * so that the root actor was also exposing tab actors for the main process.
+ * Tab actors ended up having RootActor as parent actor,
+ * but more and more features of the tab actors were relying on TabActor.
+ * So we are now exposing a process actor that offers the same API as TabActor
+ * by inheriting its functionality.
+ * Global actors are now only the actors that are meant to be global,
+ * and are no longer related to any specific scope/document.
+ *
+ * @param aConnection DebuggerServerConnection
+ *        The connection to the client.
+ */
+function ChromeActor(aConnection) {
+  TabActor.call(this, aConnection);
+
+  // This creates a Debugger instance for chrome debugging all globals.
+  this.makeDebugger = makeDebugger.bind(null, {
+    findDebuggees: dbg => dbg.findAllGlobals(),
+    shouldAddNewGlobalAsDebuggee: () => true
+  });
+
+  // Ensure catching the creation of any new content docshell
+  this.listenForNewDocShells = true;
+
+  // Defines the default docshell selected for the tab actor
+  let window = Services.wm.getMostRecentWindow(DebuggerServer.chromeWindowType);
+
+  // Default to any available top level window if there is no expected window
+  // (for example when we open firefox with -webide argument)
+  if (!window) {
+    window = Services.wm.getMostRecentWindow(null);
+  }
+  // On xpcshell, there is no window/docshell
+  let docShell = window ? window.QueryInterface(Ci.nsIInterfaceRequestor)
+                                .getInterface(Ci.nsIDocShell)
+                        : null;
+  Object.defineProperty(this, "docShell", {
+    value: docShell,
+    configurable: true
+  });
+}
+exports.ChromeActor = ChromeActor;
+
+ChromeActor.prototype = Object.create(TabActor.prototype);
+
+ChromeActor.prototype.constructor = ChromeActor;
+
+ChromeActor.prototype.isRootActor = true;
+
+/**
+ * Getter for the list of all docshells in this tabActor
+ * @return {Array}
+ */
+Object.defineProperty(ChromeActor.prototype, "docShells", {
+  get: function () {
+    // Iterate over all top-level windows and all their docshells.
+    let docShells = [];
+    let e = Services.ww.getWindowEnumerator();
+    while (e.hasMoreElements()) {
+      let window = e.getNext();
+      let docShell = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                           .getInterface(Ci.nsIWebNavigation)
+                           .QueryInterface(Ci.nsIDocShell);
+      docShells = docShells.concat(getChildDocShells(docShell));
+    }
+
+    return docShells;
+  }
+});
+
+ChromeActor.prototype.observe = function (aSubject, aTopic, aData) {
+  TabActor.prototype.observe.call(this, aSubject, aTopic, aData);
+  if (!this.attached) {
+    return;
+  }
+  if (aTopic == "chrome-webnavigation-create") {
+    aSubject.QueryInterface(Ci.nsIDocShell);
+    this._onDocShellCreated(aSubject);
+  } else if (aTopic == "chrome-webnavigation-destroy") {
+    this._onDocShellDestroy(aSubject);
+  }
+};
+
+ChromeActor.prototype._attach = function () {
+  if (this.attached) {
+    return false;
+  }
+
+  TabActor.prototype._attach.call(this);
+
+  // Listen for any new/destroyed chrome docshell
+  Services.obs.addObserver(this, "chrome-webnavigation-create", false);
+  Services.obs.addObserver(this, "chrome-webnavigation-destroy", false);
+
+  // Iterate over all top-level windows.
+  let docShells = [];
+  let e = Services.ww.getWindowEnumerator();
+  while (e.hasMoreElements()) {
+    let window = e.getNext();
+    let docShell = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIWebNavigation)
+                         .QueryInterface(Ci.nsIDocShell);
+    if (docShell == this.docShell) {
+      continue;
+    }
+    this._progressListener.watch(docShell);
+  }
+};
+
+ChromeActor.prototype._detach = function () {
+  if (!this.attached) {
+    return false;
+  }
+
+  Services.obs.removeObserver(this, "chrome-webnavigation-create");
+  Services.obs.removeObserver(this, "chrome-webnavigation-destroy");
+
+  // Iterate over all top-level windows.
+  let docShells = [];
+  let e = Services.ww.getWindowEnumerator();
+  while (e.hasMoreElements()) {
+    let window = e.getNext();
+    let docShell = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIWebNavigation)
+                         .QueryInterface(Ci.nsIDocShell);
+    if (docShell == this.docShell) {
+      continue;
+    }
+    this._progressListener.unwatch(docShell);
+  }
+
+  TabActor.prototype._detach.call(this);
+};
+
+/* ThreadActor hooks. */
+
+/**
+ * Prepare to enter a nested event loop by disabling debuggee events.
+ */
+ChromeActor.prototype.preNest = function () {
+  // Disable events in all open windows.
+  let e = Services.wm.getEnumerator(null);
+  while (e.hasMoreElements()) {
+    let win = e.getNext();
+    let windowUtils = win.QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIDOMWindowUtils);
+    windowUtils.suppressEventHandling(true);
+    windowUtils.suspendTimeouts();
+  }
+};
+
+/**
+ * Prepare to exit a nested event loop by enabling debuggee events.
+ */
+ChromeActor.prototype.postNest = function (aNestData) {
+  // Enable events in all open windows.
+  let e = Services.wm.getEnumerator(null);
+  while (e.hasMoreElements()) {
+    let win = e.getNext();
+    let windowUtils = win.QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIDOMWindowUtils);
+    windowUtils.resumeTimeouts();
+    windowUtils.suppressEventHandling(false);
+  }
+};
diff --git a/devtools/server/actors/common.js b/devtools/server/actors/common.js
new file mode 100644
index 000000000..0177c6749
--- /dev/null
+++ b/devtools/server/actors/common.js
@@ -0,0 +1,521 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const promise = require("promise");
+const { method } = require("devtools/shared/protocol");
+
+/**
+ * Creates "registered" actors factory meant for creating another kind of
+ * factories, ObservedActorFactory, during the call to listTabs.
+ * These factories live in DebuggerServer.{tab|global}ActorFactories.
+ *
+ * These actors only exposes:
+ * - `name` string attribute used to match actors by constructor name
+ *   in DebuggerServer.remove{Global,Tab}Actor.
+ * - `createObservedActorFactory` function to create "observed" actors factory
+ *
+ * @param options object, function
+ *        Either an object or a function.
+ *        If given an object:
+ *
+ *        If given a function (deprecated):
+ *          Constructor function of an actor.
+ *          The constructor function for this actor type.
+ *          This expects to be called as a constructor (i.e. with 'new'),
+ *          and passed two arguments: the DebuggerServerConnection, and
+ *          the BrowserTabActor with which it will be associated.
+ *          Only used for deprecated eagerly loaded actors.
+ *
+ */
+function RegisteredActorFactory(options, prefix) {
+  // By default the actor name will also be used for the actorID prefix.
+  this._prefix = prefix;
+  if (typeof (options) != "function") {
+    // actors definition registered by actorRegistryActor
+    if (options.constructorFun) {
+      this._getConstructor = () => options.constructorFun;
+    } else {
+      // Lazy actor definition, where options contains all the information
+      // required to load the actor lazily.
+      this._getConstructor = function () {
+        // Load the module
+        let mod;
+        try {
+          mod = require(options.id);
+        } catch (e) {
+          throw new Error("Unable to load actor module '" + options.id + "'.\n" +
+                          e.message + "\n" + e.stack + "\n");
+        }
+        // Fetch the actor constructor
+        let c = mod[options.constructorName];
+        if (!c) {
+          throw new Error("Unable to find actor constructor named '" +
+                          options.constructorName + "'. (Is it exported?)");
+        }
+        return c;
+      };
+    }
+    // Exposes `name` attribute in order to allow removeXXXActor to match
+    // the actor by its actor constructor name.
+    this.name = options.constructorName;
+  } else {
+    // Old actor case, where options is a function that is the actor constructor.
+    this._getConstructor = () => options;
+    // Exposes `name` attribute in order to allow removeXXXActor to match
+    // the actor by its actor constructor name.
+    this.name = options.name;
+
+    // For old actors, we allow the use of a different prefix for actorID
+    // than for listTabs actor names, by fetching a prefix on the actor prototype.
+    // (Used by ChromeDebuggerActor)
+    if (options.prototype && options.prototype.actorPrefix) {
+      this._prefix = options.prototype.actorPrefix;
+    }
+  }
+}
+RegisteredActorFactory.prototype.createObservedActorFactory = function (conn, parentActor) {
+  return new ObservedActorFactory(this._getConstructor, this._prefix, conn, parentActor);
+};
+exports.RegisteredActorFactory = RegisteredActorFactory;
+
+/**
+ * Creates "observed" actors factory meant for creating real actor instances.
+ * These factories lives in actor pools and fake various actor attributes.
+ * They will be replaced in actor pools by final actor instances during
+ * the first request for the same actorID from DebuggerServer._getOrCreateActor.
+ *
+ * ObservedActorFactory fakes the following actors attributes:
+ *   actorPrefix (string) Used by ActorPool.addActor to compute the actor id
+ *   actorID (string) Set by ActorPool.addActor just after being instantiated
+ *   registeredPool (object) Set by ActorPool.addActor just after being
+ *                           instantiated
+ * And exposes the following method:
+ *   createActor (function) Instantiate an actor that is going to replace
+ *                          this factory in the actor pool.
+ */
+function ObservedActorFactory(getConstructor, prefix, conn, parentActor) {
+  this._getConstructor = getConstructor;
+  this._conn = conn;
+  this._parentActor = parentActor;
+
+  this.actorPrefix = prefix;
+
+  this.actorID = null;
+  this.registeredPool = null;
+}
+ObservedActorFactory.prototype.createActor = function () {
+  // Fetch the actor constructor
+  let c = this._getConstructor();
+  // Instantiate a new actor instance
+  let instance = new c(this._conn, this._parentActor);
+  instance.conn = this._conn;
+  instance.parentID = this._parentActor.actorID;
+  // We want the newly-constructed actor to completely replace the factory
+  // actor. Reusing the existing actor ID will make sure ActorPool.addActor
+  // does the right thing.
+  instance.actorID = this.actorID;
+  this.registeredPool.addActor(instance);
+  return instance;
+};
+exports.ObservedActorFactory = ObservedActorFactory;
+
+
+/**
+ * Methods shared between RootActor and BrowserTabActor.
+ */
+
+/**
+ * Populate |this._extraActors| as specified by |aFactories|, reusing whatever
+ * actors are already there. Add all actors in the final extra actors table to
+ * |aPool|.
+ *
+ * The root actor and the tab actor use this to instantiate actors that other
+ * parts of the browser have specified with DebuggerServer.addTabActor and
+ * DebuggerServer.addGlobalActor.
+ *
+ * @param aFactories
+ *     An object whose own property names are the names of properties to add to
+ *     some reply packet (say, a tab actor grip or the "listTabs" response
+ *     form), and whose own property values are actor constructor functions, as
+ *     documented for addTabActor and addGlobalActor.
+ *
+ * @param this
+ *     The BrowserRootActor or BrowserTabActor with which the new actors will
+ *     be associated. It should support whatever API the |aFactories|
+ *     constructor functions might be interested in, as it is passed to them.
+ *     For the sake of CommonCreateExtraActors itself, it should have at least
+ *     the following properties:
+ *
+ *     - _extraActors
+ *        An object whose own property names are factory table (and packet)
+ *        property names, and whose values are no-argument actor constructors,
+ *        of the sort that one can add to an ActorPool.
+ *
+ *     - conn
+ *        The DebuggerServerConnection in which the new actors will participate.
+ *
+ *     - actorID
+ *        The actor's name, for use as the new actors' parentID.
+ */
+exports.createExtraActors = function createExtraActors(aFactories, aPool) {
+  // Walk over global actors added by extensions.
+  for (let name in aFactories) {
+    let actor = this._extraActors[name];
+    if (!actor) {
+      // Register another factory, but this time specific to this connection.
+      // It creates a fake actor that looks like an regular actor in the pool,
+      // but without actually instantiating the actor.
+      // It will only be instantiated on the first request made to the actor.
+      actor = aFactories[name].createObservedActorFactory(this.conn, this);
+      this._extraActors[name] = actor;
+    }
+
+    // If the actor already exists in the pool, it may have been instantiated,
+    // so make sure not to overwrite it by a non-instantiated version.
+    if (!aPool.has(actor.actorID)) {
+      aPool.addActor(actor);
+    }
+  }
+};
+
+/**
+ * Append the extra actors in |this._extraActors|, constructed by a prior call
+ * to CommonCreateExtraActors, to |aObject|.
+ *
+ * @param aObject
+ *     The object to which the extra actors should be added, under the
+ *     property names given in the |aFactories| table passed to
+ *     CommonCreateExtraActors.
+ *
+ * @param this
+ *     The BrowserRootActor or BrowserTabActor whose |_extraActors| table we
+ *     should use; see above.
+ */
+exports.appendExtraActors = function appendExtraActors(aObject) {
+  for (let name in this._extraActors) {
+    let actor = this._extraActors[name];
+    aObject[name] = actor.actorID;
+  }
+};
+
+/**
+ * Construct an ActorPool.
+ *
+ * ActorPools are actorID -> actor mapping and storage.  These are
+ * used to accumulate and quickly dispose of groups of actors that
+ * share a lifetime.
+ */
+function ActorPool(aConnection)
+{
+  this.conn = aConnection;
+  this._actors = {};
+}
+
+ActorPool.prototype = {
+  /**
+   * Destroy the pool. This will remove all actors from the pool.
+   */
+  destroy: function AP_destroy() {
+    for (let id in this._actors) {
+      this.removeActor(this._actors[id]);
+    }
+  },
+
+  /**
+   * Add an actor to the pool. If the actor doesn't have an ID, allocate one
+   * from the connection.
+   *
+   * @param Object aActor
+   *        The actor to be added to the pool.
+   */
+  addActor: function AP_addActor(aActor) {
+    aActor.conn = this.conn;
+    if (!aActor.actorID) {
+      let prefix = aActor.actorPrefix;
+      if (!prefix && typeof aActor == "function") {
+        // typeName is a convention used with protocol.js-based actors
+        prefix = aActor.prototype.actorPrefix || aActor.prototype.typeName;
+      }
+      aActor.actorID = this.conn.allocID(prefix || undefined);
+    }
+
+    // If the actor is already in a pool, remove it without destroying it.
+    if (aActor.registeredPool) {
+      delete aActor.registeredPool._actors[aActor.actorID];
+    }
+    aActor.registeredPool = this;
+
+    this._actors[aActor.actorID] = aActor;
+  },
+
+  /**
+   * Remove an actor from the pool. If the actor has a disconnect method, call
+   * it.
+   */
+  removeActor: function AP_remove(aActor) {
+    delete this._actors[aActor.actorID];
+    if (aActor.disconnect) {
+      aActor.disconnect();
+    }
+  },
+
+  get: function AP_get(aActorID) {
+    return this._actors[aActorID] || undefined;
+  },
+
+  has: function AP_has(aActorID) {
+    return aActorID in this._actors;
+  },
+
+  /**
+   * Returns true if the pool is empty.
+   */
+  isEmpty: function AP_isEmpty() {
+    return Object.keys(this._actors).length == 0;
+  },
+
+  /**
+   * Match the api expected by the protocol library.
+   */
+  unmanage: function (aActor) {
+    return this.removeActor(aActor);
+  },
+
+  forEach: function (callback) {
+    for (let name in this._actors) {
+      callback(this._actors[name]);
+    }
+  },
+};
+
+exports.ActorPool = ActorPool;
+
+/**
+ * An OriginalLocation represents a location in an original source.
+ *
+ * @param SourceActor actor
+ *        A SourceActor representing an original source.
+ * @param Number line
+ *        A line within the given source.
+ * @param Number column
+ *        A column within the given line.
+ * @param String name
+ *        The name of the symbol corresponding to this OriginalLocation.
+ */
+function OriginalLocation(actor, line, column, name) {
+  this._connection = actor ? actor.conn : null;
+  this._actorID = actor ? actor.actorID : undefined;
+  this._line = line;
+  this._column = column;
+  this._name = name;
+}
+
+OriginalLocation.fromGeneratedLocation = function (generatedLocation) {
+  return new OriginalLocation(
+    generatedLocation.generatedSourceActor,
+    generatedLocation.generatedLine,
+    generatedLocation.generatedColumn
+  );
+};
+
+OriginalLocation.prototype = {
+  get originalSourceActor() {
+    return this._connection ? this._connection.getActor(this._actorID) : null;
+  },
+
+  get originalUrl() {
+    let actor = this.originalSourceActor;
+    let source = actor.source;
+    return source ? source.url : actor._originalUrl;
+  },
+
+  get originalLine() {
+    return this._line;
+  },
+
+  get originalColumn() {
+    return this._column;
+  },
+
+  get originalName() {
+    return this._name;
+  },
+
+  get generatedSourceActor() {
+    throw new Error("Shouldn't  access generatedSourceActor from an OriginalLocation");
+  },
+
+  get generatedLine() {
+    throw new Error("Shouldn't access generatedLine from an OriginalLocation");
+  },
+
+  get generatedColumn() {
+    throw new Error("Shouldn't access generatedColumn from an Originallocation");
+  },
+
+  equals: function (other) {
+    return this.originalSourceActor.url == other.originalSourceActor.url &&
+           this.originalLine === other.originalLine &&
+           (this.originalColumn === undefined ||
+            other.originalColumn === undefined ||
+            this.originalColumn === other.originalColumn);
+  },
+
+  toJSON: function () {
+    return {
+      source: this.originalSourceActor.form(),
+      line: this.originalLine,
+      column: this.originalColumn
+    };
+  }
+};
+
+exports.OriginalLocation = OriginalLocation;
+
+/**
+ * A GeneratedLocation represents a location in a generated source.
+ *
+ * @param SourceActor actor
+ *        A SourceActor representing a generated source.
+ * @param Number line
+ *        A line within the given source.
+ * @param Number column
+ *        A column within the given line.
+ */
+function GeneratedLocation(actor, line, column, lastColumn) {
+  this._connection = actor ? actor.conn : null;
+  this._actorID = actor ? actor.actorID : undefined;
+  this._line = line;
+  this._column = column;
+  this._lastColumn = (lastColumn !== undefined) ? lastColumn : column + 1;
+}
+
+GeneratedLocation.fromOriginalLocation = function (originalLocation) {
+  return new GeneratedLocation(
+    originalLocation.originalSourceActor,
+    originalLocation.originalLine,
+    originalLocation.originalColumn
+  );
+};
+
+GeneratedLocation.prototype = {
+  get originalSourceActor() {
+    throw new Error();
+  },
+
+  get originalUrl() {
+    throw new Error("Shouldn't access originalUrl from a GeneratedLocation");
+  },
+
+  get originalLine() {
+    throw new Error("Shouldn't access originalLine from a GeneratedLocation");
+  },
+
+  get originalColumn() {
+    throw new Error("Shouldn't access originalColumn from a GeneratedLocation");
+  },
+
+  get originalName() {
+    throw new Error("Shouldn't access originalName from a GeneratedLocation");
+  },
+
+  get generatedSourceActor() {
+    return this._connection ? this._connection.getActor(this._actorID) : null;
+  },
+
+  get generatedLine() {
+    return this._line;
+  },
+
+  get generatedColumn() {
+    return this._column;
+  },
+
+  get generatedLastColumn() {
+    return this._lastColumn;
+  },
+
+  equals: function (other) {
+    return this.generatedSourceActor.url == other.generatedSourceActor.url &&
+           this.generatedLine === other.generatedLine &&
+           (this.generatedColumn === undefined ||
+            other.generatedColumn === undefined ||
+            this.generatedColumn === other.generatedColumn);
+  },
+
+  toJSON: function () {
+    return {
+      source: this.generatedSourceActor.form(),
+      line: this.generatedLine,
+      column: this.generatedColumn,
+      lastColumn: this.generatedLastColumn
+    };
+  }
+};
+
+exports.GeneratedLocation = GeneratedLocation;
+
+/**
+ * A method decorator that ensures the actor is in the expected state before
+ * proceeding. If the actor is not in the expected state, the decorated method
+ * returns a rejected promise.
+ *
+ * The actor's state must be at this.state property.
+ *
+ * @param String expectedState
+ *        The expected state.
+ * @param String activity
+ *        Additional info about what's going on.
+ * @param Function method
+ *        The actor method to proceed with when the actor is in the expected
+ *        state.
+ *
+ * @returns Function
+ *          The decorated method.
+ */
+function expectState(expectedState, method, activity) {
+  return function (...args) {
+    if (this.state !== expectedState) {
+      const msg = `Wrong state while ${activity}:` +
+                  `Expected '${expectedState}', ` +
+                  `but current state is '${this.state}'.`;
+      return promise.reject(new Error(msg));
+    }
+
+    return method.apply(this, args);
+  };
+}
+
+exports.expectState = expectState;
+
+/**
+ * Proxies a call from an actor to an underlying module, stored
+ * as `bridge` on the actor. This allows a module to be defined in one
+ * place, usable by other modules/actors on the server, but a separate
+ * module defining the actor/RDP definition.
+ *
+ * @see Framerate implementation: devtools/server/performance/framerate.js
+ * @see Framerate actor definition: devtools/server/actors/framerate.js
+ */
+function actorBridge(methodName, definition = {}) {
+  return method(function () {
+    return this.bridge[methodName].apply(this.bridge, arguments);
+  }, definition);
+}
+exports.actorBridge = actorBridge;
+
+/**
+ * Like `actorBridge`, but without a spec definition, for when the actor is
+ * created with `ActorClassWithSpec` rather than vanilla `ActorClass`.
+ */
+function actorBridgeWithSpec (methodName) {
+  return method(function () {
+    return this.bridge[methodName].apply(this.bridge, arguments);
+  });
+}
+exports.actorBridgeWithSpec = actorBridgeWithSpec;
diff --git a/devtools/server/actors/css-properties.js b/devtools/server/actors/css-properties.js
new file mode 100644
index 000000000..d24c133d4
--- /dev/null
+++ b/devtools/server/actors/css-properties.js
@@ -0,0 +1,120 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cc, Ci } = require("chrome");
+
+loader.lazyGetter(this, "DOMUtils", () => {
+  return Cc["@mozilla.org/inspector/dom-utils;1"].getService(Ci.inIDOMUtils);
+});
+
+const protocol = require("devtools/shared/protocol");
+const { ActorClassWithSpec, Actor } = protocol;
+const { cssPropertiesSpec } = require("devtools/shared/specs/css-properties");
+const { CSS_PROPERTIES, CSS_TYPES } = require("devtools/shared/css/properties-db");
+const { cssColors } = require("devtools/shared/css/color-db");
+
+exports.CssPropertiesActor = ActorClassWithSpec(cssPropertiesSpec, {
+  typeName: "cssProperties",
+
+  initialize(conn, parent) {
+    Actor.prototype.initialize.call(this, conn);
+    this.parent = parent;
+  },
+
+  destroy() {
+    Actor.prototype.destroy.call(this);
+  },
+
+  getCSSDatabase() {
+    const properties = generateCssProperties();
+    const pseudoElements = DOMUtils.getCSSPseudoElementNames();
+
+    return { properties, pseudoElements };
+  }
+});
+
+/**
+ * Generate the CSS properties object. Every key is the property name, while
+ * the values are objects that contain information about that property.
+ *
+ * @return {Object}
+ */
+function generateCssProperties() {
+  const properties = {};
+  const propertyNames = DOMUtils.getCSSPropertyNames(DOMUtils.INCLUDE_ALIASES);
+  const colors = Object.keys(cssColors);
+
+  propertyNames.forEach(name => {
+    // Get the list of CSS types this property supports.
+    let supports = [];
+    for (let type in CSS_TYPES) {
+      if (safeCssPropertySupportsType(name, DOMUtils["TYPE_" + type])) {
+        supports.push(CSS_TYPES[type]);
+      }
+    }
+
+    // Don't send colors over RDP, these will be re-attached by the front.
+    let values = DOMUtils.getCSSValuesForProperty(name);
+    if (values.includes("aliceblue")) {
+      values = values.filter(x => !colors.includes(x));
+      values.unshift("COLOR");
+    }
+
+    let subproperties = DOMUtils.getSubpropertiesForCSSProperty(name);
+
+    // In order to maintain any backwards compatible changes when debugging older
+    // clients, take the definition from the static CSS properties database, and fill it
+    // in with the most recent property definition from the server.
+    const clientDefinition = CSS_PROPERTIES[name] || {};
+    const serverDefinition = {
+      isInherited: DOMUtils.isInheritedProperty(name),
+      values,
+      supports,
+      subproperties,
+    };
+    properties[name] = Object.assign(clientDefinition, serverDefinition);
+  });
+
+  return properties;
+}
+exports.generateCssProperties = generateCssProperties;
+
+/**
+ * Test if a CSS is property is known using server-code.
+ *
+ * @param {string} name
+ * @return {Boolean}
+ */
+function isCssPropertyKnown(name) {
+  try {
+    // If the property name is unknown, the cssPropertyIsShorthand
+    // will throw an exception.  But if it is known, no exception will
+    // be thrown; so we just ignore the return value.
+    DOMUtils.cssPropertyIsShorthand(name);
+    return true;
+  } catch (e) {
+    return false;
+  }
+}
+
+exports.isCssPropertyKnown = isCssPropertyKnown;
+
+/**
+ * A wrapper for DOMUtils.cssPropertySupportsType that ignores invalid
+ * properties.
+ *
+ * @param {String} name The property name.
+ * @param {number} type The type tested for support.
+ * @return {Boolean} Whether the property supports the type.
+ *        If the property is unknown, false is returned.
+ */
+function safeCssPropertySupportsType(name, type) {
+  try {
+    return DOMUtils.cssPropertySupportsType(name, type);
+  } catch (e) {
+    return false;
+  }
+}
diff --git a/devtools/server/actors/csscoverage.js b/devtools/server/actors/csscoverage.js
new file mode 100644
index 000000000..2f700656f
--- /dev/null
+++ b/devtools/server/actors/csscoverage.js
@@ -0,0 +1,726 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cc, Ci } = require("chrome");
+
+const Services = require("Services");
+const { XPCOMUtils } = require("resource://gre/modules/XPCOMUtils.jsm");
+
+const events = require("sdk/event/core");
+const protocol = require("devtools/shared/protocol");
+const { cssUsageSpec } = require("devtools/shared/specs/csscoverage");
+
+loader.lazyGetter(this, "DOMUtils", () => {
+  return Cc["@mozilla.org/inspector/dom-utils;1"].getService(Ci.inIDOMUtils);
+});
+loader.lazyRequireGetter(this, "stylesheets", "devtools/server/actors/stylesheets");
+loader.lazyRequireGetter(this, "prettifyCSS", "devtools/shared/inspector/css-logic", true);
+
+const CSSRule = Ci.nsIDOMCSSRule;
+
+const MAX_UNUSED_RULES = 10000;
+
+/**
+ * Allow: let foo = l10n.lookup("csscoverageFoo");
+ */
+const l10n = exports.l10n = {
+  _URI: "chrome://devtools-shared/locale/csscoverage.properties",
+  lookup: function (msg) {
+    if (this._stringBundle == null) {
+      this._stringBundle = Services.strings.createBundle(this._URI);
+    }
+    return this._stringBundle.GetStringFromName(msg);
+  }
+};
+
+/**
+ * CSSUsage manages the collection of CSS usage data.
+ * The core of a CSSUsage is a JSON-able data structure called _knownRules
+ * which looks like this:
+ * This records the CSSStyleRules and their usage.
+ * The format is:
+ *     Map({
+ *       <CSS-URL>|<START-LINE>|<START-COLUMN>: {
+ *         selectorText: <CSSStyleRule.selectorText>,
+ *         test: <simplify(CSSStyleRule.selectorText)>,
+ *         cssText: <CSSStyleRule.cssText>,
+ *         isUsed: <TRUE|FALSE>,
+ *         presentOn: Set([ <HTML-URL>, ... ]),
+ *         preLoadOn: Set([ <HTML-URL>, ... ]),
+ *         isError: <TRUE|FALSE>,
+ *       }
+ *     })
+ *
+ * For example:
+ *     this._knownRules = Map({
+ *       "http://eg.com/styles1.css|15|0": {
+ *         selectorText: "p.quote:hover",
+ *         test: "p.quote",
+ *         cssText: "p.quote { color: red; }",
+ *         isUsed: true,
+ *         presentOn: Set([ "http://eg.com/page1.html", ... ]),
+ *         preLoadOn: Set([ "http://eg.com/page1.html" ]),
+ *         isError: false,
+ *       }, ...
+ *     });
+ */
+var CSSUsageActor = protocol.ActorClassWithSpec(cssUsageSpec, {
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+
+    this._tabActor = tabActor;
+    this._running = false;
+
+    this._onTabLoad = this._onTabLoad.bind(this);
+    this._onChange = this._onChange.bind(this);
+
+    this._notifyOn = Ci.nsIWebProgress.NOTIFY_STATUS |
+                     Ci.nsIWebProgress.NOTIFY_STATE_ALL;
+  },
+
+  destroy: function () {
+    this._tabActor = undefined;
+
+    delete this._onTabLoad;
+    delete this._onChange;
+
+    protocol.Actor.prototype.destroy.call(this);
+  },
+
+  /**
+   * Begin recording usage data
+   * @param noreload It's best if we start by reloading the current page
+   * because that starts the test at a known point, but there could be reasons
+   * why we don't want to do that (e.g. the page contains state that will be
+   * lost across a reload)
+   */
+  start: function (noreload) {
+    if (this._running) {
+      throw new Error(l10n.lookup("csscoverageRunningError"));
+    }
+
+    this._isOneShot = false;
+    this._visitedPages = new Set();
+    this._knownRules = new Map();
+    this._running = true;
+    this._tooManyUnused = false;
+
+    this._progressListener = {
+      QueryInterface: XPCOMUtils.generateQI([ Ci.nsIWebProgressListener,
+                                              Ci.nsISupportsWeakReference ]),
+
+      onStateChange: (progress, request, flags, status) => {
+        let isStop = flags & Ci.nsIWebProgressListener.STATE_STOP;
+        let isWindow = flags & Ci.nsIWebProgressListener.STATE_IS_WINDOW;
+
+        if (isStop && isWindow) {
+          this._onTabLoad(progress.DOMWindow.document);
+        }
+      },
+
+      onLocationChange: () => {},
+      onProgressChange: () => {},
+      onSecurityChange: () => {},
+      onStatusChange: () => {},
+      destroy: () => {}
+    };
+
+    this._progress = this._tabActor.docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                                            .getInterface(Ci.nsIWebProgress);
+    this._progress.addProgressListener(this._progressListener, this._notifyOn);
+
+    if (noreload) {
+      // If we're not starting by reloading the page, then pretend that onload
+      // has just happened.
+      this._onTabLoad(this._tabActor.window.document);
+    } else {
+      this._tabActor.window.location.reload();
+    }
+
+    events.emit(this, "state-change", { isRunning: true });
+  },
+
+  /**
+   * Cease recording usage data
+   */
+  stop: function () {
+    if (!this._running) {
+      throw new Error(l10n.lookup("csscoverageNotRunningError"));
+    }
+
+    this._progress.removeProgressListener(this._progressListener, this._notifyOn);
+    this._progress = undefined;
+
+    this._running = false;
+    events.emit(this, "state-change", { isRunning: false });
+  },
+
+  /**
+   * Start/stop recording usage data depending on what we're currently doing.
+   */
+  toggle: function () {
+    return this._running ? this.stop() : this.start();
+  },
+
+  /**
+   * Running start() quickly followed by stop() does a bunch of unnecessary
+   * work, so this cuts all that out
+   */
+  oneshot: function () {
+    if (this._running) {
+      throw new Error(l10n.lookup("csscoverageRunningError"));
+    }
+
+    this._isOneShot = true;
+    this._visitedPages = new Set();
+    this._knownRules = new Map();
+
+    this._populateKnownRules(this._tabActor.window.document);
+    this._updateUsage(this._tabActor.window.document, false);
+  },
+
+  /**
+   * Called by the ProgressListener to simulate a "load" event
+   */
+  _onTabLoad: function (document) {
+    this._populateKnownRules(document);
+    this._updateUsage(document, true);
+
+    this._observeMutations(document);
+  },
+
+  /**
+   * Setup a MutationObserver on the current document
+   */
+  _observeMutations: function (document) {
+    let MutationObserver = document.defaultView.MutationObserver;
+    let observer = new MutationObserver(mutations => {
+      // It's possible that one of the mutations in this list adds a 'use' of
+      // a CSS rule, and another takes it away. See Bug 1010189
+      this._onChange(document);
+    });
+
+    observer.observe(document, {
+      attributes: true,
+      childList: true,
+      characterData: false,
+      subtree: true
+    });
+  },
+
+  /**
+   * Event handler for whenever we think the page has changed in a way that
+   * means the CSS usage might have changed.
+   */
+  _onChange: function (document) {
+    // Ignore changes pre 'load'
+    if (!this._visitedPages.has(getURL(document))) {
+      return;
+    }
+    this._updateUsage(document, false);
+  },
+
+  /**
+   * Called whenever we think the list of stylesheets might have changed so
+   * we can update the list of rules that we should be checking
+   */
+  _populateKnownRules: function (document) {
+    let url = getURL(document);
+    this._visitedPages.add(url);
+    // Go through all the rules in the current sheets adding them to knownRules
+    // if needed and adding the current url to the list of pages they're on
+    for (let rule of getAllSelectorRules(document)) {
+      let ruleId = ruleToId(rule);
+      let ruleData = this._knownRules.get(ruleId);
+      if (ruleData == null) {
+        ruleData = {
+          selectorText: rule.selectorText,
+          cssText: rule.cssText,
+          test: getTestSelector(rule.selectorText),
+          isUsed: false,
+          presentOn: new Set(),
+          preLoadOn: new Set(),
+          isError: false
+        };
+        this._knownRules.set(ruleId, ruleData);
+      }
+
+      ruleData.presentOn.add(url);
+    }
+  },
+
+  /**
+   * Update knownRules with usage information from the current page
+   */
+  _updateUsage: function (document, isLoad) {
+    let qsaCount = 0;
+
+    // Update this._data with matches to say 'used at load time' by sheet X
+    let url = getURL(document);
+
+    for (let [ , ruleData ] of this._knownRules) {
+      // If it broke before, don't try again selectors don't change
+      if (ruleData.isError) {
+        continue;
+      }
+
+      // If it's used somewhere already, don't bother checking again unless
+      // this is a load event in which case we need to add preLoadOn
+      if (!isLoad && ruleData.isUsed) {
+        continue;
+      }
+
+      // Ignore rules that are not present on this page
+      if (!ruleData.presentOn.has(url)) {
+        continue;
+      }
+
+      qsaCount++;
+      if (qsaCount > MAX_UNUSED_RULES) {
+        console.error("Too many unused rules on " + url + " ");
+        this._tooManyUnused = true;
+        continue;
+      }
+
+      try {
+        let match = document.querySelector(ruleData.test);
+        if (match != null) {
+          ruleData.isUsed = true;
+          if (isLoad) {
+            ruleData.preLoadOn.add(url);
+          }
+        }
+      } catch (ex) {
+        ruleData.isError = true;
+      }
+    }
+  },
+
+  /**
+   * Returns a JSONable structure designed to help marking up the style editor,
+   * which describes the CSS selector usage.
+   * Example:
+   *   [
+   *     {
+   *       selectorText: "p#content",
+   *       usage: "unused|used",
+   *       start: { line: 3, column: 0 },
+   *     },
+   *     ...
+   *   ]
+   */
+  createEditorReport: function (url) {
+    if (this._knownRules == null) {
+      return { reports: [] };
+    }
+
+    let reports = [];
+    for (let [ruleId, ruleData] of this._knownRules) {
+      let { url: ruleUrl, line, column } = deconstructRuleId(ruleId);
+      if (ruleUrl !== url || ruleData.isUsed) {
+        continue;
+      }
+
+      let ruleReport = {
+        selectorText: ruleData.selectorText,
+        start: { line: line, column: column }
+      };
+
+      if (ruleData.end) {
+        ruleReport.end = ruleData.end;
+      }
+
+      reports.push(ruleReport);
+    }
+
+    return { reports: reports };
+  },
+
+  /**
+   * Compute the stylesheet URL and delegate the report creation to createEditorReport.
+   * See createEditorReport documentation.
+   *
+   * @param {StyleSheetActor} stylesheetActor
+   *        the stylesheet actor for which the coverage report should be generated.
+   */
+  createEditorReportForSheet: function (stylesheetActor) {
+    let url = sheetToUrl(stylesheetActor.rawSheet);
+    return this.createEditorReport(url);
+  },
+
+  /**
+   * Returns a JSONable structure designed for the page report which shows
+   * the recommended changes to a page.
+   *
+   * "preload" means that a rule is used before the load event happens, which
+   * means that the page could by optimized by placing it in a <style> element
+   * at the top of the page, moving the <link> elements to the bottom.
+   *
+   * Example:
+   *   {
+   *     preload: [
+   *       {
+   *         url: "http://example.org/page1.html",
+   *         shortUrl: "page1.html",
+   *         rules: [
+   *           {
+   *             url: "http://example.org/style1.css",
+   *             shortUrl: "style1.css",
+   *             start: { line: 3, column: 4 },
+   *             selectorText: "p#content",
+   *             formattedCssText: "p#content {\n  color: red;\n }\n"
+   *          },
+   *          ...
+   *         ]
+   *       }
+   *     ],
+   *     unused: [
+   *       {
+   *         url: "http://example.org/style1.css",
+   *         shortUrl: "style1.css",
+   *         rules: [ ... ]
+   *       }
+   *     ]
+   *   }
+   */
+  createPageReport: function () {
+    if (this._running) {
+      throw new Error(l10n.lookup("csscoverageRunningError"));
+    }
+
+    if (this._visitedPages == null) {
+      throw new Error(l10n.lookup("csscoverageNotRunError"));
+    }
+
+    if (this._isOneShot) {
+      throw new Error(l10n.lookup("csscoverageOneShotReportError"));
+    }
+
+    // Helper function to create a JSONable data structure representing a rule
+    const ruleToRuleReport = function (rule, ruleData) {
+      return {
+        url: rule.url,
+        shortUrl: rule.url.split("/").slice(-1)[0],
+        start: { line: rule.line, column: rule.column },
+        selectorText: ruleData.selectorText,
+        formattedCssText: prettifyCSS(ruleData.cssText)
+      };
+    };
+
+    // A count of each type of rule for the bar chart
+    let summary = { used: 0, unused: 0, preload: 0 };
+
+    // Create the set of the unused rules
+    let unusedMap = new Map();
+    for (let [ruleId, ruleData] of this._knownRules) {
+      let rule = deconstructRuleId(ruleId);
+      let rules = unusedMap.get(rule.url);
+      if (rules == null) {
+        rules = [];
+        unusedMap.set(rule.url, rules);
+      }
+      if (!ruleData.isUsed) {
+        let ruleReport = ruleToRuleReport(rule, ruleData);
+        rules.push(ruleReport);
+      } else {
+        summary.unused++;
+      }
+    }
+    let unused = [];
+    for (let [url, rules] of unusedMap) {
+      unused.push({
+        url: url,
+        shortUrl: url.split("/").slice(-1),
+        rules: rules
+      });
+    }
+
+    // Create the set of rules that could be pre-loaded
+    let preload = [];
+    for (let url of this._visitedPages) {
+      let page = {
+        url: url,
+        shortUrl: url.split("/").slice(-1),
+        rules: []
+      };
+
+      for (let [ruleId, ruleData] of this._knownRules) {
+        if (ruleData.preLoadOn.has(url)) {
+          let rule = deconstructRuleId(ruleId);
+          let ruleReport = ruleToRuleReport(rule, ruleData);
+          page.rules.push(ruleReport);
+          summary.preload++;
+        } else {
+          summary.used++;
+        }
+      }
+
+      if (page.rules.length > 0) {
+        preload.push(page);
+      }
+    }
+
+    return {
+      summary: summary,
+      preload: preload,
+      unused: unused
+    };
+  },
+
+  /**
+   * For testing only. What pages did we visit.
+   */
+  _testOnlyVisitedPages: function () {
+    return [...this._visitedPages];
+  },
+});
+
+exports.CSSUsageActor = CSSUsageActor;
+
+/**
+ * Generator that filters the CSSRules out of _getAllRules so it only
+ * iterates over the CSSStyleRules
+ */
+function* getAllSelectorRules(document) {
+  for (let rule of getAllRules(document)) {
+    if (rule.type === CSSRule.STYLE_RULE && rule.selectorText !== "") {
+      yield rule;
+    }
+  }
+}
+
+/**
+ * Generator to iterate over the CSSRules in all the stylesheets the
+ * current document (i.e. it includes import rules, media rules, etc)
+ */
+function* getAllRules(document) {
+  // sheets is an array of the <link> and <style> element in this document
+  let sheets = getAllSheets(document);
+  for (let i = 0; i < sheets.length; i++) {
+    for (let j = 0; j < sheets[i].cssRules.length; j++) {
+      yield sheets[i].cssRules[j];
+    }
+  }
+}
+
+/**
+ * Get an array of all the stylesheets that affect this document. That means
+ * the <link> and <style> based sheets, and the @imported sheets (recursively)
+ * but not the sheets in nested frames.
+ */
+function getAllSheets(document) {
+  // sheets is an array of the <link> and <style> element in this document
+  let sheets = Array.slice(document.styleSheets);
+  // Add @imported sheets
+  for (let i = 0; i < sheets.length; i++) {
+    let subSheets = getImportedSheets(sheets[i]);
+    sheets = sheets.concat(...subSheets);
+  }
+  return sheets;
+}
+
+/**
+ * Recursively find @import rules in the given stylesheet.
+ * We're relying on the browser giving rule.styleSheet == null to resolve
+ * @import loops
+ */
+function getImportedSheets(stylesheet) {
+  let sheets = [];
+  for (let i = 0; i < stylesheet.cssRules.length; i++) {
+    let rule = stylesheet.cssRules[i];
+    // rule.styleSheet == null with duplicate @imports for the same URL.
+    if (rule.type === CSSRule.IMPORT_RULE && rule.styleSheet != null) {
+      sheets.push(rule.styleSheet);
+      let subSheets = getImportedSheets(rule.styleSheet);
+      sheets = sheets.concat(...subSheets);
+    }
+  }
+  return sheets;
+}
+
+/**
+ * Get a unique identifier for a rule. This is currently the string
+ * <CSS-URL>|<START-LINE>|<START-COLUMN>
+ * @see deconstructRuleId(ruleId)
+ */
+function ruleToId(rule) {
+  let line = DOMUtils.getRelativeRuleLine(rule);
+  let column = DOMUtils.getRuleColumn(rule);
+  return sheetToUrl(rule.parentStyleSheet) + "|" + line + "|" + column;
+}
+
+/**
+ * Convert a ruleId to an object with { url, line, column } properties
+ * @see ruleToId(rule)
+ */
+const deconstructRuleId = exports.deconstructRuleId = function (ruleId) {
+  let split = ruleId.split("|");
+  if (split.length > 3) {
+    let replace = split.slice(0, split.length - 3 + 1).join("|");
+    split.splice(0, split.length - 3 + 1, replace);
+  }
+  let [ url, line, column ] = split;
+  return {
+    url: url,
+    line: parseInt(line, 10),
+    column: parseInt(column, 10)
+  };
+};
+
+/**
+ * We're only interested in the origin and pathname, because changes to the
+ * username, password, hash, or query string probably don't significantly
+ * change the CSS usage properties of a page.
+ * @param document
+ */
+const getURL = exports.getURL = function (document) {
+  let url = new document.defaultView.URL(document.documentURI);
+  return url == "about:blank" ? "" : "" + url.origin + url.pathname;
+};
+
+/**
+ * Pseudo class handling constants:
+ * We split pseudo-classes into a number of categories so we can decide how we
+ * should match them. See getTestSelector for how we use these constants.
+ *
+ * @see http://dev.w3.org/csswg/selectors4/#overview
+ * @see https://developer.mozilla.org/en-US/docs/tag/CSS%20Pseudo-class
+ * @see https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-elements
+ */
+
+/**
+ * Category 1: Pseudo-classes that depend on external browser/OS state
+ * This includes things like the time, locale, position of mouse/caret/window,
+ * contents of browser history, etc. These can be hard to mimic.
+ * Action: Remove from selectors
+ */
+const SEL_EXTERNAL = [
+  "active", "active-drop", "current", "dir", "focus", "future", "hover",
+  "invalid-drop", "lang", "past", "placeholder-shown", "target", "valid-drop",
+  "visited"
+];
+
+/**
+ * Category 2: Pseudo-classes that depend on user-input state
+ * These are pseudo-classes that arguably *should* be covered by unit tests but
+ * which probably aren't and which are unlikely to be covered by manual tests.
+ * We're currently stripping them out,
+ * Action: Remove from selectors (but consider future command line flag to
+ * enable them in the future. e.g. 'csscoverage start --strict')
+ */
+const SEL_FORM = [
+  "checked", "default", "disabled", "enabled", "fullscreen", "in-range",
+  "indeterminate", "invalid", "optional", "out-of-range", "required", "valid"
+];
+
+/**
+ * Category 3: Pseudo-elements
+ * querySelectorAll doesn't return matches with pseudo-elements because there
+ * is no element to match (they're pseudo) so we have to remove them all.
+ * (See http://codepen.io/joewalker/pen/sanDw for a demo)
+ * Action: Remove from selectors (including deprecated single colon versions)
+ */
+const SEL_ELEMENT = [
+  "after", "before", "first-letter", "first-line", "selection"
+];
+
+/**
+ * Category 4: Structural pseudo-classes
+ * This is a category defined by the spec (also called tree-structural and
+ * grid-structural) for selection based on relative position in the document
+ * tree that cannot be represented by other simple selectors or combinators.
+ * Action: Require a page-match
+ */
+const SEL_STRUCTURAL = [
+  "empty", "first-child", "first-of-type", "last-child", "last-of-type",
+  "nth-column", "nth-last-column", "nth-child", "nth-last-child",
+  "nth-last-of-type", "nth-of-type", "only-child", "only-of-type", "root"
+];
+
+/**
+ * Category 4a: Semi-structural pseudo-classes
+ * These are not structural according to the spec, but act nevertheless on
+ * information in the document tree.
+ * Action: Require a page-match
+ */
+const SEL_SEMI = [ "any-link", "link", "read-only", "read-write", "scope" ];
+
+/**
+ * Category 5: Combining pseudo-classes
+ * has(), not() etc join selectors together in various ways. We take care when
+ * removing pseudo-classes to convert "not(:hover)" into "not(*)" and so on.
+ * With these changes the combining pseudo-classes should probably stand on
+ * their own.
+ * Action: Require a page-match
+ */
+const SEL_COMBINING = [ "not", "has", "matches" ];
+
+/**
+ * Category 6: Media pseudo-classes
+ * Pseudo-classes that should be ignored because they're only relevant to
+ * media queries
+ * Action: Don't need removing from selectors as they appear in media queries
+ */
+const SEL_MEDIA = [ "blank", "first", "left", "right" ];
+
+/**
+ * A test selector is a reduced form of a selector that we actually test
+ * against. This code strips out pseudo-elements and some pseudo-classes that
+ * we think should not have to match in order for the selector to be relevant.
+ */
+function getTestSelector(selector) {
+  let replacement = selector;
+  let replaceSelector = pseudo => {
+    replacement = replacement.replace(" :" + pseudo, " *")
+                             .replace("(:" + pseudo, "(*")
+                             .replace(":" + pseudo, "");
+  };
+
+  SEL_EXTERNAL.forEach(replaceSelector);
+  SEL_FORM.forEach(replaceSelector);
+  SEL_ELEMENT.forEach(replaceSelector);
+
+  // Pseudo elements work in : and :: forms
+  SEL_ELEMENT.forEach(pseudo => {
+    replacement = replacement.replace("::" + pseudo, "");
+  });
+
+  return replacement;
+}
+
+/**
+ * I've documented all known pseudo-classes above for 2 reasons: To allow
+ * checking logic and what might be missing, but also to allow a unit test
+ * that fetches the list of supported pseudo-classes and pseudo-elements from
+ * the platform and check that they were all represented here.
+ */
+exports.SEL_ALL = [
+  SEL_EXTERNAL, SEL_FORM, SEL_ELEMENT, SEL_STRUCTURAL, SEL_SEMI,
+  SEL_COMBINING, SEL_MEDIA
+].reduce(function (prev, curr) {
+  return prev.concat(curr);
+}, []);
+
+/**
+ * Find a URL for a given stylesheet
+ * @param {StyleSheet} stylesheet raw stylesheet
+ */
+const sheetToUrl = function (stylesheet) {
+  // For <link> elements
+  if (stylesheet.href) {
+    return stylesheet.href;
+  }
+
+  // For <style> elements
+  if (stylesheet.ownerNode) {
+    let document = stylesheet.ownerNode.ownerDocument;
+    let sheets = [...document.querySelectorAll("style")];
+    let index = sheets.indexOf(stylesheet.ownerNode);
+    return getURL(document) + " → <style> index " + index;
+  }
+
+  throw new Error("Unknown sheet source");
+};
diff --git a/devtools/server/actors/device.js b/devtools/server/actors/device.js
new file mode 100644
index 000000000..bf400913a
--- /dev/null
+++ b/devtools/server/actors/device.js
@@ -0,0 +1,70 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {Ci} = require("chrome");
+const Services = require("Services");
+const protocol = require("devtools/shared/protocol");
+const promise = require("promise");
+const {LongStringActor} = require("devtools/server/actors/string");
+const {DebuggerServer} = require("devtools/server/main");
+const {getSystemInfo, getSetting} = require("devtools/shared/system");
+const {deviceSpec} = require("devtools/shared/specs/device");
+const FileReader = require("FileReader");
+const {PermissionsTable} = require("resource://gre/modules/PermissionsTable.jsm");
+
+var DeviceActor = exports.DeviceActor = protocol.ActorClassWithSpec(deviceSpec, {
+  _desc: null,
+
+  getDescription: function () {
+    return getSystemInfo();
+  },
+
+  getWallpaper: function () {
+    let deferred = promise.defer();
+    getSetting("wallpaper.image").then((blob) => {
+      let reader = new FileReader();
+      let conn = this.conn;
+      reader.addEventListener("load", function () {
+        let str = new LongStringActor(conn, reader.result);
+        deferred.resolve(str);
+      });
+      reader.addEventListener("error", function () {
+        deferred.reject(reader.error);
+      });
+      reader.readAsDataURL(blob);
+    });
+    return deferred.promise;
+  },
+
+  screenshotToDataURL: function () {
+    let window = Services.wm.getMostRecentWindow(DebuggerServer.chromeWindowType);
+    var devicePixelRatio = window.devicePixelRatio;
+    let canvas = window.document.createElementNS("http://www.w3.org/1999/xhtml", "canvas");
+    let width = window.innerWidth;
+    let height = window.innerHeight;
+    canvas.setAttribute("width", Math.round(width * devicePixelRatio));
+    canvas.setAttribute("height", Math.round(height * devicePixelRatio));
+    let context = canvas.getContext("2d");
+    let flags =
+          context.DRAWWINDOW_DRAW_CARET |
+          context.DRAWWINDOW_DRAW_VIEW |
+          context.DRAWWINDOW_USE_WIDGET_LAYERS;
+    context.scale(devicePixelRatio, devicePixelRatio);
+    context.drawWindow(window, 0, 0, width, height, "rgb(255,255,255)", flags);
+    let dataURL = canvas.toDataURL("image/png");
+    return new LongStringActor(this.conn, dataURL);
+  },
+
+  getRawPermissionsTable: function () {
+    return {
+      rawPermissionsTable: PermissionsTable,
+      UNKNOWN_ACTION: Ci.nsIPermissionManager.UNKNOWN_ACTION,
+      ALLOW_ACTION: Ci.nsIPermissionManager.ALLOW_ACTION,
+      DENY_ACTION: Ci.nsIPermissionManager.DENY_ACTION,
+      PROMPT_ACTION: Ci.nsIPermissionManager.PROMPT_ACTION
+    };
+  }
+});
diff --git a/devtools/server/actors/director-manager.js b/devtools/server/actors/director-manager.js
new file mode 100644
index 000000000..027a456db
--- /dev/null
+++ b/devtools/server/actors/director-manager.js
@@ -0,0 +1,615 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const events = require("sdk/event/core");
+const protocol = require("devtools/shared/protocol");
+
+const { Cu, Ci } = require("chrome");
+
+const { on, once, off, emit } = events;
+const { method, Arg, Option, RetVal, types } = protocol;
+
+const { sandbox, evaluate } = require("sdk/loader/sandbox");
+const { Class } = require("sdk/core/heritage");
+
+const { PlainTextConsole } = require("sdk/console/plain-text");
+
+const { DirectorRegistry } = require("./director-registry");
+
+const {
+  messagePortSpec,
+  directorManagerSpec,
+  directorScriptSpec,
+} = require("devtools/shared/specs/director-manager");
+
+/**
+ * Error Messages
+ */
+
+const ERR_MESSAGEPORT_FINALIZED = "message port finalized";
+
+const ERR_DIRECTOR_UNKNOWN_SCRIPTID = "unkown director-script id";
+const ERR_DIRECTOR_UNINSTALLED_SCRIPTID = "uninstalled director-script id";
+
+/**
+ * A MessagePort Actor allowing communication through messageport events
+ * over the remote debugging protocol.
+ */
+var MessagePortActor = exports.MessagePortActor = protocol.ActorClassWithSpec(messagePortSpec, {
+  /**
+   * Create a MessagePort actor.
+   *
+   * @param DebuggerServerConnection conn
+   *        The server connection.
+   * @param MessagePort port
+   *        The wrapped MessagePort.
+   */
+  initialize: function (conn, port) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+
+    // NOTE: can't get a weak reference because we need to subscribe events
+    // using port.onmessage or addEventListener
+    this.port = port;
+  },
+
+  destroy: function (conn) {
+    protocol.Actor.prototype.destroy.call(this, conn);
+    this.finalize();
+  },
+
+  /**
+   * Sends a message on the wrapped message port.
+   *
+   * @param Object msg
+   *        The JSON serializable message event payload
+   */
+  postMessage: function (msg) {
+    if (!this.port) {
+      console.error(ERR_MESSAGEPORT_FINALIZED);
+      return;
+    }
+
+    this.port.postMessage(msg);
+  },
+
+  /**
+   * Starts to receive and send queued messages on this message port.
+   */
+  start: function () {
+    if (!this.port) {
+      console.error(ERR_MESSAGEPORT_FINALIZED);
+      return;
+    }
+
+    // NOTE: set port.onmessage to a function is an implicit start
+    // and starts to send queued messages.
+    // On the client side we should set MessagePortClient.onmessage
+    // to a setter which register an handler to the message event
+    // and call the actor start method to start receiving messages
+    // from the MessagePort's queue.
+    this.port.onmessage = (evt) => {
+      var ports;
+
+      // TODO: test these wrapped ports
+      if (Array.isArray(evt.ports)) {
+        ports = evt.ports.map((port) => {
+          let actor = new MessagePortActor(this.conn, port);
+          this.manage(actor);
+          return actor;
+        });
+      }
+
+      emit(this, "message", {
+        isTrusted: evt.isTrusted,
+        data: evt.data,
+        origin: evt.origin,
+        lastEventId: evt.lastEventId,
+        source: this,
+        ports: ports
+      });
+    };
+  },
+
+  /**
+   * Starts to receive and send queued messages on this message port, or
+   * raise an exception if the port is null
+   */
+  close: function () {
+    if (!this.port) {
+      console.error(ERR_MESSAGEPORT_FINALIZED);
+      return;
+    }
+
+    try {
+      this.port.onmessage = null;
+      this.port.close();
+    } catch (e) {
+      // The port might be a dead object
+      console.error(e);
+    }
+  },
+
+  finalize: function () {
+    this.close();
+    this.port = null;
+  },
+});
+
+/**
+ * The Director Script Actor manage javascript code running in a non-privileged sandbox with the same
+ * privileges of the target global (browser tab or a firefox os app).
+ *
+ * After retrieving an instance of this actor (from the tab director actor), you'll need to set it up
+ * by calling setup().
+ *
+ * After the setup, this actor will automatically attach/detach the content script (and optionally a
+ * directly connect the debugger client and the content script using a MessageChannel) on tab
+ * navigation.
+ */
+var DirectorScriptActor = exports.DirectorScriptActor = protocol.ActorClassWithSpec(directorScriptSpec, {
+  /**
+   * Creates the director script actor
+   *
+   * @param DebuggerServerConnection conn
+   *        The server connection.
+   * @param Actor tabActor
+   *        The tab (or root) actor.
+   * @param String scriptId
+   *        The director-script id.
+   * @param String scriptCode
+   *        The director-script javascript source.
+   * @param Object scriptOptions
+   *        The director-script options object.
+   */
+  initialize: function (conn, tabActor, { scriptId, scriptCode, scriptOptions }) {
+    protocol.Actor.prototype.initialize.call(this, conn, tabActor);
+
+    this.tabActor = tabActor;
+
+    this._scriptId = scriptId;
+    this._scriptCode = scriptCode;
+    this._scriptOptions = scriptOptions;
+    this._setupCalled = false;
+
+    this._onGlobalCreated = this._onGlobalCreated.bind(this);
+    this._onGlobalDestroyed = this._onGlobalDestroyed.bind(this);
+  },
+  destroy: function (conn) {
+    protocol.Actor.prototype.destroy.call(this, conn);
+
+    this.finalize();
+  },
+
+  /**
+   * Starts listening to the tab global created, in order to create the director-script sandbox
+   * using the configured scriptCode, attached/detached automatically to the tab
+   * window on tab navigation.
+   *
+   * @param Boolean reload
+   *        attach the page immediately or reload it first.
+   * @param Boolean skipAttach
+   *        skip the attach
+   */
+  setup: function ({ reload, skipAttach }) {
+    if (this._setupCalled) {
+      // do nothing
+      return;
+    }
+
+    this._setupCalled = true;
+
+    on(this.tabActor, "window-ready", this._onGlobalCreated);
+    on(this.tabActor, "window-destroyed", this._onGlobalDestroyed);
+
+    // optional skip attach (needed by director-manager for director scripts bulk activation)
+    if (skipAttach) {
+      return;
+    }
+
+    if (reload) {
+      this.window.location.reload();
+    } else {
+      // fake a global created event to attach without reload
+      this._onGlobalCreated({ id: getWindowID(this.window), window: this.window, isTopLevel: true });
+    }
+  },
+
+  /**
+   * Get the attached MessagePort actor if any
+   */
+  getMessagePort: function () {
+    return this._messagePortActor;
+  },
+
+  /**
+   * Stop listening for document global changes, destroy the content worker and puts
+   * this actor to hibernation.
+   */
+  finalize: function () {
+    if (!this._setupCalled) {
+      return;
+    }
+
+    off(this.tabActor, "window-ready", this._onGlobalCreated);
+    off(this.tabActor, "window-destroyed", this._onGlobalDestroyed);
+
+    this._onGlobalDestroyed({ id: this._lastAttachedWinId });
+
+    this._setupCalled = false;
+  },
+
+  // local helpers
+  get window() {
+    return this.tabActor.window;
+  },
+
+  /* event handlers */
+  _onGlobalCreated: function ({ id, window, isTopLevel }) {
+    if (!isTopLevel) {
+      // filter iframes
+      return;
+    }
+
+    try {
+      if (this._lastAttachedWinId) {
+        // if we have received a global created without a previous global destroyed,
+        // it's time to cleanup the previous state
+        this._onGlobalDestroyed(this._lastAttachedWinId);
+      }
+
+      // TODO: check if we want to share a single sandbox per global
+      //       for multiple debugger clients
+
+      // create & attach the new sandbox
+      this._scriptSandbox = new DirectorScriptSandbox({
+        scriptId: this._scriptId,
+        scriptCode: this._scriptCode,
+        scriptOptions: this._scriptOptions
+      });
+
+      // attach the global window
+      this._lastAttachedWinId = id;
+      var port = this._scriptSandbox.attach(window, id);
+      this._onDirectorScriptAttach(window, port);
+    } catch (e) {
+      this._onDirectorScriptError(e);
+    }
+  },
+  _onGlobalDestroyed: function ({ id }) {
+    if (id !== this._lastAttachedWinId) {
+       // filter destroyed globals
+      return;
+    }
+
+     // unmanage and cleanup the messageport actor
+    if (this._messagePortActor) {
+      this.unmanage(this._messagePortActor);
+      this._messagePortActor = null;
+    }
+
+     // NOTE: destroy here the old worker
+    if (this._scriptSandbox) {
+      this._scriptSandbox.destroy(this._onDirectorScriptError.bind(this));
+
+       // send a detach event to the debugger client
+      emit(this, "detach", {
+        directorScriptId: this._scriptId,
+        innerId: this._lastAttachedWinId
+      });
+
+      this._lastAttachedWinId = null;
+      this._scriptSandbox = null;
+    }
+  },
+  _onDirectorScriptError: function (error) {
+    // route the content script error to the debugger client
+    if (error) {
+      // prevents silent director-script-errors
+      console.error("director-script-error", error);
+      // route errors to debugger server clients
+      emit(this, "error", {
+        directorScriptId: this._scriptId,
+        message: error.toString(),
+        stack: error.stack,
+        fileName: error.fileName,
+        lineNumber: error.lineNumber,
+        columnNumber: error.columnNumber
+      });
+    }
+  },
+  _onDirectorScriptAttach: function (window, port) {
+    let portActor = new MessagePortActor(this.conn, port);
+    this.manage(portActor);
+    this._messagePortActor = portActor;
+
+    emit(this, "attach", {
+      directorScriptId: this._scriptId,
+      url: (window && window.location) ? window.location.toString() : "",
+      innerId: this._lastAttachedWinId,
+      port: this._messagePortActor
+    });
+  }
+});
+
+/**
+ * The DirectorManager Actor is a tab actor which manages enabling/disabling director scripts.
+ */
+const DirectorManagerActor = exports.DirectorManagerActor = protocol.ActorClassWithSpec(directorManagerSpec, {
+  /* init & destroy methods */
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.tabActor = tabActor;
+    this._directorScriptActorsMap = new Map();
+  },
+  destroy: function (conn) {
+    protocol.Actor.prototype.destroy.call(this, conn);
+    this.finalize();
+  },
+
+  /**
+   * Retrieves the list of installed director-scripts.
+   */
+  list: function () {
+    let enabledScriptIds = [...this._directorScriptActorsMap.keys()];
+
+    return {
+      installed: DirectorRegistry.list(),
+      enabled: enabledScriptIds
+    };
+  },
+
+  /**
+   * Bulk enabling director-scripts.
+   *
+   * @param Array[String] selectedIds
+   *        The list of director-script ids to be enabled,
+   *        ["*"] will activate all the installed director-scripts
+   * @param Boolean reload
+   *        optionally reload the target window
+   */
+  enableByScriptIds: function (selectedIds, { reload }) {
+    if (selectedIds && selectedIds.length === 0) {
+      // filtered all director scripts ids
+      return;
+    }
+
+    for (let scriptId of DirectorRegistry.list()) {
+      // filter director script ids
+      if (selectedIds.indexOf("*") < 0 &&
+          selectedIds.indexOf(scriptId) < 0) {
+        continue;
+      }
+
+      let actor = this.getByScriptId(scriptId);
+
+      // skip attach if reload is true (activated director scripts
+      // will be automatically attached on the final reload)
+      actor.setup({ reload: false, skipAttach: reload });
+    }
+
+    if (reload) {
+      this.tabActor.window.location.reload();
+    }
+  },
+
+  /**
+   * Bulk disabling director-scripts.
+   *
+   * @param Array[String] selectedIds
+   *        The list of director-script ids to be disable,
+   *        ["*"] will de-activate all the enable director-scripts
+   * @param Boolean reload
+   *        optionally reload the target window
+   */
+  disableByScriptIds: function (selectedIds, { reload }) {
+    if (selectedIds && selectedIds.length === 0) {
+      // filtered all director scripts ids
+      return;
+    }
+
+    for (let scriptId of this._directorScriptActorsMap.keys()) {
+      // filter director script ids
+      if (selectedIds.indexOf("*") < 0 &&
+          selectedIds.indexOf(scriptId) < 0) {
+        continue;
+      }
+
+      let actor = this._directorScriptActorsMap.get(scriptId);
+      this._directorScriptActorsMap.delete(scriptId);
+
+      // finalize the actor (which will produce director-script-detach event)
+      actor.finalize();
+      // unsubscribe event handlers on the disabled actor
+      off(actor);
+
+      this.unmanage(actor);
+    }
+
+    if (reload) {
+      this.tabActor.window.location.reload();
+    }
+  },
+
+  /**
+   * Retrieves the actor instance of an installed director-script
+   * (and create the actor instance if it doesn't exists yet).
+   */
+  getByScriptId: function (scriptId) {
+    var id = scriptId;
+    // raise an unknown director-script id exception
+    if (!DirectorRegistry.checkInstalled(id)) {
+      console.error(ERR_DIRECTOR_UNKNOWN_SCRIPTID, id);
+      throw Error(ERR_DIRECTOR_UNKNOWN_SCRIPTID);
+    }
+
+    // get a previous created actor instance
+    let actor = this._directorScriptActorsMap.get(id);
+
+    // create a new actor instance
+    if (!actor) {
+      let directorScriptDefinition = DirectorRegistry.get(id);
+
+      // test lazy director-script (e.g. uninstalled in the parent process)
+      if (!directorScriptDefinition) {
+
+        console.error(ERR_DIRECTOR_UNINSTALLED_SCRIPTID, id);
+        throw Error(ERR_DIRECTOR_UNINSTALLED_SCRIPTID);
+      }
+
+      actor = new DirectorScriptActor(this.conn, this.tabActor, directorScriptDefinition);
+      this._directorScriptActorsMap.set(id, actor);
+
+      on(actor, "error", emit.bind(null, this, "director-script-error"));
+      on(actor, "attach", emit.bind(null, this, "director-script-attach"));
+      on(actor, "detach", emit.bind(null, this, "director-script-detach"));
+
+      this.manage(actor);
+    }
+
+    return actor;
+  },
+
+  finalize: function () {
+    this.disableByScriptIds(["*"], false);
+  }
+});
+
+/* private helpers */
+
+/**
+ * DirectorScriptSandbox is a private utility class, which attach a non-priviliged sandbox
+ * to a target window.
+ */
+const DirectorScriptSandbox = Class({
+  initialize: function ({scriptId, scriptCode, scriptOptions}) {
+    this._scriptId = scriptId;
+    this._scriptCode = scriptCode;
+    this._scriptOptions = scriptOptions;
+  },
+
+  attach: function (window, innerId) {
+    this._innerId = innerId,
+    this._window = window;
+    this._proto = Cu.createObjectIn(this._window);
+
+    var id = this._scriptId;
+    var uri = this._scriptCode;
+
+    this._sandbox = sandbox(window, {
+      sandboxName: uri,
+      sandboxPrototype: this._proto,
+      sameZoneAs: window,
+      wantXrays: true,
+      wantComponents: false,
+      wantExportHelpers: false,
+      metadata: {
+        URI: uri,
+        addonID: id,
+        SDKDirectorScript: true,
+        "inner-window-id": innerId
+      }
+    });
+
+    // create a CommonJS module object which match the interface from addon-sdk
+    // (addon-sdk/sources/lib/toolkit/loader.js#L678-L686)
+    var module = Cu.cloneInto(Object.create(null, {
+      id: { enumerable: true, value: id },
+      uri: { enumerable: true, value: uri },
+      exports: { enumerable: true, value: Cu.createObjectIn(this._sandbox) }
+    }), this._sandbox);
+
+    // create a console API object
+    let directorScriptConsole = new PlainTextConsole(null, this._innerId);
+
+    // inject CommonJS module globals into the sandbox prototype
+    Object.defineProperties(this._proto, {
+      module: { enumerable: true, value: module },
+      exports: { enumerable: true, value: module.exports },
+      console: {
+        enumerable: true,
+        value: Cu.cloneInto(directorScriptConsole, this._sandbox, { cloneFunctions: true })
+      }
+    });
+
+    Object.defineProperties(this._sandbox, {
+      require: {
+        enumerable: true,
+        value: Cu.cloneInto(function () {
+          throw Error("NOT IMPLEMENTED");
+        }, this._sandbox, { cloneFunctions: true })
+      }
+    });
+
+    // TODO: if the debugger target is local, the debugger client could pass
+    // to the director actor the resource url instead of the entire javascript source code.
+
+    // evaluate the director script source in the sandbox
+    evaluate(this._sandbox, this._scriptCode, "javascript:" + this._scriptCode);
+
+    // prepare the messageport connected to the debugger client
+    let { port1, port2 } = new this._window.MessageChannel();
+
+    // prepare the unload callbacks queue
+    var sandboxOnUnloadQueue = this._sandboxOnUnloadQueue = [];
+
+    // create the attach options
+    var attachOptions = this._attachOptions = Cu.createObjectIn(this._sandbox);
+    Object.defineProperties(attachOptions, {
+      port: { enumerable: true, value: port1 },
+      window: { enumerable: true, value: window },
+      scriptOptions: { enumerable: true, value: Cu.cloneInto(this._scriptOptions, this._sandbox) },
+      onUnload: {
+        enumerable: true,
+        value: Cu.cloneInto(function (cb) {
+          // collect unload callbacks
+          if (typeof cb == "function") {
+            sandboxOnUnloadQueue.push(cb);
+          }
+        }, this._sandbox, { cloneFunctions: true })
+      }
+    });
+
+    // select the attach method
+    var exports = this._proto.module.exports;
+    if (this._scriptOptions && "attachMethod" in this._scriptOptions) {
+      this._sandboxOnAttach = exports[this._scriptOptions.attachMethod];
+    } else {
+      this._sandboxOnAttach = exports;
+    }
+
+    if (typeof this._sandboxOnAttach !== "function") {
+      throw Error("the configured attachMethod '" +
+                  (this._scriptOptions.attachMethod || "module.exports") +
+                  "' is not exported by the directorScript");
+    }
+
+    // call the attach method
+    this._sandboxOnAttach.call(this._sandbox, attachOptions);
+
+    return port2;
+  },
+  destroy:  function (onError) {
+    // evaluate queue unload methods if any
+    while (this._sandboxOnUnloadQueue && this._sandboxOnUnloadQueue.length > 0) {
+      let cb = this._sandboxOnUnloadQueue.pop();
+
+      try {
+        cb();
+      } catch (e) {
+        console.error("Exception on DirectorScript Sandbox destroy", e);
+        onError(e);
+      }
+    }
+
+    Cu.nukeSandbox(this._sandbox);
+  }
+});
+
+function getWindowID(window) {
+  return window.QueryInterface(Ci.nsIInterfaceRequestor)
+               .getInterface(Ci.nsIDOMWindowUtils)
+               .currentInnerWindowID;
+}
diff --git a/devtools/server/actors/director-registry.js b/devtools/server/actors/director-registry.js
new file mode 100644
index 000000000..54584bcde
--- /dev/null
+++ b/devtools/server/actors/director-registry.js
@@ -0,0 +1,254 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const protocol = require("devtools/shared/protocol");
+
+const {DebuggerServer} = require("devtools/server/main");
+
+const {directorRegistrySpec} = require("devtools/shared/specs/director-registry");
+
+/**
+ * Error Messages
+ */
+
+const ERR_DIRECTOR_INSTALL_TWICE = "Trying to install a director-script twice";
+const ERR_DIRECTOR_INSTALL_EMPTY = "Trying to install an empty director-script";
+const ERR_DIRECTOR_UNINSTALL_UNKNOWN = "Trying to uninstall an unkown director-script";
+
+const ERR_DIRECTOR_PARENT_UNKNOWN_METHOD = "Unknown parent process method";
+const ERR_DIRECTOR_CHILD_NOTIMPLEMENTED_METHOD = "Unexpected call to notImplemented method";
+const ERR_DIRECTOR_CHILD_MULTIPLE_REPLIES = "Unexpected multiple replies to called parent method";
+const ERR_DIRECTOR_CHILD_NO_REPLY = "Unexpected no reply to called parent method";
+
+/**
+ * Director Registry
+ */
+
+// Map of director scripts ids to director script definitions
+var gDirectorScripts = Object.create(null);
+
+const DirectorRegistry = exports.DirectorRegistry = {
+  /**
+   * Register a Director Script with the debugger server.
+   * @param id string
+   *    The ID of a director script.
+   * @param directorScriptDef object
+   *    The definition of a director script.
+   */
+  install: function (id, scriptDef) {
+    if (id in gDirectorScripts) {
+      console.error(ERR_DIRECTOR_INSTALL_TWICE, id);
+      return false;
+    }
+
+    if (!scriptDef) {
+      console.error(ERR_DIRECTOR_INSTALL_EMPTY, id);
+      return false;
+    }
+
+    gDirectorScripts[id] = scriptDef;
+
+    return true;
+  },
+
+  /**
+   * Unregister a Director Script with the debugger server.
+   * @param id string
+   *    The ID of a director script.
+   */
+  uninstall: function (id) {
+    if (id in gDirectorScripts) {
+      delete gDirectorScripts[id];
+
+      return true;
+    }
+
+    console.error(ERR_DIRECTOR_UNINSTALL_UNKNOWN, id);
+
+    return false;
+  },
+
+  /**
+   * Returns true if a director script id has been registered.
+   * @param id string
+   *    The ID of a director script.
+   */
+  checkInstalled: function (id) {
+    return (this.list().indexOf(id) >= 0);
+  },
+
+  /**
+   * Returns a registered director script definition by id.
+   * @param id string
+   *    The ID of a director script.
+   */
+  get: function (id) {
+    return gDirectorScripts[id];
+  },
+
+  /**
+   * Returns an array of registered director script ids.
+   */
+  list: function () {
+    return Object.keys(gDirectorScripts);
+  },
+
+  /**
+   * Removes all the registered director scripts.
+   */
+  clear: function () {
+    gDirectorScripts = Object.create(null);
+  }
+};
+
+/**
+ * E10S parent/child setup helpers
+ */
+
+exports.setupParentProcess = function setupParentProcess({ mm, prefix }) {
+  // listen for director-script requests from the child process
+  setMessageManager(mm);
+
+  /* parent process helpers */
+
+  function handleChildRequest(msg) {
+    switch (msg.json.method) {
+      case "get":
+        return DirectorRegistry.get(msg.json.args[0]);
+      case "list":
+        return DirectorRegistry.list();
+      default:
+        console.error(ERR_DIRECTOR_PARENT_UNKNOWN_METHOD, msg.json.method);
+        throw new Error(ERR_DIRECTOR_PARENT_UNKNOWN_METHOD);
+    }
+  }
+
+  function setMessageManager(newMM) {
+    if (mm) {
+      mm.removeMessageListener("debug:director-registry-request", handleChildRequest);
+    }
+    mm = newMM;
+    if (mm) {
+      mm.addMessageListener("debug:director-registry-request", handleChildRequest);
+    }
+  }
+
+  return {
+    onBrowserSwap: setMessageManager,
+    onDisconnected: () => setMessageManager(null),
+  };
+};
+
+/**
+ * The DirectorRegistry Actor is a global actor which manages install/uninstall of
+ * director scripts definitions.
+ */
+const DirectorRegistryActor = exports.DirectorRegistryActor = protocol.ActorClassWithSpec(directorRegistrySpec, {
+  /* init & destroy methods */
+  initialize: function (conn, parentActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.maybeSetupChildProcess(conn);
+  },
+  destroy: function (conn) {
+    protocol.Actor.prototype.destroy.call(this, conn);
+    this.finalize();
+  },
+
+  finalize: function () {
+    // nothing to cleanup
+  },
+
+  maybeSetupChildProcess(conn) {
+    // skip child setup if this actor module is not running in a child process
+    if (!DebuggerServer.isInChildProcess) {
+      return;
+    }
+
+    const { sendSyncMessage } = conn.parentMessageManager;
+
+    conn.setupInParent({
+      module: "devtools/server/actors/director-registry",
+      setupParent: "setupParentProcess"
+    });
+
+    DirectorRegistry.install = notImplemented.bind(null, "install");
+    DirectorRegistry.uninstall = notImplemented.bind(null, "uninstall");
+    DirectorRegistry.clear = notImplemented.bind(null, "clear");
+
+    DirectorRegistry.get = callParentProcess.bind(null, "get");
+    DirectorRegistry.list = callParentProcess.bind(null, "list");
+
+    /* child process helpers */
+
+    function notImplemented(method) {
+      console.error(ERR_DIRECTOR_CHILD_NOTIMPLEMENTED_METHOD, method);
+      throw Error(ERR_DIRECTOR_CHILD_NOTIMPLEMENTED_METHOD);
+    }
+
+    function callParentProcess(method, ...args) {
+      var reply = sendSyncMessage("debug:director-registry-request", {
+        method: method,
+        args: args
+      });
+
+      if (reply.length === 0) {
+        console.error(ERR_DIRECTOR_CHILD_NO_REPLY);
+        throw Error(ERR_DIRECTOR_CHILD_NO_REPLY);
+      } else if (reply.length > 1) {
+        console.error(ERR_DIRECTOR_CHILD_MULTIPLE_REPLIES);
+        throw Error(ERR_DIRECTOR_CHILD_MULTIPLE_REPLIES);
+      }
+
+      return reply[0];
+    }
+  },
+
+  /**
+   * Install a new director-script definition.
+   *
+   * @param String id
+   *        The director-script definition identifier.
+   * @param String scriptCode
+   *        The director-script javascript source.
+   * @param Object scriptOptions
+   *        The director-script option object.
+   */
+  install: function (id, { scriptCode, scriptOptions }) {
+    // TODO: add more checks on id format?
+    if (!id || id.length === 0) {
+      throw Error("director-script id is mandatory");
+    }
+
+    if (!scriptCode) {
+      throw Error("director-script scriptCode is mandatory");
+    }
+
+    return DirectorRegistry.install(id, {
+      scriptId: id,
+      scriptCode: scriptCode,
+      scriptOptions: scriptOptions
+    });
+  },
+
+  /**
+   * Uninstall a director-script definition.
+   *
+   * @param String id
+   *        The identifier of the director-script definition to be removed
+   */
+  uninstall: function (id) {
+    return DirectorRegistry.uninstall(id);
+  },
+
+  /**
+   * Retrieves the list of installed director-scripts.
+   */
+  list: function () {
+    return DirectorRegistry.list();
+  }
+});
diff --git a/devtools/server/actors/emulation.js b/devtools/server/actors/emulation.js
new file mode 100644
index 000000000..b69183305
--- /dev/null
+++ b/devtools/server/actors/emulation.js
@@ -0,0 +1,241 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Ci } = require("chrome");
+const protocol = require("devtools/shared/protocol");
+const { emulationSpec } = require("devtools/shared/specs/emulation");
+const { SimulatorCore } = require("devtools/shared/touch/simulator-core");
+
+/**
+ * This actor overrides various browser features to simulate different environments to
+ * test how pages perform under various conditions.
+ *
+ * The design below, which saves the previous value of each property before setting, is
+ * needed because it's possible to have multiple copies of this actor for a single page.
+ * When some instance of this actor changes a property, we want it to be able to restore
+ * that property to the way it was found before the change.
+ *
+ * A subtle aspect of the code below is that all get* methods must return non-undefined
+ * values, so that the absence of a previous value can be distinguished from the value for
+ * "no override" for each of the properties.
+ */
+let EmulationActor = protocol.ActorClassWithSpec(emulationSpec, {
+
+  initialize(conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.tabActor = tabActor;
+    this.docShell = tabActor.docShell;
+    this.simulatorCore = new SimulatorCore(tabActor.chromeEventHandler);
+  },
+
+  disconnect() {
+    this.destroy();
+  },
+
+  destroy() {
+    this.clearDPPXOverride();
+    this.clearNetworkThrottling();
+    this.clearTouchEventsOverride();
+    this.clearUserAgentOverride();
+    this.tabActor = null;
+    this.docShell = null;
+    this.simulatorCore = null;
+    protocol.Actor.prototype.destroy.call(this);
+  },
+
+  /**
+   * Retrieve the console actor for this tab.  This allows us to expose network throttling
+   * as part of emulation settings, even though it's internally connected to the network
+   * monitor, which for historical reasons is part of the console actor.
+   */
+  get _consoleActor() {
+    if (this.tabActor.exited) {
+      return null;
+    }
+    let form = this.tabActor.form();
+    return this.conn._getOrCreateActor(form.consoleActor);
+  },
+
+  /* DPPX override */
+
+  _previousDPPXOverride: undefined,
+
+  setDPPXOverride(dppx) {
+    if (this.getDPPXOverride() === dppx) {
+      return false;
+    }
+
+    if (this._previousDPPXOverride === undefined) {
+      this._previousDPPXOverride = this.getDPPXOverride();
+    }
+
+    this.docShell.contentViewer.overrideDPPX = dppx;
+
+    return true;
+  },
+
+  getDPPXOverride() {
+    return this.docShell.contentViewer.overrideDPPX;
+  },
+
+  clearDPPXOverride() {
+    if (this._previousDPPXOverride !== undefined) {
+      return this.setDPPXOverride(this._previousDPPXOverride);
+    }
+
+    return false;
+  },
+
+  /* Network Throttling */
+
+  _previousNetworkThrottling: undefined,
+
+  /**
+   * Transform the RDP format into the internal format and then set network throttling.
+   */
+  setNetworkThrottling({ downloadThroughput, uploadThroughput, latency }) {
+    let throttleData = {
+      roundTripTimeMean: latency,
+      roundTripTimeMax: latency,
+      downloadBPSMean: downloadThroughput,
+      downloadBPSMax: downloadThroughput,
+      uploadBPSMean: uploadThroughput,
+      uploadBPSMax: uploadThroughput,
+    };
+    return this._setNetworkThrottling(throttleData);
+  },
+
+  _setNetworkThrottling(throttleData) {
+    let current = this._getNetworkThrottling();
+    // Check if they are both objects or both null
+    let match = throttleData == current;
+    // If both objects, check all entries
+    if (match && current && throttleData) {
+      match = Object.entries(current).every(([ k, v ]) => {
+        return throttleData[k] === v;
+      });
+    }
+    if (match) {
+      return false;
+    }
+
+    if (this._previousNetworkThrottling === undefined) {
+      this._previousNetworkThrottling = current;
+    }
+
+    let consoleActor = this._consoleActor;
+    if (!consoleActor) {
+      return false;
+    }
+    consoleActor.onStartListeners({
+      listeners: [ "NetworkActivity" ],
+    });
+    consoleActor.onSetPreferences({
+      preferences: {
+        "NetworkMonitor.throttleData": throttleData,
+      }
+    });
+    return true;
+  },
+
+  /**
+   * Get network throttling and then transform the internal format into the RDP format.
+   */
+  getNetworkThrottling() {
+    let throttleData = this._getNetworkThrottling();
+    if (!throttleData) {
+      return null;
+    }
+    let { downloadBPSMax, uploadBPSMax, roundTripTimeMax } = throttleData;
+    return {
+      downloadThroughput: downloadBPSMax,
+      uploadThroughput: uploadBPSMax,
+      latency: roundTripTimeMax,
+    };
+  },
+
+  _getNetworkThrottling() {
+    let consoleActor = this._consoleActor;
+    if (!consoleActor) {
+      return null;
+    }
+    let prefs = consoleActor.onGetPreferences({
+      preferences: [ "NetworkMonitor.throttleData" ],
+    });
+    return prefs.preferences["NetworkMonitor.throttleData"] || null;
+  },
+
+  clearNetworkThrottling() {
+    if (this._previousNetworkThrottling !== undefined) {
+      return this._setNetworkThrottling(this._previousNetworkThrottling);
+    }
+
+    return false;
+  },
+
+  /* Touch events override */
+
+  _previousTouchEventsOverride: undefined,
+
+  setTouchEventsOverride(flag) {
+    if (this.getTouchEventsOverride() == flag) {
+      return false;
+    }
+    if (this._previousTouchEventsOverride === undefined) {
+      this._previousTouchEventsOverride = this.getTouchEventsOverride();
+    }
+
+    // Start or stop the touch simulator depending on the override flag
+    if (flag == Ci.nsIDocShell.TOUCHEVENTS_OVERRIDE_ENABLED) {
+      this.simulatorCore.start();
+    } else {
+      this.simulatorCore.stop();
+    }
+
+    this.docShell.touchEventsOverride = flag;
+    return true;
+  },
+
+  getTouchEventsOverride() {
+    return this.docShell.touchEventsOverride;
+  },
+
+  clearTouchEventsOverride() {
+    if (this._previousTouchEventsOverride !== undefined) {
+      return this.setTouchEventsOverride(this._previousTouchEventsOverride);
+    }
+    return false;
+  },
+
+  /* User agent override */
+
+  _previousUserAgentOverride: undefined,
+
+  setUserAgentOverride(userAgent) {
+    if (this.getUserAgentOverride() == userAgent) {
+      return false;
+    }
+    if (this._previousUserAgentOverride === undefined) {
+      this._previousUserAgentOverride = this.getUserAgentOverride();
+    }
+    this.docShell.customUserAgent = userAgent;
+    return true;
+  },
+
+  getUserAgentOverride() {
+    return this.docShell.customUserAgent;
+  },
+
+  clearUserAgentOverride() {
+    if (this._previousUserAgentOverride !== undefined) {
+      return this.setUserAgentOverride(this._previousUserAgentOverride);
+    }
+    return false;
+  },
+
+});
+
+exports.EmulationActor = EmulationActor;
diff --git a/devtools/server/actors/environment.js b/devtools/server/actors/environment.js
new file mode 100644
index 000000000..bd03586eb
--- /dev/null
+++ b/devtools/server/actors/environment.js
@@ -0,0 +1,199 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const { ActorClassWithSpec } = require("devtools/shared/protocol");
+const { createValueGrip } = require("devtools/server/actors/object");
+const { environmentSpec } = require("devtools/shared/specs/environment");
+
+/**
+ * Creates an EnvironmentActor. EnvironmentActors are responsible for listing
+ * the bindings introduced by a lexical environment and assigning new values to
+ * those identifier bindings.
+ *
+ * @param Debugger.Environment aEnvironment
+ *        The lexical environment that will be used to create the actor.
+ * @param ThreadActor aThreadActor
+ *        The parent thread actor that contains this environment.
+ */
+let EnvironmentActor = ActorClassWithSpec(environmentSpec, {
+  initialize: function (environment, threadActor) {
+    this.obj = environment;
+    this.threadActor = threadActor;
+  },
+
+  /**
+   * Return an environment form for use in a protocol message.
+   */
+  form: function () {
+    let form = { actor: this.actorID };
+
+    // What is this environment's type?
+    if (this.obj.type == "declarative") {
+      form.type = this.obj.callee ? "function" : "block";
+    } else {
+      form.type = this.obj.type;
+    }
+
+    // Does this environment have a parent?
+    if (this.obj.parent) {
+      form.parent = (this.threadActor
+                     .createEnvironmentActor(this.obj.parent,
+                                             this.registeredPool)
+                     .form());
+    }
+
+    // Does this environment reflect the properties of an object as variables?
+    if (this.obj.type == "object" || this.obj.type == "with") {
+      form.object = createValueGrip(this.obj.object,
+        this.registeredPool, this.threadActor.objectGrip);
+    }
+
+    // Is this the environment created for a function call?
+    if (this.obj.callee) {
+      form.function = createValueGrip(this.obj.callee,
+        this.registeredPool, this.threadActor.objectGrip);
+    }
+
+    // Shall we list this environment's bindings?
+    if (this.obj.type == "declarative") {
+      form.bindings = this.bindings();
+    }
+
+    return form;
+  },
+
+  /**
+   * Handle a protocol request to change the value of a variable bound in this
+   * lexical environment.
+   *
+   * @param string name
+   *        The name of the variable to be changed.
+   * @param any value
+   *        The value to be assigned.
+   */
+  assign: function (name, value) {
+    // TODO: enable the commented-out part when getVariableDescriptor lands
+    // (bug 725815).
+    /* let desc = this.obj.getVariableDescriptor(name);
+
+    if (!desc.writable) {
+      return { error: "immutableBinding",
+               message: "Changing the value of an immutable binding is not " +
+                        "allowed" };
+    }*/
+
+    try {
+      this.obj.setVariable(name, value);
+    } catch (e) {
+      if (e instanceof Debugger.DebuggeeWouldRun) {
+        throw {
+          error: "threadWouldRun",
+          message: "Assigning a value would cause the debuggee to run"
+        };
+      } else {
+        throw e;
+      }
+    }
+    return { from: this.actorID };
+  },
+
+  /**
+   * Handle a protocol request to fully enumerate the bindings introduced by the
+   * lexical environment.
+   */
+  bindings: function () {
+    let bindings = { arguments: [], variables: {} };
+
+    // TODO: this part should be removed in favor of the commented-out part
+    // below when getVariableDescriptor lands (bug 725815).
+    if (typeof this.obj.getVariable != "function") {
+    // if (typeof this.obj.getVariableDescriptor != "function") {
+      return bindings;
+    }
+
+    let parameterNames;
+    if (this.obj.callee) {
+      parameterNames = this.obj.callee.parameterNames;
+    } else {
+      parameterNames = [];
+    }
+    for (let name of parameterNames) {
+      let arg = {};
+      let value = this.obj.getVariable(name);
+
+      // TODO: this part should be removed in favor of the commented-out part
+      // below when getVariableDescriptor lands (bug 725815).
+      let desc = {
+        value: value,
+        configurable: false,
+        writable: !(value && value.optimizedOut),
+        enumerable: true
+      };
+
+      // let desc = this.obj.getVariableDescriptor(name);
+      let descForm = {
+        enumerable: true,
+        configurable: desc.configurable
+      };
+      if ("value" in desc) {
+        descForm.value = createValueGrip(desc.value,
+          this.registeredPool, this.threadActor.objectGrip);
+        descForm.writable = desc.writable;
+      } else {
+        descForm.get = createValueGrip(desc.get, this.registeredPool,
+          this.threadActor.objectGrip);
+        descForm.set = createValueGrip(desc.set, this.registeredPool,
+          this.threadActor.objectGrip);
+      }
+      arg[name] = descForm;
+      bindings.arguments.push(arg);
+    }
+
+    for (let name of this.obj.names()) {
+      if (bindings.arguments.some(function exists(element) {
+        return !!element[name];
+      })) {
+        continue;
+      }
+
+      let value = this.obj.getVariable(name);
+
+      // TODO: this part should be removed in favor of the commented-out part
+      // below when getVariableDescriptor lands.
+      let desc = {
+        value: value,
+        configurable: false,
+        writable: !(value &&
+                    (value.optimizedOut ||
+                     value.uninitialized ||
+                     value.missingArguments)),
+        enumerable: true
+      };
+
+      // let desc = this.obj.getVariableDescriptor(name);
+      let descForm = {
+        enumerable: true,
+        configurable: desc.configurable
+      };
+      if ("value" in desc) {
+        descForm.value = createValueGrip(desc.value,
+          this.registeredPool, this.threadActor.objectGrip);
+        descForm.writable = desc.writable;
+      } else {
+        descForm.get = createValueGrip(desc.get || undefined,
+          this.registeredPool, this.threadActor.objectGrip);
+        descForm.set = createValueGrip(desc.set || undefined,
+          this.registeredPool, this.threadActor.objectGrip);
+      }
+      bindings.variables[name] = descForm;
+    }
+
+    return bindings;
+  }
+});
+
+exports.EnvironmentActor = EnvironmentActor;
diff --git a/devtools/server/actors/errordocs.js b/devtools/server/actors/errordocs.js
new file mode 100644
index 000000000..27f687dc7
--- /dev/null
+++ b/devtools/server/actors/errordocs.js
@@ -0,0 +1,84 @@
+/* this source code form is subject to the terms of the mozilla public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * A mapping of error message names to external documentation. Any error message
+ * included here will be displayed alongside its link in the web console.
+ */
+
+"use strict";
+
+const baseURL = "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Errors/";
+const params = "?utm_source=mozilla&utm_medium=firefox-console-errors&utm_campaign=default";
+const ErrorDocs = {
+  JSMSG_READ_ONLY: "Read-only",
+  JSMSG_BAD_ARRAY_LENGTH: "Invalid_array_length",
+  JSMSG_NEGATIVE_REPETITION_COUNT: "Negative_repetition_count",
+  JSMSG_RESULTING_STRING_TOO_LARGE: "Resulting_string_too_large",
+  JSMSG_BAD_RADIX: "Bad_radix",
+  JSMSG_PRECISION_RANGE: "Precision_range",
+  JSMSG_BAD_FORMAL: "Malformed_formal_parameter",
+  JSMSG_STMT_AFTER_RETURN: "Stmt_after_return",
+  JSMSG_NOT_A_CODEPOINT: "Not_a_codepoint",
+  JSMSG_BAD_SORT_ARG: "Array_sort_argument",
+  JSMSG_UNEXPECTED_TYPE: "Unexpected_type",
+  JSMSG_NOT_DEFINED: "Not_defined",
+  JSMSG_NOT_FUNCTION: "Not_a_function",
+  JSMSG_EQUAL_AS_ASSIGN: "Equal_as_assign",
+  JSMSG_UNDEFINED_PROP: "Undefined_prop",
+  JSMSG_DEPRECATED_PRAGMA: "Deprecated_source_map_pragma",
+  JSMSG_DEPRECATED_USAGE: "Deprecated_caller_or_arguments_usage",
+  JSMSG_CANT_DELETE: "Cant_delete",
+  JSMSG_VAR_HIDES_ARG: "Var_hides_argument",
+  JSMSG_JSON_BAD_PARSE: "JSON_bad_parse",
+  JSMSG_UNDECLARED_VAR: "Undeclared_var",
+  JSMSG_UNEXPECTED_TOKEN: "Unexpected_token",
+  JSMSG_BAD_OCTAL: "Bad_octal",
+  JSMSG_PROPERTY_ACCESS_DENIED: "Property_access_denied",
+  JSMSG_NO_PROPERTIES: "No_properties",
+  JSMSG_ALREADY_HAS_PRAGMA: "Already_has_pragma",
+  JSMSG_BAD_RETURN_OR_YIELD: "Bad_return_or_yield",
+  JSMSG_SEMI_BEFORE_STMNT: "Missing_semicolon_before_statement",
+  JSMSG_OVER_RECURSED: "Too_much_recursion",
+  JSMSG_BRACKET_AFTER_LIST: "Missing_bracket_after_list",
+  JSMSG_PAREN_AFTER_ARGS: "Missing_parenthesis_after_argument_list",
+  JSMSG_MORE_ARGS_NEEDED: "More_arguments_needed",
+  JSMSG_BAD_LEFTSIDE_OF_ASS: "Invalid_assignment_left-hand_side",
+  JSMSG_UNTERMINATED_STRING: "Unterminated_string_literal",
+  JSMSG_NOT_CONSTRUCTOR: "Not_a_constructor",
+  JSMSG_CURLY_AFTER_LIST: "Missing_curly_after_property_list",
+  JSMSG_DEPRECATED_FOR_EACH: "For-each-in_loops_are_deprecated",
+};
+
+const MIXED_CONTENT_LEARN_MORE = "https://developer.mozilla.org/docs/Web/Security/Mixed_content";
+const TRACKING_PROTECTION_LEARN_MORE = "https://developer.mozilla.org/Firefox/Privacy/Tracking_Protection";
+const INSECURE_PASSWORDS_LEARN_MORE = "https://developer.mozilla.org/docs/Web/Security/Insecure_passwords";
+const PUBLIC_KEY_PINS_LEARN_MORE = "https://developer.mozilla.org/docs/Web/Security/Public_Key_Pinning";
+const STRICT_TRANSPORT_SECURITY_LEARN_MORE = "https://developer.mozilla.org/docs/Web/Security/HTTP_strict_transport_security";
+const WEAK_SIGNATURE_ALGORITHM_LEARN_MORE = "https://developer.mozilla.org/docs/Web/Security/Weak_Signature_Algorithm";
+const ErrorCategories = {
+  "Insecure Password Field": INSECURE_PASSWORDS_LEARN_MORE,
+  "Mixed Content Message": MIXED_CONTENT_LEARN_MORE,
+  "Mixed Content Blocker": MIXED_CONTENT_LEARN_MORE,
+  "Invalid HPKP Headers": PUBLIC_KEY_PINS_LEARN_MORE,
+  "Invalid HSTS Headers": STRICT_TRANSPORT_SECURITY_LEARN_MORE,
+  "SHA-1 Signature": WEAK_SIGNATURE_ALGORITHM_LEARN_MORE,
+  "Tracking Protection": TRACKING_PROTECTION_LEARN_MORE,
+};
+
+exports.GetURL = (error) => {
+  if (!error) {
+    return;
+  }
+
+  let doc = ErrorDocs[error.errorMessageName];
+  if (doc) {
+    return baseURL + doc + params;
+  }
+
+  let categoryURL = ErrorCategories[error.category];
+  if (categoryURL) {
+    return categoryURL + params;
+  }
+};
diff --git a/devtools/server/actors/eventlooplag.js b/devtools/server/actors/eventlooplag.js
new file mode 100644
index 000000000..6e0a101c9
--- /dev/null
+++ b/devtools/server/actors/eventlooplag.js
@@ -0,0 +1,60 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * The eventLoopLag actor emits "event-loop-lag" events when the event
+ * loop gets unresponsive. The event comes with a "time" property (the
+ * duration of the lag in milliseconds).
+ */
+
+const {Ci} = require("chrome");
+const Services = require("Services");
+const {XPCOMUtils} = require("resource://gre/modules/XPCOMUtils.jsm");
+const {Actor, ActorClassWithSpec} = require("devtools/shared/protocol");
+const events = require("sdk/event/core");
+const {eventLoopLagSpec} = require("devtools/shared/specs/eventlooplag");
+
+var EventLoopLagActor = exports.EventLoopLagActor = ActorClassWithSpec(eventLoopLagSpec, {
+  _observerAdded: false,
+
+  /**
+   * Start tracking the event loop lags.
+   */
+  start: function () {
+    if (!this._observerAdded) {
+      Services.obs.addObserver(this, "event-loop-lag", false);
+      this._observerAdded = true;
+    }
+    return Services.appShell.startEventLoopLagTracking();
+  },
+
+  /**
+   * Stop tracking the event loop lags.
+   */
+  stop: function () {
+    if (this._observerAdded) {
+      Services.obs.removeObserver(this, "event-loop-lag");
+      this._observerAdded = false;
+    }
+    Services.appShell.stopEventLoopLagTracking();
+  },
+
+  destroy: function () {
+    this.stop();
+    Actor.prototype.destroy.call(this);
+  },
+
+  // nsIObserver
+
+  observe: function (subject, topic, data) {
+    if (topic == "event-loop-lag") {
+      // Forward event loop lag event
+      events.emit(this, "event-loop-lag", data);
+    }
+  },
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver]),
+});
diff --git a/devtools/server/actors/frame.js b/devtools/server/actors/frame.js
new file mode 100644
index 000000000..fefcad1b0
--- /dev/null
+++ b/devtools/server/actors/frame.js
@@ -0,0 +1,100 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { ActorPool } = require("devtools/server/actors/common");
+const { createValueGrip } = require("devtools/server/actors/object");
+const { ActorClassWithSpec } = require("devtools/shared/protocol");
+const { frameSpec } = require("devtools/shared/specs/frame");
+
+/**
+ * An actor for a specified stack frame.
+ */
+let FrameActor = ActorClassWithSpec(frameSpec, {
+  /**
+   * Creates the Frame actor.
+   *
+   * @param frame Debugger.Frame
+   *        The debuggee frame.
+   * @param threadActor ThreadActor
+   *        The parent thread actor for this frame.
+   */
+  initialize: function (frame, threadActor) {
+    this.frame = frame;
+    this.threadActor = threadActor;
+  },
+
+  /**
+   * A pool that contains frame-lifetime objects, like the environment.
+   */
+  _frameLifetimePool: null,
+  get frameLifetimePool() {
+    if (!this._frameLifetimePool) {
+      this._frameLifetimePool = new ActorPool(this.conn);
+      this.conn.addActorPool(this._frameLifetimePool);
+    }
+    return this._frameLifetimePool;
+  },
+
+  /**
+   * Finalization handler that is called when the actor is being evicted from
+   * the pool.
+   */
+  disconnect: function () {
+    this.conn.removeActorPool(this._frameLifetimePool);
+    this._frameLifetimePool = null;
+  },
+
+  /**
+   * Returns a frame form for use in a protocol message.
+   */
+  form: function () {
+    let threadActor = this.threadActor;
+    let form = { actor: this.actorID,
+                 type: this.frame.type };
+    if (this.frame.type === "call") {
+      form.callee = createValueGrip(this.frame.callee, threadActor._pausePool,
+        threadActor.objectGrip);
+    }
+
+    if (this.frame.environment) {
+      let envActor = threadActor.createEnvironmentActor(
+        this.frame.environment,
+        this.frameLifetimePool
+      );
+      form.environment = envActor.form();
+    }
+    form.this = createValueGrip(this.frame.this, threadActor._pausePool,
+      threadActor.objectGrip);
+    form.arguments = this._args();
+    if (this.frame.script) {
+      var generatedLocation = this.threadActor.sources.getFrameLocation(this.frame);
+      form.where = {
+        source: generatedLocation.generatedSourceActor.form(),
+        line: generatedLocation.generatedLine,
+        column: generatedLocation.generatedColumn
+      };
+    }
+
+    if (!this.frame.older) {
+      form.oldest = true;
+    }
+
+    return form;
+  },
+
+  _args: function () {
+    if (!this.frame.arguments) {
+      return [];
+    }
+
+    return this.frame.arguments.map(arg => createValueGrip(arg,
+      this.threadActor._pausePool, this.threadActor.objectGrip));
+  }
+});
+
+exports.FrameActor = FrameActor;
diff --git a/devtools/server/actors/framerate.js b/devtools/server/actors/framerate.js
new file mode 100644
index 000000000..872cd7360
--- /dev/null
+++ b/devtools/server/actors/framerate.js
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const { Actor, ActorClassWithSpec } = require("devtools/shared/protocol");
+const { actorBridgeWithSpec } = require("devtools/server/actors/common");
+const { on, once, off, emit } = require("sdk/event/core");
+const { Framerate } = require("devtools/server/performance/framerate");
+const { framerateSpec } = require("devtools/shared/specs/framerate");
+
+/**
+ * An actor wrapper around Framerate. Uses exposed
+ * methods via bridge and provides RDP definitions.
+ *
+ * @see devtools/server/performance/framerate.js for documentation.
+ */
+var FramerateActor = exports.FramerateActor = ActorClassWithSpec(framerateSpec, {
+  initialize: function (conn, tabActor) {
+    Actor.prototype.initialize.call(this, conn);
+    this.bridge = new Framerate(tabActor);
+  },
+  destroy: function (conn) {
+    Actor.prototype.destroy.call(this, conn);
+    this.bridge.destroy();
+  },
+
+  startRecording: actorBridgeWithSpec("startRecording"),
+  stopRecording: actorBridgeWithSpec("stopRecording"),
+  cancelRecording: actorBridgeWithSpec("cancelRecording"),
+  isRecording: actorBridgeWithSpec("isRecording"),
+  getPendingTicks: actorBridgeWithSpec("getPendingTicks"),
+});
diff --git a/devtools/server/actors/gcli.js b/devtools/server/actors/gcli.js
new file mode 100644
index 000000000..651825a28
--- /dev/null
+++ b/devtools/server/actors/gcli.js
@@ -0,0 +1,233 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Task } = require("devtools/shared/task");
+const {
+  method, Arg, Option, RetVal, Actor, ActorClassWithSpec
+} = require("devtools/shared/protocol");
+const { gcliSpec } = require("devtools/shared/specs/gcli");
+const events = require("sdk/event/core");
+const { createSystem } = require("gcli/system");
+
+/**
+ * Manage remote connections that want to talk to GCLI
+ */
+const GcliActor = ActorClassWithSpec(gcliSpec, {
+  initialize: function (conn, tabActor) {
+    Actor.prototype.initialize.call(this, conn);
+
+    this._commandsChanged = this._commandsChanged.bind(this);
+
+    this._tabActor = tabActor;
+    this._requisitionPromise = undefined; // see _getRequisition()
+  },
+
+  disconnect: function () {
+    return this.destroy();
+  },
+
+  destroy: function () {
+    Actor.prototype.destroy.call(this);
+
+    // If _getRequisition has not been called, just bail quickly
+    if (this._requisitionPromise == null) {
+      this._commandsChanged = undefined;
+      this._tabActor = undefined;
+      return Promise.resolve();
+    }
+
+    return this._getRequisition().then(requisition => {
+      requisition.destroy();
+
+      this._system.commands.onCommandsChange.remove(this._commandsChanged);
+      this._system.destroy();
+      this._system = undefined;
+
+      this._requisitionPromise = undefined;
+      this._tabActor = undefined;
+
+      this._commandsChanged = undefined;
+    });
+  },
+
+  /**
+   * Load a module into the requisition
+   */
+  _testOnlyAddItemsByModule: function (names) {
+    return this._getRequisition().then(requisition => {
+      return requisition.system.addItemsByModule(names);
+    });
+  },
+
+  /**
+   * Unload a module from the requisition
+   */
+  _testOnlyRemoveItemsByModule: function (names) {
+    return this._getRequisition().then(requisition => {
+      return requisition.system.removeItemsByModule(names);
+    });
+  },
+
+  /**
+   * Retrieve a list of the remotely executable commands
+   * @param customProps Array of strings containing additional properties which,
+   * if specified in the command spec, will be included in the JSON. Normally we
+   * transfer only the properties required for GCLI to function.
+   */
+  specs: function (customProps) {
+    return this._getRequisition().then(requisition => {
+      return requisition.system.commands.getCommandSpecs(customProps);
+    });
+  },
+
+  /**
+   * Execute a GCLI command
+   * @return a promise of an object with the following properties:
+   * - data: The output of the command
+   * - type: The type of the data to allow selection of a converter
+   * - error: True if the output was considered an error
+   */
+  execute: function (typed) {
+    return this._getRequisition().then(requisition => {
+      return requisition.updateExec(typed).then(output => output.toJson());
+    });
+  },
+
+  /**
+   * Get the state of an input string. i.e. requisition.getStateData()
+   */
+  state: function (typed, start, rank) {
+    return this._getRequisition().then(requisition => {
+      return requisition.update(typed).then(() => {
+        return requisition.getStateData(start, rank);
+      });
+    });
+  },
+
+  /**
+   * Call type.parse to check validity. Used by the remote type
+   * @return a promise of an object with the following properties:
+   * - status: Of of the following strings: VALID|INCOMPLETE|ERROR
+   * - message: The message to display to the user
+   * - predictions: An array of suggested values for the given parameter
+   */
+  parseType: function (typed, paramName) {
+    return this._getRequisition().then(requisition => {
+      return requisition.update(typed).then(() => {
+        let assignment = requisition.getAssignment(paramName);
+        return Promise.resolve(assignment.predictions).then(predictions => {
+          return {
+            status: assignment.getStatus().toString(),
+            message: assignment.message,
+            predictions: predictions
+          };
+        });
+      });
+    });
+  },
+
+  /**
+   * Get the incremented/decremented value of some type
+   * @return a promise of a string containing the new argument text
+   */
+  nudgeType: function (typed, by, paramName) {
+    return this.requisition.update(typed).then(() => {
+      const assignment = this.requisition.getAssignment(paramName);
+      return this.requisition.nudge(assignment, by).then(() => {
+        return assignment.arg == null ? undefined : assignment.arg.text;
+      });
+    });
+  },
+
+  /**
+   * Perform a lookup on a selection type to get the allowed values
+   */
+  getSelectionLookup: function (commandName, paramName) {
+    return this._getRequisition().then(requisition => {
+      const command = requisition.system.commands.get(commandName);
+      if (command == null) {
+        throw new Error("No command called '" + commandName + "'");
+      }
+
+      let type;
+      command.params.forEach(param => {
+        if (param.name === paramName) {
+          type = param.type;
+        }
+      });
+
+      if (type == null) {
+        throw new Error("No parameter called '" + paramName + "' in '" +
+                        commandName + "'");
+      }
+
+      const reply = type.getLookup(requisition.executionContext);
+      return Promise.resolve(reply).then(lookup => {
+        // lookup returns an array of objects with name/value properties and
+        // the values might not be JSONable, so remove them
+        return lookup.map(info => ({ name: info.name }));
+      });
+    });
+  },
+
+  /**
+   * Lazy init for a Requisition
+   */
+  _getRequisition: function () {
+    if (this._tabActor == null) {
+      throw new Error("GcliActor used post-destroy");
+    }
+
+    if (this._requisitionPromise != null) {
+      return this._requisitionPromise;
+    }
+
+    const Requisition = require("gcli/cli").Requisition;
+    const tabActor = this._tabActor;
+
+    this._system = createSystem({ location: "server" });
+    this._system.commands.onCommandsChange.add(this._commandsChanged);
+
+    const gcliInit = require("devtools/shared/gcli/commands/index");
+    gcliInit.addAllItemsByModule(this._system);
+
+    // this._requisitionPromise should be created synchronously with the call
+    // to _getRequisition so that destroy can tell whether there is an async
+    // init in progress
+    this._requisitionPromise = this._system.load().then(() => {
+      const environment = {
+        get chromeWindow() {
+          throw new Error("environment.chromeWindow is not available in runAt:server commands");
+        },
+
+        get chromeDocument() {
+          throw new Error("environment.chromeDocument is not available in runAt:server commands");
+        },
+
+        get window() {
+          return tabActor.window;
+        },
+
+        get document() {
+          return tabActor.window && tabActor.window.document;
+        }
+      };
+
+      return new Requisition(this._system, { environment: environment });
+    });
+
+    return this._requisitionPromise;
+  },
+
+  /**
+   * Pass events from requisition.system.commands.onCommandsChange upwards
+   */
+  _commandsChanged: function () {
+    events.emit(this, "commands-changed");
+  },
+});
+
+exports.GcliActor = GcliActor;
diff --git a/devtools/server/actors/heap-snapshot-file.js b/devtools/server/actors/heap-snapshot-file.js
new file mode 100644
index 000000000..545f2265d
--- /dev/null
+++ b/devtools/server/actors/heap-snapshot-file.js
@@ -0,0 +1,68 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const protocol = require("devtools/shared/protocol");
+const { method, Arg } = protocol;
+const Services = require("Services");
+const { Task } = require("devtools/shared/task");
+
+const { heapSnapshotFileSpec } = require("devtools/shared/specs/heap-snapshot-file");
+
+loader.lazyRequireGetter(this, "DevToolsUtils",
+                         "devtools/shared/DevToolsUtils");
+loader.lazyRequireGetter(this, "OS", "resource://gre/modules/osfile.jsm", true);
+loader.lazyRequireGetter(this, "HeapSnapshotFileUtils",
+                         "devtools/shared/heapsnapshot/HeapSnapshotFileUtils");
+
+/**
+ * The HeapSnapshotFileActor handles transferring heap snapshot files from the
+ * server to the client. This has to be a global actor in the parent process
+ * because child processes are sandboxed and do not have access to the file
+ * system.
+ */
+exports.HeapSnapshotFileActor = protocol.ActorClassWithSpec(heapSnapshotFileSpec, {
+  initialize: function (conn, parent) {
+    if (Services.appinfo.processType !== Services.appinfo.PROCESS_TYPE_DEFAULT) {
+      const err = new Error("Attempt to create a HeapSnapshotFileActor in a " +
+                            "child process! The HeapSnapshotFileActor *MUST* " +
+                            "be in the parent process!");
+      DevToolsUtils.reportException(
+        "HeapSnapshotFileActor.prototype.initialize", err);
+      return;
+    }
+
+    protocol.Actor.prototype.initialize.call(this, conn, parent);
+  },
+
+  /**
+   * @see MemoryFront.prototype.transferHeapSnapshot
+   */
+  transferHeapSnapshot: Task.async(function* (snapshotId) {
+    const snapshotFilePath =
+          HeapSnapshotFileUtils.getHeapSnapshotTempFilePath(snapshotId);
+    if (!snapshotFilePath) {
+      throw new Error(`No heap snapshot with id: ${snapshotId}`);
+    }
+
+    const streamPromise = DevToolsUtils.openFileStream(snapshotFilePath);
+
+    const { size } = yield OS.File.stat(snapshotFilePath);
+    const bulkPromise = this.conn.startBulkSend({
+      actor: this.actorID,
+      type: "heap-snapshot",
+      length: size
+    });
+
+    const [bulk, stream] = yield Promise.all([bulkPromise, streamPromise]);
+
+    try {
+      yield bulk.copyFrom(stream);
+    } finally {
+      stream.close();
+    }
+  }),
+
+});
diff --git a/devtools/server/actors/highlighters.css b/devtools/server/actors/highlighters.css
new file mode 100644
index 000000000..87375ea36
--- /dev/null
+++ b/devtools/server/actors/highlighters.css
@@ -0,0 +1,536 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+  The :-moz-native-anonymous selector prefix prevents the styles defined here
+  from impacting web content. Indeed, this pseudo-class is only available to chrome code.
+  This stylesheet is loaded as a ua stylesheet via the addon sdk, so having this
+  pseudo-class is important.
+  Having bug 1086532 fixed would make it possible to load this stylesheet in a
+  <style scoped> node instead, directly in the native anonymous container
+  element.
+
+  A specific selector should still be specified to avoid impacting non-devtools
+  chrome content.
+*/
+
+:-moz-native-anonymous .highlighter-container {
+  /*
+  Content CSS applying to the html element impact the highlighters.
+  To avoid that, possible cases have been set to initial.
+  */
+  text-transform: initial;
+  text-indent: initial;
+  letter-spacing: initial;
+  word-spacing: initial;
+  color: initial;
+}
+
+:-moz-native-anonymous .highlighter-container {
+  --highlighter-guide-color: #08c;
+  --highlighter-content-color: #87ceeb;
+  --highlighter-bubble-text-color: hsl(216, 33%, 97%);
+  --highlighter-bubble-background-color: hsl(214, 13%, 24%);
+  --highlighter-bubble-border-color: rgba(255, 255, 255, 0.2);
+}
+
+:-moz-native-anonymous .highlighter-container {
+  position: fixed;
+  width: 100%;
+  height: 100%;
+  /* The container for all highlighters doesn't react to pointer-events by
+     default. This is because most highlighters cover the whole viewport but
+     don't contain UIs that need to be accessed.
+     If your highlighter has UI that needs to be interacted with, add
+     'pointer-events:auto;' on its container element. */
+  pointer-events: none;
+}
+
+:-moz-native-anonymous .highlighter-container.box-model {
+  /* Make the box-model container have a z-index other than auto so it always sits above
+     other highlighters. */
+  z-index: 1;
+}
+
+:-moz-native-anonymous .highlighter-container [hidden] {
+  display: none;
+}
+
+:-moz-native-anonymous .highlighter-container [dragging] {
+  cursor: grabbing;
+}
+
+/* Box Model Highlighter */
+
+:-moz-native-anonymous .box-model-regions {
+  opacity: 0.6;
+}
+
+/* Box model regions can be faded (see the onlyRegionArea option in
+   highlighters.js) in order to only display certain regions. */
+:-moz-native-anonymous .box-model-regions [faded] {
+  display: none;
+}
+
+:-moz-native-anonymous .box-model-content {
+  fill: var(--highlighter-content-color);
+}
+
+:-moz-native-anonymous .box-model-padding {
+  fill: #6a5acd;
+}
+
+:-moz-native-anonymous .box-model-border {
+  fill: #444444;
+}
+
+:-moz-native-anonymous .box-model-margin {
+  fill: #edff64;
+}
+
+:-moz-native-anonymous .box-model-content,
+:-moz-native-anonymous .box-model-padding,
+:-moz-native-anonymous .box-model-border,
+:-moz-native-anonymous .box-model-margin {
+  stroke: none;
+}
+
+:-moz-native-anonymous .box-model-guide-top,
+:-moz-native-anonymous .box-model-guide-right,
+:-moz-native-anonymous .box-model-guide-bottom,
+:-moz-native-anonymous .box-model-guide-left {
+  stroke: var(--highlighter-guide-color);
+  stroke-dasharray: 5 3;
+  shape-rendering: crispEdges;
+}
+
+/* Highlighter - Infobar */
+
+:-moz-native-anonymous [class$=infobar-container] {
+  position: absolute;
+  max-width: 95%;
+
+  font: message-box;
+  font-size: 11px;
+}
+
+:-moz-native-anonymous [class$=infobar] {
+  position: relative;
+
+  /* Centering the infobar in the container */
+  left: -50%;
+
+  padding: 5px;
+  min-width: 75px;
+
+  border-radius: 3px;
+  background: var(--highlighter-bubble-background-color) no-repeat padding-box;
+
+  color: var(--highlighter-bubble-text-color);
+  text-shadow: none;
+
+  border: 1px solid var(--highlighter-bubble-border-color);
+}
+
+:-moz-native-anonymous [class$=infobar-container][hide-arrow] > [class$=infobar] {
+  margin: 7px 0;
+}
+
+/* Arrows */
+
+:-moz-native-anonymous [class$=infobar-container] > [class$=infobar]:before {
+  left: calc(50% - 8px);
+  border: 8px solid var(--highlighter-bubble-border-color);
+}
+
+:-moz-native-anonymous [class$=infobar-container] > [class$=infobar]:after {
+  left: calc(50% - 7px);
+  border: 7px solid var(--highlighter-bubble-background-color);
+}
+
+:-moz-native-anonymous [class$=infobar-container] > [class$=infobar]:before,
+:-moz-native-anonymous [class$=infobar-container] > [class$=infobar]:after {
+  content: "";
+  display: none;
+  position: absolute;
+  height: 0;
+  width: 0;
+  border-left-color: transparent;
+  border-right-color: transparent;
+}
+
+:-moz-native-anonymous [class$=infobar-container][position="top"]:not([hide-arrow]) > [class$=infobar]:before,
+:-moz-native-anonymous [class$=infobar-container][position="top"]:not([hide-arrow]) > [class$=infobar]:after {
+  border-bottom: 0;
+  top: 100%;
+  display: block;
+}
+
+:-moz-native-anonymous [class$=infobar-container][position="bottom"]:not([hide-arrow]) > [class$=infobar]:before,
+:-moz-native-anonymous [class$=infobar-container][position="bottom"]:not([hide-arrow]) > [class$=infobar]:after {
+  border-top: 0;
+  bottom: 100%;
+  display: block;
+}
+
+/* Text Container */
+
+:-moz-native-anonymous [class$=infobar-text] {
+  overflow: hidden;
+  white-space: nowrap;
+  direction: ltr;
+  padding-bottom: 1px;
+  display: flex;
+}
+
+:-moz-native-anonymous .box-model-infobar-tagname {
+  color: hsl(285,100%, 75%);
+}
+
+:-moz-native-anonymous .box-model-infobar-id {
+  color: hsl(103, 46%, 54%);
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+:-moz-native-anonymous .box-model-infobar-classes,
+:-moz-native-anonymous .box-model-infobar-pseudo-classes {
+  color: hsl(200, 74%, 57%);
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+:-moz-native-anonymous [class$=infobar-dimensions] {
+  color: hsl(210, 30%, 85%);
+  border-inline-start: 1px solid #5a6169;
+  margin-inline-start: 6px;
+  padding-inline-start: 6px;
+}
+
+/* CSS Grid Highlighter */
+
+:-moz-native-anonymous .css-grid-canvas {
+  position: absolute;
+  pointer-events: none;
+  top: 0;
+  left: 0;
+  image-rendering: -moz-crisp-edges;
+}
+
+:-moz-native-anonymous .css-grid-regions {
+  opacity: 0.6;
+}
+
+:-moz-native-anonymous .css-grid-areas {
+  fill: #CEC0ED;
+  stroke: none;
+}
+
+:-moz-native-anonymous .css-grid-infobar-areaname {
+  color: hsl(285,100%, 75%);
+}
+
+/* CSS Transform Highlighter */
+
+:-moz-native-anonymous .css-transform-transformed {
+  fill: var(--highlighter-content-color);
+  opacity: 0.8;
+}
+
+:-moz-native-anonymous .css-transform-untransformed {
+  fill: #66cc52;
+  opacity: 0.8;
+}
+
+:-moz-native-anonymous .css-transform-transformed,
+:-moz-native-anonymous .css-transform-untransformed,
+:-moz-native-anonymous .css-transform-line {
+  stroke: var(--highlighter-guide-color);
+  stroke-dasharray: 5 3;
+  stroke-width: 2;
+}
+
+/* Rect Highlighter */
+
+:-moz-native-anonymous .highlighted-rect {
+  position: absolute;
+  background: var(--highlighter-content-color);
+  opacity: 0.8;
+}
+
+/* Element Geometry Highlighter */
+
+:-moz-native-anonymous .geometry-editor-root {
+  /* The geometry editor can be interacted with, so it needs to react to
+     pointer events */
+  pointer-events: auto;
+  -moz-user-select: none;
+}
+
+:-moz-native-anonymous .geometry-editor-offset-parent {
+  stroke: var(--highlighter-guide-color);
+  shape-rendering: crispEdges;
+  stroke-dasharray: 5 3;
+  fill: transparent;
+}
+
+:-moz-native-anonymous .geometry-editor-current-node {
+  stroke: var(--highlighter-guide-color);
+  fill: var(--highlighter-content-color);
+  shape-rendering: crispEdges;
+  opacity: 0.6;
+}
+
+:-moz-native-anonymous .geometry-editor-arrow {
+  stroke: var(--highlighter-guide-color);
+  shape-rendering: crispEdges;
+}
+
+:-moz-native-anonymous .geometry-editor-root circle {
+  stroke: var(--highlighter-guide-color);
+  fill: var(--highlighter-content-color);
+}
+
+:-moz-native-anonymous .geometry-editor-handler-top,
+:-moz-native-anonymous .geometry-editor-handler-bottom {
+  cursor: ns-resize;
+}
+
+:-moz-native-anonymous .geometry-editor-handler-right,
+:-moz-native-anonymous .geometry-editor-handler-left {
+  cursor: ew-resize;
+}
+
+:-moz-native-anonymous [dragging] .geometry-editor-handler-top,
+:-moz-native-anonymous [dragging] .geometry-editor-handler-right,
+:-moz-native-anonymous [dragging] .geometry-editor-handler-bottom,
+:-moz-native-anonymous [dragging] .geometry-editor-handler-left {
+  cursor: grabbing;
+}
+
+:-moz-native-anonymous .geometry-editor-handler-top.dragging,
+:-moz-native-anonymous .geometry-editor-handler-right.dragging,
+:-moz-native-anonymous .geometry-editor-handler-bottom.dragging,
+:-moz-native-anonymous .geometry-editor-handler-left.dragging {
+  fill: var(--highlighter-guide-color);
+}
+
+:-moz-native-anonymous .geometry-editor-label-bubble {
+  fill: var(--highlighter-bubble-background-color);
+  shape-rendering: crispEdges;
+}
+
+:-moz-native-anonymous .geometry-editor-label-text {
+  fill: var(--highlighter-bubble-text-color);
+  font: message-box;
+  font-size: 10px;
+  text-anchor: middle;
+  dominant-baseline: middle;
+}
+
+/* Rulers Highlighter */
+
+:-moz-native-anonymous .rulers-highlighter-elements {
+  shape-rendering: crispEdges;
+  pointer-events: none;
+  position: fixed;
+  top: 0;
+  left: 0;
+}
+
+:-moz-native-anonymous .rulers-highlighter-elements > g {
+  opacity: 0.8;
+}
+
+:-moz-native-anonymous .rulers-highlighter-elements > g > rect {
+  fill: #fff;
+}
+
+:-moz-native-anonymous .rulers-highlighter-ruler-graduations {
+  stroke: #bebebe;
+}
+
+:-moz-native-anonymous .rulers-highlighter-ruler-markers {
+  stroke: #202020;
+}
+
+:-moz-native-anonymous .rulers-highlighter-horizontal-labels > text,
+:-moz-native-anonymous .rulers-highlighter-vertical-labels > text {
+  stroke: none;
+  fill: #202020;
+  font: message-box;
+  font-size: 9px;
+  dominant-baseline: hanging;
+}
+
+:-moz-native-anonymous .rulers-highlighter-horizontal-labels > text {
+  text-anchor: start;
+}
+
+:-moz-native-anonymous .rulers-highlighter-vertical-labels > text {
+  transform: rotate(-90deg);
+  text-anchor: end;
+}
+
+/* Measuring Tool Highlighter */
+
+:-moz-native-anonymous .measuring-tool-highlighter-root {
+  position: absolute;
+  top: 0;
+  left: 0;
+  pointer-events: auto;
+  cursor: crosshair;
+}
+
+:-moz-native-anonymous .measuring-tool-highlighter-root path {
+  shape-rendering: crispEdges;
+  fill: rgba(135, 206, 235, 0.6);
+  stroke: var(--highlighter-guide-color);
+  pointer-events: none;
+}
+
+:-moz-native-anonymous .dragging path {
+  fill: rgba(135, 206, 235, 0.6);
+  stroke: var(--highlighter-guide-color);
+  opacity: 0.45;
+}
+
+:-moz-native-anonymous .measuring-tool-highlighter-label-size,
+:-moz-native-anonymous .measuring-tool-highlighter-label-position {
+  position: absolute;
+  top: 0;
+  left: 0;
+  display: inline-block;
+  border-radius: 4px;
+  padding: 4px;
+  white-space: pre-line;
+  font: message-box;
+  font-size: 10px;
+  pointer-events: none;
+  -moz-user-select: none;
+  box-sizing: border-box;
+}
+
+:-moz-native-anonymous .measuring-tool-highlighter-label-position {
+  color: #fff;
+  background: hsla(214, 13%, 24%, 0.8);
+}
+
+:-moz-native-anonymous .measuring-tool-highlighter-label-size {
+  color: var(--highlighter-bubble-text-color);
+  background: var(--highlighter-bubble-background-color);
+  border: 1px solid var(--highlighter-bubble-border-color);
+  line-height: 1.5em;
+}
+
+:-moz-native-anonymous .measuring-tool-highlighter-guide-top,
+:-moz-native-anonymous .measuring-tool-highlighter-guide-right,
+:-moz-native-anonymous .measuring-tool-highlighter-guide-bottom,
+:-moz-native-anonymous .measuring-tool-highlighter-guide-left {
+  stroke: var(--highlighter-guide-color);
+  stroke-dasharray: 5 3;
+  shape-rendering: crispEdges;
+}
+
+/* Eye Dropper */
+
+:-moz-native-anonymous .eye-dropper-root {
+  --magnifier-width: 96px;
+  --magnifier-height: 96px;
+  /* Width accounts for all color formats (hsl being the longest) */
+  --label-width: 160px;
+  --label-height: 23px;
+  --color: #e0e0e0;
+
+  position: absolute;
+  /* Tool start position. This should match the X/Y defines in JS */
+  top: 100px;
+  left: 100px;
+
+  /* Prevent interacting with the page when hovering and clicking */
+  pointer-events: auto;
+
+  /* Offset the UI so it is centered around the pointer */
+  transform: translate(
+    calc(var(--magnifier-width) / -2), calc(var(--magnifier-height) / -2));
+
+  filter: drop-shadow(0 0 1px rgba(0,0,0,.4));
+
+  /* We don't need the UI to be reversed in RTL locales, otherwise the # would appear
+     to the right of the hex code. Force LTR */
+  direction: ltr;
+}
+
+:-moz-native-anonymous .eye-dropper-canvas {
+  image-rendering: -moz-crisp-edges;
+  cursor: none;
+  width: var(--magnifier-width);
+  height: var(--magnifier-height);
+  border-radius: 50%;
+  box-shadow: 0 0 0 3px var(--color);
+  display: block;
+}
+
+:-moz-native-anonymous .eye-dropper-color-container {
+  background-color: var(--color);
+  border-radius: 2px;
+  width: var(--label-width);
+  height: var(--label-height);
+  position: relative;
+
+  --label-horizontal-center:
+    translateX(calc((var(--magnifier-width) - var(--label-width)) / 2));
+  --label-horizontal-left:
+    translateX(calc((-1 * var(--label-width) + var(--magnifier-width) / 2)));
+  --label-horizontal-right:
+    translateX(calc(var(--magnifier-width) / 2));
+  --label-vertical-top:
+    translateY(calc((-1 * var(--magnifier-height)) - var(--label-height)));
+
+  /* By default the color label container sits below the canvas.
+     Here we just center it horizontally */
+  transform: var(--label-horizontal-center);
+  transition: transform .1s ease-in-out;
+}
+
+/* If there isn't enough space below the canvas, we move the label container to the top */
+:-moz-native-anonymous .eye-dropper-root[top] .eye-dropper-color-container {
+  transform: var(--label-horizontal-center) var(--label-vertical-top);
+}
+
+/* If there isn't enough space right of the canvas to horizontally center the label
+   container, offset it to the left */
+:-moz-native-anonymous .eye-dropper-root[left] .eye-dropper-color-container {
+  transform: var(--label-horizontal-left);
+}
+:-moz-native-anonymous .eye-dropper-root[left][top] .eye-dropper-color-container {
+  transform: var(--label-horizontal-left) var(--label-vertical-top);
+}
+
+/* If there isn't enough space left of the canvas to horizontally center the label
+   container, offset it to the right */
+:-moz-native-anonymous .eye-dropper-root[right] .eye-dropper-color-container {
+  transform: var(--label-horizontal-right);
+}
+:-moz-native-anonymous .eye-dropper-root[right][top] .eye-dropper-color-container {
+  transform: var(--label-horizontal-right) var(--label-vertical-top);
+}
+
+:-moz-native-anonymous .eye-dropper-color-preview {
+  width: 16px;
+  height: 16px;
+  position: absolute;
+  offset-inline-start: 3px;
+  offset-block-start: 3px;
+  box-shadow: 0px 0px 0px black;
+  border: solid 1px #fff;
+}
+
+:-moz-native-anonymous .eye-dropper-color-value {
+  text-shadow: 1px 1px 1px #fff;
+  font: message-box;
+  font-size: 11px;
+  text-align: center;
+  padding: 4px 0;
+}
diff --git a/devtools/server/actors/highlighters.js b/devtools/server/actors/highlighters.js
new file mode 100644
index 000000000..087750ab3
--- /dev/null
+++ b/devtools/server/actors/highlighters.js
@@ -0,0 +1,715 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Ci } = require("chrome");
+
+const { XPCOMUtils } = require("resource://gre/modules/XPCOMUtils.jsm");
+const EventEmitter = require("devtools/shared/event-emitter");
+const events = require("sdk/event/core");
+const protocol = require("devtools/shared/protocol");
+const Services = require("Services");
+const { isWindowIncluded } = require("devtools/shared/layout/utils");
+const { highlighterSpec, customHighlighterSpec } = require("devtools/shared/specs/highlighters");
+const { isXUL } = require("./highlighters/utils/markup");
+const { SimpleOutlineHighlighter } = require("./highlighters/simple-outline");
+
+const HIGHLIGHTER_PICKED_TIMER = 1000;
+const IS_OSX = Services.appinfo.OS === "Darwin";
+
+/**
+ * The registration mechanism for highlighters provide a quick way to
+ * have modular highlighters, instead of a hard coded list.
+ * It allow us to split highlighers in sub modules, and add them dynamically
+ * using add-on (useful for 3rd party developers, or prototyping)
+ *
+ * Note that currently, highlighters added using add-ons, can only work on
+ * Firefox desktop, or Fennec if the same add-on is installed in both.
+ */
+const highlighterTypes = new Map();
+
+/**
+ * Returns `true` if a highlighter for the given `typeName` is registered,
+ * `false` otherwise.
+ */
+const isTypeRegistered = (typeName) => highlighterTypes.has(typeName);
+exports.isTypeRegistered = isTypeRegistered;
+
+/**
+ * Registers a given constructor as highlighter, for the `typeName` given.
+ * If no `typeName` is provided, is looking for a `typeName` property in
+ * the prototype's constructor.
+ */
+const register = (constructor, typeName = constructor.prototype.typeName) => {
+  if (!typeName) {
+    throw Error("No type's name found, or provided.");
+  }
+
+  if (highlighterTypes.has(typeName)) {
+    throw Error(`${typeName} is already registered.`);
+  }
+
+  highlighterTypes.set(typeName, constructor);
+};
+exports.register = register;
+
+/**
+ * The Highlighter is the server-side entry points for any tool that wishes to
+ * highlight elements in some way in the content document.
+ *
+ * A little bit of vocabulary:
+ * - <something>HighlighterActor classes are the actors that can be used from
+ *   the client. They do very little else than instantiate a given
+ *   <something>Highlighter and use it to highlight elements.
+ * - <something>Highlighter classes aren't actors, they're just JS classes that
+ *   know how to create and attach the actual highlighter elements on top of the
+ *   content
+ *
+ * The most used highlighter actor is the HighlighterActor which can be
+ * conveniently retrieved via the InspectorActor's 'getHighlighter' method.
+ * The InspectorActor will always return the same instance of
+ * HighlighterActor if asked several times and this instance is used in the
+ * toolbox to highlighter elements's box-model from the markup-view,
+ * box model view, console, debugger, ... as well as select elements with the
+ * pointer (pick).
+ *
+ * Other types of highlighter actors exist and can be accessed via the
+ * InspectorActor's 'getHighlighterByType' method.
+ */
+
+/**
+ * The HighlighterActor class
+ */
+var HighlighterActor = exports.HighlighterActor = protocol.ActorClassWithSpec(highlighterSpec, {
+  initialize: function (inspector, autohide) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this._autohide = autohide;
+    this._inspector = inspector;
+    this._walker = this._inspector.walker;
+    this._tabActor = this._inspector.tabActor;
+    this._highlighterEnv = new HighlighterEnvironment();
+    this._highlighterEnv.initFromTabActor(this._tabActor);
+
+    this._highlighterReady = this._highlighterReady.bind(this);
+    this._highlighterHidden = this._highlighterHidden.bind(this);
+    this._onNavigate = this._onNavigate.bind(this);
+
+    let doc = this._tabActor.window.document;
+    // Only try to create the highlighter when the document is loaded,
+    // otherwise, wait for the navigate event to fire.
+    if (doc.documentElement && doc.readyState != "uninitialized") {
+      this._createHighlighter();
+    }
+
+    // Listen to navigation events to switch from the BoxModelHighlighter to the
+    // SimpleOutlineHighlighter, and back, if the top level window changes.
+    events.on(this._tabActor, "navigate", this._onNavigate);
+  },
+
+  get conn() {
+    return this._inspector && this._inspector.conn;
+  },
+
+  form: function () {
+    return {
+      actor: this.actorID,
+      traits: {
+        autoHideOnDestroy: true
+      }
+    };
+  },
+
+  _createHighlighter: function () {
+    this._isPreviousWindowXUL = isXUL(this._tabActor.window);
+
+    if (!this._isPreviousWindowXUL) {
+      this._highlighter = new BoxModelHighlighter(this._highlighterEnv,
+                                                  this._inspector);
+      this._highlighter.on("ready", this._highlighterReady);
+      this._highlighter.on("hide", this._highlighterHidden);
+    } else {
+      this._highlighter = new SimpleOutlineHighlighter(this._highlighterEnv);
+    }
+  },
+
+  _destroyHighlighter: function () {
+    if (this._highlighter) {
+      if (!this._isPreviousWindowXUL) {
+        this._highlighter.off("ready", this._highlighterReady);
+        this._highlighter.off("hide", this._highlighterHidden);
+      }
+      this._highlighter.destroy();
+      this._highlighter = null;
+    }
+  },
+
+  _onNavigate: function ({isTopLevel}) {
+    // Skip navigation events for non top-level windows, or if the document
+    // doesn't exist anymore.
+    if (!isTopLevel || !this._tabActor.window.document.documentElement) {
+      return;
+    }
+
+    // Only rebuild the highlighter if the window type changed.
+    if (isXUL(this._tabActor.window) !== this._isPreviousWindowXUL) {
+      this._destroyHighlighter();
+      this._createHighlighter();
+    }
+  },
+
+  destroy: function () {
+    protocol.Actor.prototype.destroy.call(this);
+
+    this.hideBoxModel();
+    this._destroyHighlighter();
+    events.off(this._tabActor, "navigate", this._onNavigate);
+
+    this._highlighterEnv.destroy();
+    this._highlighterEnv = null;
+
+    this._autohide = null;
+    this._inspector = null;
+    this._walker = null;
+    this._tabActor = null;
+  },
+
+  /**
+   * Display the box model highlighting on a given NodeActor.
+   * There is only one instance of the box model highlighter, so calling this
+   * method several times won't display several highlighters, it will just move
+   * the highlighter instance to these nodes.
+   *
+   * @param NodeActor The node to be highlighted
+   * @param Options See the request part for existing options. Note that not
+   * all options may be supported by all types of highlighters.
+   */
+  showBoxModel: function (node, options = {}) {
+    if (!node || !this._highlighter.show(node.rawNode, options)) {
+      this._highlighter.hide();
+    }
+  },
+
+  /**
+   * Hide the box model highlighting if it was shown before
+   */
+  hideBoxModel: function () {
+    if (this._highlighter) {
+      this._highlighter.hide();
+    }
+  },
+
+  /**
+   * Returns `true` if the event was dispatched from a window included in
+   * the current highlighter environment; or if the highlighter environment has
+   * chrome privileges
+   *
+   * The method is specifically useful on B2G, where we do not want that events
+   * from app or main process are processed if we're inspecting the content.
+   *
+   * @param {Event} event
+   *          The event to allow
+   * @return {Boolean}
+   */
+  _isEventAllowed: function ({view}) {
+    let { window } = this._highlighterEnv;
+
+    return window instanceof Ci.nsIDOMChromeWindow ||
+          isWindowIncluded(window, view);
+  },
+
+  /**
+   * Pick a node on click, and highlight hovered nodes in the process.
+   *
+   * This method doesn't respond anything interesting, however, it starts
+   * mousemove, and click listeners on the content document to fire
+   * events and let connected clients know when nodes are hovered over or
+   * clicked.
+   *
+   * Once a node is picked, events will cease, and listeners will be removed.
+   */
+  _isPicking: false,
+  _hoveredNode: null,
+  _currentNode: null,
+
+  pick: function () {
+    if (this._isPicking) {
+      return null;
+    }
+    this._isPicking = true;
+
+    this._preventContentEvent = event => {
+      event.stopPropagation();
+      event.preventDefault();
+    };
+
+    this._onPick = event => {
+      this._preventContentEvent(event);
+
+      if (!this._isEventAllowed(event)) {
+        return;
+      }
+
+      // If shift is pressed, this is only a preview click, send the event to
+      // the client, but don't stop picking.
+      if (event.shiftKey) {
+        events.emit(this._walker, "picker-node-previewed", this._findAndAttachElement(event));
+        return;
+      }
+
+      this._stopPickerListeners();
+      this._isPicking = false;
+      if (this._autohide) {
+        this._tabActor.window.setTimeout(() => {
+          this._highlighter.hide();
+        }, HIGHLIGHTER_PICKED_TIMER);
+      }
+      if (!this._currentNode) {
+        this._currentNode = this._findAndAttachElement(event);
+      }
+      events.emit(this._walker, "picker-node-picked", this._currentNode);
+    };
+
+    this._onHovered = event => {
+      this._preventContentEvent(event);
+
+      if (!this._isEventAllowed(event)) {
+        return;
+      }
+
+      this._currentNode = this._findAndAttachElement(event);
+      if (this._hoveredNode !== this._currentNode.node) {
+        this._highlighter.show(this._currentNode.node.rawNode);
+        events.emit(this._walker, "picker-node-hovered", this._currentNode);
+        this._hoveredNode = this._currentNode.node;
+      }
+    };
+
+    this._onKey = event => {
+      if (!this._currentNode || !this._isPicking) {
+        return;
+      }
+
+      this._preventContentEvent(event);
+
+      if (!this._isEventAllowed(event)) {
+        return;
+      }
+
+      let currentNode = this._currentNode.node.rawNode;
+
+      /**
+       * KEY: Action/scope
+       * LEFT_KEY: wider or parent
+       * RIGHT_KEY: narrower or child
+       * ENTER/CARRIAGE_RETURN: Picks currentNode
+       * ESC/CTRL+SHIFT+C: Cancels picker, picks currentNode
+       */
+      switch (event.keyCode) {
+        // Wider.
+        case Ci.nsIDOMKeyEvent.DOM_VK_LEFT:
+          if (!currentNode.parentElement) {
+            return;
+          }
+          currentNode = currentNode.parentElement;
+          break;
+
+        // Narrower.
+        case Ci.nsIDOMKeyEvent.DOM_VK_RIGHT:
+          if (!currentNode.children.length) {
+            return;
+          }
+
+          // Set firstElementChild by default
+          let child = currentNode.firstElementChild;
+          // If currentNode is parent of hoveredNode, then
+          // previously selected childNode is set
+          let hoveredNode = this._hoveredNode.rawNode;
+          for (let sibling of currentNode.children) {
+            if (sibling.contains(hoveredNode) || sibling === hoveredNode) {
+              child = sibling;
+            }
+          }
+
+          currentNode = child;
+          break;
+
+        // Select the element.
+        case Ci.nsIDOMKeyEvent.DOM_VK_RETURN:
+          this._onPick(event);
+          return;
+
+        // Cancel pick mode.
+        case Ci.nsIDOMKeyEvent.DOM_VK_ESCAPE:
+          this.cancelPick();
+          events.emit(this._walker, "picker-node-canceled");
+          return;
+        case Ci.nsIDOMKeyEvent.DOM_VK_C:
+          if ((IS_OSX && event.metaKey && event.altKey) ||
+            (!IS_OSX && event.ctrlKey && event.shiftKey)) {
+            this.cancelPick();
+            events.emit(this._walker, "picker-node-canceled");
+            return;
+          }
+        default: return;
+      }
+
+      // Store currently attached element
+      this._currentNode = this._walker.attachElement(currentNode);
+      this._highlighter.show(this._currentNode.node.rawNode);
+      events.emit(this._walker, "picker-node-hovered", this._currentNode);
+    };
+
+    this._startPickerListeners();
+
+    return null;
+  },
+
+  /**
+   * This pick method also focuses the highlighter's target window.
+   */
+  pickAndFocus: function() {
+    // Go ahead and pass on the results to help future-proof this method.
+    let pickResults = this.pick();
+    this._highlighterEnv.window.focus();
+    return pickResults;
+  },
+
+  _findAndAttachElement: function (event) {
+    // originalTarget allows access to the "real" element before any retargeting
+    // is applied, such as in the case of XBL anonymous elements.  See also
+    // https://developer.mozilla.org/docs/XBL/XBL_1.0_Reference/Anonymous_Content#Event_Flow_and_Targeting
+    let node = event.originalTarget || event.target;
+    return this._walker.attachElement(node);
+  },
+
+  _startPickerListeners: function () {
+    let target = this._highlighterEnv.pageListenerTarget;
+    target.addEventListener("mousemove", this._onHovered, true);
+    target.addEventListener("click", this._onPick, true);
+    target.addEventListener("mousedown", this._preventContentEvent, true);
+    target.addEventListener("mouseup", this._preventContentEvent, true);
+    target.addEventListener("dblclick", this._preventContentEvent, true);
+    target.addEventListener("keydown", this._onKey, true);
+    target.addEventListener("keyup", this._preventContentEvent, true);
+  },
+
+  _stopPickerListeners: function () {
+    let target = this._highlighterEnv.pageListenerTarget;
+    target.removeEventListener("mousemove", this._onHovered, true);
+    target.removeEventListener("click", this._onPick, true);
+    target.removeEventListener("mousedown", this._preventContentEvent, true);
+    target.removeEventListener("mouseup", this._preventContentEvent, true);
+    target.removeEventListener("dblclick", this._preventContentEvent, true);
+    target.removeEventListener("keydown", this._onKey, true);
+    target.removeEventListener("keyup", this._preventContentEvent, true);
+  },
+
+  _highlighterReady: function () {
+    events.emit(this._inspector.walker, "highlighter-ready");
+  },
+
+  _highlighterHidden: function () {
+    events.emit(this._inspector.walker, "highlighter-hide");
+  },
+
+  cancelPick: function () {
+    if (this._isPicking) {
+      this._highlighter.hide();
+      this._stopPickerListeners();
+      this._isPicking = false;
+      this._hoveredNode = null;
+    }
+  }
+});
+
+/**
+ * A generic highlighter actor class that instantiate a highlighter given its
+ * type name and allows to show/hide it.
+ */
+var CustomHighlighterActor = exports.CustomHighlighterActor = protocol.ActorClassWithSpec(customHighlighterSpec, {
+  /**
+   * Create a highlighter instance given its typename
+   * The typename must be one of HIGHLIGHTER_CLASSES and the class must
+   * implement constructor(tabActor), show(node), hide(), destroy()
+   */
+  initialize: function (inspector, typeName) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this._inspector = inspector;
+
+    let constructor = highlighterTypes.get(typeName);
+    if (!constructor) {
+      let list = [...highlighterTypes.keys()];
+
+      throw new Error(`${typeName} isn't a valid highlighter class (${list})`);
+    }
+
+    // The assumption is that all custom highlighters need the canvasframe
+    // container to append their elements, so if this is a XUL window, bail out.
+    if (!isXUL(this._inspector.tabActor.window)) {
+      this._highlighterEnv = new HighlighterEnvironment();
+      this._highlighterEnv.initFromTabActor(inspector.tabActor);
+      this._highlighter = new constructor(this._highlighterEnv);
+    } else {
+      throw new Error("Custom " + typeName +
+        "highlighter cannot be created in a XUL window");
+    }
+  },
+
+  get conn() {
+    return this._inspector && this._inspector.conn;
+  },
+
+  destroy: function () {
+    protocol.Actor.prototype.destroy.call(this);
+    this.finalize();
+    this._inspector = null;
+  },
+
+  release: function () {},
+
+  /**
+   * Show the highlighter.
+   * This calls through to the highlighter instance's |show(node, options)|
+   * method.
+   *
+   * Most custom highlighters are made to highlight DOM nodes, hence the first
+   * NodeActor argument (NodeActor as in
+   * devtools/server/actor/inspector).
+   * Note however that some highlighters use this argument merely as a context
+   * node: the RectHighlighter for instance uses it to calculate the absolute
+   * position of the provided rect. The SelectHighlighter uses it as a base node
+   * to run the provided CSS selector on.
+   *
+   * @param {NodeActor} The node to be highlighted
+   * @param {Object} Options for the custom highlighter
+   * @return {Boolean} True, if the highlighter has been successfully shown
+   * (FF41+)
+   */
+  show: function (node, options) {
+    if (!node || !this._highlighter) {
+      return false;
+    }
+
+    return this._highlighter.show(node.rawNode, options);
+  },
+
+  /**
+   * Hide the highlighter if it was shown before
+   */
+  hide: function () {
+    if (this._highlighter) {
+      this._highlighter.hide();
+    }
+  },
+
+  /**
+   * Kill this actor. This method is called automatically just before the actor
+   * is destroyed.
+   */
+  finalize: function () {
+    if (this._highlighter) {
+      this._highlighter.destroy();
+      this._highlighter = null;
+    }
+
+    if (this._highlighterEnv) {
+      this._highlighterEnv.destroy();
+      this._highlighterEnv = null;
+    }
+  }
+});
+
+/**
+ * The HighlighterEnvironment is an object that holds all the required data for
+ * highlighters to work: the window, docShell, event listener target, ...
+ * It also emits "will-navigate" and "navigate" events, similarly to the
+ * TabActor.
+ *
+ * It can be initialized either from a TabActor (which is the most frequent way
+ * of using it, since highlighters are usually initialized by the
+ * HighlighterActor or CustomHighlighterActor, which have a tabActor reference).
+ * It can also be initialized just with a window object (which is useful for
+ * when a highlighter is used outside of the debugger server context, for
+ * instance from a gcli command).
+ */
+function HighlighterEnvironment() {
+  this.relayTabActorNavigate = this.relayTabActorNavigate.bind(this);
+  this.relayTabActorWillNavigate = this.relayTabActorWillNavigate.bind(this);
+
+  EventEmitter.decorate(this);
+}
+
+exports.HighlighterEnvironment = HighlighterEnvironment;
+
+HighlighterEnvironment.prototype = {
+  initFromTabActor: function (tabActor) {
+    this._tabActor = tabActor;
+    events.on(this._tabActor, "navigate", this.relayTabActorNavigate);
+    events.on(this._tabActor, "will-navigate", this.relayTabActorWillNavigate);
+  },
+
+  initFromWindow: function (win) {
+    this._win = win;
+
+    // We need a progress listener to know when the window will navigate/has
+    // navigated.
+    let self = this;
+    this.listener = {
+      QueryInterface: XPCOMUtils.generateQI([
+        Ci.nsIWebProgressListener,
+        Ci.nsISupportsWeakReference,
+        Ci.nsISupports
+      ]),
+
+      onStateChange: function (progress, request, flag) {
+        let isStart = flag & Ci.nsIWebProgressListener.STATE_START;
+        let isStop = flag & Ci.nsIWebProgressListener.STATE_STOP;
+        let isWindow = flag & Ci.nsIWebProgressListener.STATE_IS_WINDOW;
+        let isDocument = flag & Ci.nsIWebProgressListener.STATE_IS_DOCUMENT;
+
+        if (progress.DOMWindow !== win) {
+          return;
+        }
+
+        if (isDocument && isStart) {
+          // One of the earliest events that tells us a new URI is being loaded
+          // in this window.
+          self.emit("will-navigate", {
+            window: win,
+            isTopLevel: true
+          });
+        }
+        if (isWindow && isStop) {
+          self.emit("navigate", {
+            window: win,
+            isTopLevel: true
+          });
+        }
+      }
+    };
+
+    this.webProgress.addProgressListener(this.listener,
+      Ci.nsIWebProgress.NOTIFY_STATUS |
+      Ci.nsIWebProgress.NOTIFY_STATE_WINDOW |
+      Ci.nsIWebProgress.NOTIFY_STATE_DOCUMENT);
+  },
+
+  get isInitialized() {
+    return this._win || this._tabActor;
+  },
+
+  get isXUL() {
+    return isXUL(this.window);
+  },
+
+  get window() {
+    if (!this.isInitialized) {
+      throw new Error("Initialize HighlighterEnvironment with a tabActor " +
+        "or window first");
+    }
+    return this._tabActor ? this._tabActor.window : this._win;
+  },
+
+  get document() {
+    return this.window.document;
+  },
+
+  get docShell() {
+    return this.window.QueryInterface(Ci.nsIInterfaceRequestor)
+                      .getInterface(Ci.nsIWebNavigation)
+                      .QueryInterface(Ci.nsIDocShell);
+  },
+
+  get webProgress() {
+    return this.docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                        .getInterface(Ci.nsIWebProgress);
+  },
+
+  /**
+   * Get the right target for listening to events on the page.
+   * - If the environment was initialized from a TabActor *and* if we're in the
+   *   Browser Toolbox (to inspect firefox desktop): the tabActor is the
+   *   RootActor, in which case, the window property can be used to listen to
+   *   events.
+   * - With firefox desktop, that tabActor is a BrowserTabActor, and with B2G,
+   *   a ContentActor (which overrides BrowserTabActor). In both cases we use
+   *   the chromeEventHandler which gives us a target we can use to listen to
+   *   events, even from nested iframes.
+   * - If the environment was initialized from a window, we also use the
+   *   chromeEventHandler.
+   */
+  get pageListenerTarget() {
+    if (this._tabActor && this._tabActor.isRootActor) {
+      return this.window;
+    }
+    return this.docShell.chromeEventHandler;
+  },
+
+  relayTabActorNavigate: function (data) {
+    this.emit("navigate", data);
+  },
+
+  relayTabActorWillNavigate: function (data) {
+    this.emit("will-navigate", data);
+  },
+
+  destroy: function () {
+    if (this._tabActor) {
+      events.off(this._tabActor, "navigate", this.relayTabActorNavigate);
+      events.off(this._tabActor, "will-navigate", this.relayTabActorWillNavigate);
+    }
+
+    // In case the environment was initialized from a window, we need to remove
+    // the progress listener.
+    if (this._win) {
+      try {
+        this.webProgress.removeProgressListener(this.listener);
+      } catch (e) {
+        // Which may fail in case the window was already destroyed.
+      }
+    }
+
+    this._tabActor = null;
+    this._win = null;
+  }
+};
+
+const { BoxModelHighlighter } = require("./highlighters/box-model");
+register(BoxModelHighlighter);
+exports.BoxModelHighlighter = BoxModelHighlighter;
+
+const { CssGridHighlighter } = require("./highlighters/css-grid");
+register(CssGridHighlighter);
+exports.CssGridHighlighter = CssGridHighlighter;
+
+const { CssTransformHighlighter } = require("./highlighters/css-transform");
+register(CssTransformHighlighter);
+exports.CssTransformHighlighter = CssTransformHighlighter;
+
+const { SelectorHighlighter } = require("./highlighters/selector");
+register(SelectorHighlighter);
+exports.SelectorHighlighter = SelectorHighlighter;
+
+const { RectHighlighter } = require("./highlighters/rect");
+register(RectHighlighter);
+exports.RectHighlighter = RectHighlighter;
+
+const { GeometryEditorHighlighter } = require("./highlighters/geometry-editor");
+register(GeometryEditorHighlighter);
+exports.GeometryEditorHighlighter = GeometryEditorHighlighter;
+
+const { RulersHighlighter } = require("./highlighters/rulers");
+register(RulersHighlighter);
+exports.RulersHighlighter = RulersHighlighter;
+
+const { MeasuringToolHighlighter } = require("./highlighters/measuring-tool");
+register(MeasuringToolHighlighter);
+exports.MeasuringToolHighlighter = MeasuringToolHighlighter;
+
+const { EyeDropper } = require("./highlighters/eye-dropper");
+register(EyeDropper);
+exports.EyeDropper = EyeDropper;
diff --git a/devtools/server/actors/highlighters/auto-refresh.js b/devtools/server/actors/highlighters/auto-refresh.js
new file mode 100644
index 000000000..31f89de20
--- /dev/null
+++ b/devtools/server/actors/highlighters/auto-refresh.js
@@ -0,0 +1,215 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cu } = require("chrome");
+const EventEmitter = require("devtools/shared/event-emitter");
+const { isNodeValid } = require("./utils/markup");
+const { getAdjustedQuads } = require("devtools/shared/layout/utils");
+
+// Note that the order of items in this array is important because it is used
+// for drawing the BoxModelHighlighter's path elements correctly.
+const BOX_MODEL_REGIONS = ["margin", "border", "padding", "content"];
+
+/**
+ * Base class for auto-refresh-on-change highlighters. Sub classes will have a
+ * chance to update whenever the current node's geometry changes.
+ *
+ * Sub classes must implement the following methods:
+ * _show: called when the highlighter should be shown,
+ * _hide: called when the highlighter should be hidden,
+ * _update: called while the highlighter is shown and the geometry of the
+ *          current node changes.
+ *
+ * Sub classes will have access to the following properties:
+ * - this.currentNode: the node to be shown
+ * - this.currentQuads: all of the node's box model region quads
+ * - this.win: the current window
+ *
+ * Emits the following events:
+ * - shown
+ * - hidden
+ * - updated
+ */
+function AutoRefreshHighlighter(highlighterEnv) {
+  EventEmitter.decorate(this);
+
+  this.highlighterEnv = highlighterEnv;
+
+  this.currentNode = null;
+  this.currentQuads = {};
+
+  this.update = this.update.bind(this);
+}
+
+AutoRefreshHighlighter.prototype = {
+  /**
+   * Window corresponding to the current highlighterEnv
+   */
+  get win() {
+    if (!this.highlighterEnv) {
+      return null;
+    }
+    return this.highlighterEnv.window;
+  },
+
+  /**
+   * Show the highlighter on a given node
+   * @param {DOMNode} node
+   * @param {Object} options
+   *        Object used for passing options
+   */
+  show: function (node, options = {}) {
+    let isSameNode = node === this.currentNode;
+    let isSameOptions = this._isSameOptions(options);
+
+    if (!this._isNodeValid(node) || (isSameNode && isSameOptions)) {
+      return false;
+    }
+
+    this.options = options;
+
+    this._stopRefreshLoop();
+    this.currentNode = node;
+    this._updateAdjustedQuads();
+    this._startRefreshLoop();
+
+    let shown = this._show();
+    if (shown) {
+      this.emit("shown");
+    }
+    return shown;
+  },
+
+  /**
+   * Hide the highlighter
+   */
+  hide: function () {
+    if (!this._isNodeValid(this.currentNode)) {
+      return;
+    }
+
+    this._hide();
+    this._stopRefreshLoop();
+    this.currentNode = null;
+    this.currentQuads = {};
+    this.options = null;
+
+    this.emit("hidden");
+  },
+
+  /**
+   * Whether the current node is valid for this highlighter type.
+   * This is implemented by default to check if the node is an element node. Highlighter
+   * sub-classes should override this method if they want to highlight other node types.
+   * @param {DOMNode} node
+   * @return {Boolean}
+   */
+  _isNodeValid: function (node) {
+    return isNodeValid(node);
+  },
+
+  /**
+   * Are the provided options the same as the currently stored options?
+   * Returns false if there are no options stored currently.
+   */
+  _isSameOptions: function (options) {
+    if (!this.options) {
+      return false;
+    }
+
+    let keys = Object.keys(options);
+
+    if (keys.length !== Object.keys(this.options).length) {
+      return false;
+    }
+
+    for (let key of keys) {
+      if (this.options[key] !== options[key]) {
+        return false;
+      }
+    }
+
+    return true;
+  },
+
+  /**
+   * Update the stored box quads by reading the current node's box quads.
+   */
+  _updateAdjustedQuads: function () {
+    for (let region of BOX_MODEL_REGIONS) {
+      this.currentQuads[region] = getAdjustedQuads(
+        this.win,
+        this.currentNode, region);
+    }
+  },
+
+  /**
+   * Update the knowledge we have of the current node's boxquads and return true
+   * if any of the points x/y or bounds have change since.
+   * @return {Boolean}
+   */
+  _hasMoved: function () {
+    let oldQuads = JSON.stringify(this.currentQuads);
+    this._updateAdjustedQuads();
+    let newQuads = JSON.stringify(this.currentQuads);
+    return oldQuads !== newQuads;
+  },
+
+  /**
+   * Update the highlighter if the node has moved since the last update.
+   */
+  update: function () {
+    if (!this._isNodeValid(this.currentNode) || !this._hasMoved()) {
+      return;
+    }
+
+    this._update();
+    this.emit("updated");
+  },
+
+  _show: function () {
+    // To be implemented by sub classes
+    // When called, sub classes should actually show the highlighter for
+    // this.currentNode, potentially using options in this.options
+    throw new Error("Custom highlighter class had to implement _show method");
+  },
+
+  _update: function () {
+    // To be implemented by sub classes
+    // When called, sub classes should update the highlighter shown for
+    // this.currentNode
+    // This is called as a result of a page scroll, zoom or repaint
+    throw new Error("Custom highlighter class had to implement _update method");
+  },
+
+  _hide: function () {
+    // To be implemented by sub classes
+    // When called, sub classes should actually hide the highlighter
+    throw new Error("Custom highlighter class had to implement _hide method");
+  },
+
+  _startRefreshLoop: function () {
+    let win = this.currentNode.ownerDocument.defaultView;
+    this.rafID = win.requestAnimationFrame(this._startRefreshLoop.bind(this));
+    this.rafWin = win;
+    this.update();
+  },
+
+  _stopRefreshLoop: function () {
+    if (this.rafID && !Cu.isDeadWrapper(this.rafWin)) {
+      this.rafWin.cancelAnimationFrame(this.rafID);
+    }
+    this.rafID = this.rafWin = null;
+  },
+
+  destroy: function () {
+    this.hide();
+
+    this.highlighterEnv = null;
+    this.currentNode = null;
+  }
+};
+exports.AutoRefreshHighlighter = AutoRefreshHighlighter;
diff --git a/devtools/server/actors/highlighters/box-model.js b/devtools/server/actors/highlighters/box-model.js
new file mode 100644
index 000000000..35f201a04
--- /dev/null
+++ b/devtools/server/actors/highlighters/box-model.js
@@ -0,0 +1,712 @@
+ /* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { extend } = require("sdk/core/heritage");
+const { AutoRefreshHighlighter } = require("./auto-refresh");
+const {
+  CanvasFrameAnonymousContentHelper,
+  createNode,
+  createSVGNode,
+  getBindingElementAndPseudo,
+  hasPseudoClassLock,
+  isNodeValid,
+  moveInfobar,
+} = require("./utils/markup");
+const { setIgnoreLayoutChanges } = require("devtools/shared/layout/utils");
+const inspector = require("devtools/server/actors/inspector");
+const nodeConstants = require("devtools/shared/dom-node-constants");
+
+// Note that the order of items in this array is important because it is used
+// for drawing the BoxModelHighlighter's path elements correctly.
+const BOX_MODEL_REGIONS = ["margin", "border", "padding", "content"];
+const BOX_MODEL_SIDES = ["top", "right", "bottom", "left"];
+// Width of boxmodelhighlighter guides
+const GUIDE_STROKE_WIDTH = 1;
+// FIXME: add ":visited" and ":link" after bug 713106 is fixed
+const PSEUDO_CLASSES = [":hover", ":active", ":focus"];
+
+/**
+ * The BoxModelHighlighter draws the box model regions on top of a node.
+ * If the node is a block box, then each region will be displayed as 1 polygon.
+ * If the node is an inline box though, each region may be represented by 1 or
+ * more polygons, depending on how many line boxes the inline element has.
+ *
+ * Usage example:
+ *
+ * let h = new BoxModelHighlighter(env);
+ * h.show(node, options);
+ * h.hide();
+ * h.destroy();
+ *
+ * Available options:
+ * - region {String}
+ *   "content", "padding", "border" or "margin"
+ *   This specifies the region that the guides should outline.
+ *   Defaults to "content"
+ * - hideGuides {Boolean}
+ *   Defaults to false
+ * - hideInfoBar {Boolean}
+ *   Defaults to false
+ * - showOnly {String}
+ *   "content", "padding", "border" or "margin"
+ *   If set, only this region will be highlighted. Use with onlyRegionArea to
+ *   only highlight the area of the region.
+ * - onlyRegionArea {Boolean}
+ *   This can be set to true to make each region's box only highlight the area
+ *   of the corresponding region rather than the area of nested regions too.
+ *   This is useful when used with showOnly.
+ *
+ * Structure:
+ * <div class="highlighter-container">
+ *   <div class="box-model-root">
+ *     <svg class="box-model-elements" hidden="true">
+ *       <g class="box-model-regions">
+ *         <path class="box-model-margin" points="..." />
+ *         <path class="box-model-border" points="..." />
+ *         <path class="box-model-padding" points="..." />
+ *         <path class="box-model-content" points="..." />
+ *       </g>
+ *       <line class="box-model-guide-top" x1="..." y1="..." x2="..." y2="..." />
+ *       <line class="box-model-guide-right" x1="..." y1="..." x2="..." y2="..." />
+ *       <line class="box-model-guide-bottom" x1="..." y1="..." x2="..." y2="..." />
+ *       <line class="box-model-guide-left" x1="..." y1="..." x2="..." y2="..." />
+ *     </svg>
+ *     <div class="box-model-infobar-container">
+ *       <div class="box-model-infobar-arrow highlighter-infobar-arrow-top" />
+ *       <div class="box-model-infobar">
+ *         <div class="box-model-infobar-text" align="center">
+ *           <span class="box-model-infobar-tagname">Node name</span>
+ *           <span class="box-model-infobar-id">Node id</span>
+ *           <span class="box-model-infobar-classes">.someClass</span>
+ *           <span class="box-model-infobar-pseudo-classes">:hover</span>
+ *         </div>
+ *       </div>
+ *       <div class="box-model-infobar-arrow box-model-infobar-arrow-bottom"/>
+ *     </div>
+ *   </div>
+ * </div>
+ */
+function BoxModelHighlighter(highlighterEnv) {
+  AutoRefreshHighlighter.call(this, highlighterEnv);
+
+  this.markup = new CanvasFrameAnonymousContentHelper(this.highlighterEnv,
+    this._buildMarkup.bind(this));
+
+  /**
+   * Optionally customize each region's fill color by adding an entry to the
+   * regionFill property: `highlighter.regionFill.margin = "red";
+   */
+  this.regionFill = {};
+
+  this.onWillNavigate = this.onWillNavigate.bind(this);
+
+  this.highlighterEnv.on("will-navigate", this.onWillNavigate);
+}
+
+BoxModelHighlighter.prototype = extend(AutoRefreshHighlighter.prototype, {
+  typeName: "BoxModelHighlighter",
+
+  ID_CLASS_PREFIX: "box-model-",
+
+  _buildMarkup: function () {
+    let doc = this.win.document;
+
+    let highlighterContainer = doc.createElement("div");
+    highlighterContainer.className = "highlighter-container box-model";
+
+    // Build the root wrapper, used to adapt to the page zoom.
+    let rootWrapper = createNode(this.win, {
+      parent: highlighterContainer,
+      attributes: {
+        "id": "root",
+        "class": "root"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    // Building the SVG element with its polygons and lines
+
+    let svg = createSVGNode(this.win, {
+      nodeType: "svg",
+      parent: rootWrapper,
+      attributes: {
+        "id": "elements",
+        "width": "100%",
+        "height": "100%",
+        "hidden": "true"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    let regions = createSVGNode(this.win, {
+      nodeType: "g",
+      parent: svg,
+      attributes: {
+        "class": "regions"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    for (let region of BOX_MODEL_REGIONS) {
+      createSVGNode(this.win, {
+        nodeType: "path",
+        parent: regions,
+        attributes: {
+          "class": region,
+          "id": region
+        },
+        prefix: this.ID_CLASS_PREFIX
+      });
+    }
+
+    for (let side of BOX_MODEL_SIDES) {
+      createSVGNode(this.win, {
+        nodeType: "line",
+        parent: svg,
+        attributes: {
+          "class": "guide-" + side,
+          "id": "guide-" + side,
+          "stroke-width": GUIDE_STROKE_WIDTH
+        },
+        prefix: this.ID_CLASS_PREFIX
+      });
+    }
+
+    // Building the nodeinfo bar markup
+
+    let infobarContainer = createNode(this.win, {
+      parent: rootWrapper,
+      attributes: {
+        "class": "infobar-container",
+        "id": "infobar-container",
+        "position": "top",
+        "hidden": "true"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    let infobar = createNode(this.win, {
+      parent: infobarContainer,
+      attributes: {
+        "class": "infobar"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    let texthbox = createNode(this.win, {
+      parent: infobar,
+      attributes: {
+        "class": "infobar-text"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createNode(this.win, {
+      nodeType: "span",
+      parent: texthbox,
+      attributes: {
+        "class": "infobar-tagname",
+        "id": "infobar-tagname"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createNode(this.win, {
+      nodeType: "span",
+      parent: texthbox,
+      attributes: {
+        "class": "infobar-id",
+        "id": "infobar-id"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createNode(this.win, {
+      nodeType: "span",
+      parent: texthbox,
+      attributes: {
+        "class": "infobar-classes",
+        "id": "infobar-classes"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createNode(this.win, {
+      nodeType: "span",
+      parent: texthbox,
+      attributes: {
+        "class": "infobar-pseudo-classes",
+        "id": "infobar-pseudo-classes"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createNode(this.win, {
+      nodeType: "span",
+      parent: texthbox,
+      attributes: {
+        "class": "infobar-dimensions",
+        "id": "infobar-dimensions"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    return highlighterContainer;
+  },
+
+  /**
+   * Destroy the nodes. Remove listeners.
+   */
+  destroy: function () {
+    this.highlighterEnv.off("will-navigate", this.onWillNavigate);
+    this.markup.destroy();
+    AutoRefreshHighlighter.prototype.destroy.call(this);
+  },
+
+  getElement: function (id) {
+    return this.markup.getElement(this.ID_CLASS_PREFIX + id);
+  },
+
+  /**
+   * Override the AutoRefreshHighlighter's _isNodeValid method to also return true for
+   * text nodes since these can also be highlighted.
+   * @param {DOMNode} node
+   * @return {Boolean}
+   */
+  _isNodeValid: function (node) {
+    return node && (isNodeValid(node) || isNodeValid(node, nodeConstants.TEXT_NODE));
+  },
+
+  /**
+   * Show the highlighter on a given node
+   */
+  _show: function () {
+    if (BOX_MODEL_REGIONS.indexOf(this.options.region) == -1) {
+      this.options.region = "content";
+    }
+
+    let shown = this._update();
+    this._trackMutations();
+    this.emit("ready");
+    return shown;
+  },
+
+  /**
+   * Track the current node markup mutations so that the node info bar can be
+   * updated to reflects the node's attributes
+   */
+  _trackMutations: function () {
+    if (isNodeValid(this.currentNode)) {
+      let win = this.currentNode.ownerDocument.defaultView;
+      this.currentNodeObserver = new win.MutationObserver(this.update);
+      this.currentNodeObserver.observe(this.currentNode, {attributes: true});
+    }
+  },
+
+  _untrackMutations: function () {
+    if (isNodeValid(this.currentNode) && this.currentNodeObserver) {
+      this.currentNodeObserver.disconnect();
+      this.currentNodeObserver = null;
+    }
+  },
+
+  /**
+   * Update the highlighter on the current highlighted node (the one that was
+   * passed as an argument to show(node)).
+   * Should be called whenever node size or attributes change
+   */
+  _update: function () {
+    let shown = false;
+    setIgnoreLayoutChanges(true);
+
+    if (this._updateBoxModel()) {
+      // Show the infobar only if configured to do so and the node is an element or a text
+      // node.
+      if (!this.options.hideInfoBar && (
+          this.currentNode.nodeType === this.currentNode.ELEMENT_NODE ||
+          this.currentNode.nodeType === this.currentNode.TEXT_NODE)) {
+        this._showInfobar();
+      } else {
+        this._hideInfobar();
+      }
+      this._showBoxModel();
+      shown = true;
+    } else {
+      // Nothing to highlight (0px rectangle like a <script> tag for instance)
+      this._hide();
+    }
+
+    setIgnoreLayoutChanges(false, this.highlighterEnv.window.document.documentElement);
+
+    return shown;
+  },
+
+  /**
+   * Hide the highlighter, the outline and the infobar.
+   */
+  _hide: function () {
+    setIgnoreLayoutChanges(true);
+
+    this._untrackMutations();
+    this._hideBoxModel();
+    this._hideInfobar();
+
+    setIgnoreLayoutChanges(false, this.highlighterEnv.window.document.documentElement);
+  },
+
+  /**
+   * Hide the infobar
+   */
+  _hideInfobar: function () {
+    this.getElement("infobar-container").setAttribute("hidden", "true");
+  },
+
+  /**
+   * Show the infobar
+   */
+  _showInfobar: function () {
+    this.getElement("infobar-container").removeAttribute("hidden");
+    this._updateInfobar();
+  },
+
+  /**
+   * Hide the box model
+   */
+  _hideBoxModel: function () {
+    this.getElement("elements").setAttribute("hidden", "true");
+  },
+
+  /**
+   * Show the box model
+   */
+  _showBoxModel: function () {
+    this.getElement("elements").removeAttribute("hidden");
+  },
+
+  /**
+   * Calculate an outer quad based on the quads returned by getAdjustedQuads.
+   * The BoxModelHighlighter may highlight more than one boxes, so in this case
+   * create a new quad that "contains" all of these quads.
+   * This is useful to position the guides and infobar.
+   * This may happen if the BoxModelHighlighter is used to highlight an inline
+   * element that spans line breaks.
+   * @param {String} region The box-model region to get the outer quad for.
+   * @return {Object} A quad-like object {p1,p2,p3,p4,bounds}
+   */
+  _getOuterQuad: function (region) {
+    let quads = this.currentQuads[region];
+    if (!quads.length) {
+      return null;
+    }
+
+    let quad = {
+      p1: {x: Infinity, y: Infinity},
+      p2: {x: -Infinity, y: Infinity},
+      p3: {x: -Infinity, y: -Infinity},
+      p4: {x: Infinity, y: -Infinity},
+      bounds: {
+        bottom: -Infinity,
+        height: 0,
+        left: Infinity,
+        right: -Infinity,
+        top: Infinity,
+        width: 0,
+        x: 0,
+        y: 0,
+      }
+    };
+
+    for (let q of quads) {
+      quad.p1.x = Math.min(quad.p1.x, q.p1.x);
+      quad.p1.y = Math.min(quad.p1.y, q.p1.y);
+      quad.p2.x = Math.max(quad.p2.x, q.p2.x);
+      quad.p2.y = Math.min(quad.p2.y, q.p2.y);
+      quad.p3.x = Math.max(quad.p3.x, q.p3.x);
+      quad.p3.y = Math.max(quad.p3.y, q.p3.y);
+      quad.p4.x = Math.min(quad.p4.x, q.p4.x);
+      quad.p4.y = Math.max(quad.p4.y, q.p4.y);
+
+      quad.bounds.bottom = Math.max(quad.bounds.bottom, q.bounds.bottom);
+      quad.bounds.top = Math.min(quad.bounds.top, q.bounds.top);
+      quad.bounds.left = Math.min(quad.bounds.left, q.bounds.left);
+      quad.bounds.right = Math.max(quad.bounds.right, q.bounds.right);
+    }
+    quad.bounds.x = quad.bounds.left;
+    quad.bounds.y = quad.bounds.top;
+    quad.bounds.width = quad.bounds.right - quad.bounds.left;
+    quad.bounds.height = quad.bounds.bottom - quad.bounds.top;
+
+    return quad;
+  },
+
+  /**
+   * Update the box model as per the current node.
+   *
+   * @return {boolean}
+   *         True if the current node has a box model to be highlighted
+   */
+  _updateBoxModel: function () {
+    let options = this.options;
+    options.region = options.region || "content";
+
+    if (!this._nodeNeedsHighlighting()) {
+      this._hideBoxModel();
+      return false;
+    }
+
+    for (let i = 0; i < BOX_MODEL_REGIONS.length; i++) {
+      let boxType = BOX_MODEL_REGIONS[i];
+      let nextBoxType = BOX_MODEL_REGIONS[i + 1];
+      let box = this.getElement(boxType);
+
+      if (this.regionFill[boxType]) {
+        box.setAttribute("style", "fill:" + this.regionFill[boxType]);
+      } else {
+        box.setAttribute("style", "");
+      }
+
+      // Highlight all quads for this region by setting the "d" attribute of the
+      // corresponding <path>.
+      let path = [];
+      for (let j = 0; j < this.currentQuads[boxType].length; j++) {
+        let boxQuad = this.currentQuads[boxType][j];
+        let nextBoxQuad = this.currentQuads[nextBoxType]
+                          ? this.currentQuads[nextBoxType][j]
+                          : null;
+        path.push(this._getBoxPathCoordinates(boxQuad, nextBoxQuad));
+      }
+
+      box.setAttribute("d", path.join(" "));
+      box.removeAttribute("faded");
+
+      // If showOnly is defined, either hide the other regions, or fade them out
+      // if onlyRegionArea is set too.
+      if (options.showOnly && options.showOnly !== boxType) {
+        if (options.onlyRegionArea) {
+          box.setAttribute("faded", "true");
+        } else {
+          box.removeAttribute("d");
+        }
+      }
+
+      if (boxType === options.region && !options.hideGuides) {
+        this._showGuides(boxType);
+      } else if (options.hideGuides) {
+        this._hideGuides();
+      }
+    }
+
+    // Un-zoom the root wrapper if the page was zoomed.
+    let rootId = this.ID_CLASS_PREFIX + "root";
+    this.markup.scaleRootElement(this.currentNode, rootId);
+
+    return true;
+  },
+
+  _getBoxPathCoordinates: function (boxQuad, nextBoxQuad) {
+    let {p1, p2, p3, p4} = boxQuad;
+
+    let path;
+    if (!nextBoxQuad || !this.options.onlyRegionArea) {
+      // If this is the content box (inner-most box) or if we're not being asked
+      // to highlight only region areas, then draw a simple rectangle.
+      path = "M" + p1.x + "," + p1.y + " " +
+             "L" + p2.x + "," + p2.y + " " +
+             "L" + p3.x + "," + p3.y + " " +
+             "L" + p4.x + "," + p4.y;
+    } else {
+      // Otherwise, just draw the region itself, not a filled rectangle.
+      let {p1: np1, p2: np2, p3: np3, p4: np4} = nextBoxQuad;
+      path = "M" + p1.x + "," + p1.y + " " +
+             "L" + p2.x + "," + p2.y + " " +
+             "L" + p3.x + "," + p3.y + " " +
+             "L" + p4.x + "," + p4.y + " " +
+             "L" + p1.x + "," + p1.y + " " +
+             "L" + np1.x + "," + np1.y + " " +
+             "L" + np4.x + "," + np4.y + " " +
+             "L" + np3.x + "," + np3.y + " " +
+             "L" + np2.x + "," + np2.y + " " +
+             "L" + np1.x + "," + np1.y;
+    }
+
+    return path;
+  },
+
+  /**
+   * Can the current node be highlighted? Does it have quads.
+   * @return {Boolean}
+   */
+  _nodeNeedsHighlighting: function () {
+    return this.currentQuads.margin.length ||
+           this.currentQuads.border.length ||
+           this.currentQuads.padding.length ||
+           this.currentQuads.content.length;
+  },
+
+  _getOuterBounds: function () {
+    for (let region of ["margin", "border", "padding", "content"]) {
+      let quad = this._getOuterQuad(region);
+
+      if (!quad) {
+        // Invisible element such as a script tag.
+        break;
+      }
+
+      let {bottom, height, left, right, top, width, x, y} = quad.bounds;
+
+      if (width > 0 || height > 0) {
+        return {bottom, height, left, right, top, width, x, y};
+      }
+    }
+
+    return {
+      bottom: 0,
+      height: 0,
+      left: 0,
+      right: 0,
+      top: 0,
+      width: 0,
+      x: 0,
+      y: 0
+    };
+  },
+
+  /**
+   * We only want to show guides for horizontal and vertical edges as this helps
+   * to line them up. This method finds these edges and displays a guide there.
+   * @param {String} region The region around which the guides should be shown.
+   */
+  _showGuides: function (region) {
+    let {p1, p2, p3, p4} = this._getOuterQuad(region);
+
+    let allX = [p1.x, p2.x, p3.x, p4.x].sort((a, b) => a - b);
+    let allY = [p1.y, p2.y, p3.y, p4.y].sort((a, b) => a - b);
+    let toShowX = [];
+    let toShowY = [];
+
+    for (let arr of [allX, allY]) {
+      for (let i = 0; i < arr.length; i++) {
+        let val = arr[i];
+
+        if (i !== arr.lastIndexOf(val)) {
+          if (arr === allX) {
+            toShowX.push(val);
+          } else {
+            toShowY.push(val);
+          }
+          arr.splice(arr.lastIndexOf(val), 1);
+        }
+      }
+    }
+
+    // Move guide into place or hide it if no valid co-ordinate was found.
+    this._updateGuide("top", toShowY[0]);
+    this._updateGuide("right", toShowX[1]);
+    this._updateGuide("bottom", toShowY[1]);
+    this._updateGuide("left", toShowX[0]);
+  },
+
+  _hideGuides: function () {
+    for (let side of BOX_MODEL_SIDES) {
+      this.getElement("guide-" + side).setAttribute("hidden", "true");
+    }
+  },
+
+  /**
+   * Move a guide to the appropriate position and display it. If no point is
+   * passed then the guide is hidden.
+   *
+   * @param  {String} side
+   *         The guide to update
+   * @param  {Integer} point
+   *         x or y co-ordinate. If this is undefined we hide the guide.
+   */
+  _updateGuide: function (side, point = -1) {
+    let guide = this.getElement("guide-" + side);
+
+    if (point <= 0) {
+      guide.setAttribute("hidden", "true");
+      return false;
+    }
+
+    if (side === "top" || side === "bottom") {
+      guide.setAttribute("x1", "0");
+      guide.setAttribute("y1", point + "");
+      guide.setAttribute("x2", "100%");
+      guide.setAttribute("y2", point + "");
+    } else {
+      guide.setAttribute("x1", point + "");
+      guide.setAttribute("y1", "0");
+      guide.setAttribute("x2", point + "");
+      guide.setAttribute("y2", "100%");
+    }
+
+    guide.removeAttribute("hidden");
+
+    return true;
+  },
+
+  /**
+   * Update node information (displayName#id.class)
+   */
+  _updateInfobar: function () {
+    if (!this.currentNode) {
+      return;
+    }
+
+    let {bindingElement: node, pseudo} =
+        getBindingElementAndPseudo(this.currentNode);
+
+    // Update the tag, id, classes, pseudo-classes and dimensions
+    let displayName = inspector.getNodeDisplayName(node);
+
+    let id = node.id ? "#" + node.id : "";
+
+    let classList = (node.classList || []).length
+                    ? "." + [...node.classList].join(".")
+                    : "";
+
+    let pseudos = this._getPseudoClasses(node).join("");
+    if (pseudo) {
+      // Display :after as ::after
+      pseudos += ":" + pseudo;
+    }
+
+    let rect = this._getOuterQuad("border").bounds;
+    let dim = parseFloat(rect.width.toPrecision(6)) +
+              " \u00D7 " +
+              parseFloat(rect.height.toPrecision(6));
+
+    this.getElement("infobar-tagname").setTextContent(displayName);
+    this.getElement("infobar-id").setTextContent(id);
+    this.getElement("infobar-classes").setTextContent(classList);
+    this.getElement("infobar-pseudo-classes").setTextContent(pseudos);
+    this.getElement("infobar-dimensions").setTextContent(dim);
+
+    this._moveInfobar();
+  },
+
+  _getPseudoClasses: function (node) {
+    if (node.nodeType !== nodeConstants.ELEMENT_NODE) {
+      // hasPseudoClassLock can only be used on Elements.
+      return [];
+    }
+
+    return PSEUDO_CLASSES.filter(pseudo => hasPseudoClassLock(node, pseudo));
+  },
+
+  /**
+   * Move the Infobar to the right place in the highlighter.
+   */
+  _moveInfobar: function () {
+    let bounds = this._getOuterBounds();
+    let container = this.getElement("infobar-container");
+
+    moveInfobar(container, bounds, this.win);
+  },
+
+  onWillNavigate: function ({ isTopLevel }) {
+    if (isTopLevel) {
+      this.hide();
+    }
+  }
+});
+exports.BoxModelHighlighter = BoxModelHighlighter;
diff --git a/devtools/server/actors/highlighters/css-grid.js b/devtools/server/actors/highlighters/css-grid.js
new file mode 100644
index 000000000..0ed1ee961
--- /dev/null
+++ b/devtools/server/actors/highlighters/css-grid.js
@@ -0,0 +1,737 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const Services = require("Services");
+const { extend } = require("sdk/core/heritage");
+const { AutoRefreshHighlighter } = require("./auto-refresh");
+const {
+  CanvasFrameAnonymousContentHelper,
+  createNode,
+  createSVGNode,
+  moveInfobar,
+} = require("./utils/markup");
+const {
+  getCurrentZoom,
+  setIgnoreLayoutChanges
+} = require("devtools/shared/layout/utils");
+const { stringifyGridFragments } = require("devtools/server/actors/utils/css-grid-utils");
+
+const CSS_GRID_ENABLED_PREF = "layout.css.grid.enabled";
+const ROWS = "rows";
+const COLUMNS = "cols";
+const GRID_LINES_PROPERTIES = {
+  "edge": {
+    lineDash: [0, 0],
+    strokeStyle: "#4B0082"
+  },
+  "explicit": {
+    lineDash: [5, 3],
+    strokeStyle: "#8A2BE2"
+  },
+  "implicit": {
+    lineDash: [2, 2],
+    strokeStyle: "#9370DB"
+  }
+};
+
+// px
+const GRID_GAP_PATTERN_WIDTH = 14;
+const GRID_GAP_PATTERN_HEIGHT = 14;
+const GRID_GAP_PATTERN_LINE_DASH = [5, 3];
+const GRID_GAP_PATTERN_STROKE_STYLE = "#9370DB";
+
+/**
+ * Cached used by `CssGridHighlighter.getGridGapPattern`.
+ */
+const gCachedGridPattern = new WeakMap();
+// WeakMap key for the Row grid pattern.
+const ROW_KEY = {};
+// WeakMap key for the Column grid pattern.
+const COLUMN_KEY = {};
+
+/**
+ * The CssGridHighlighter is the class that overlays a visual grid on top of
+ * display:grid elements.
+ *
+ * Usage example:
+ * let h = new CssGridHighlighter(env);
+ * h.show(node, options);
+ * h.hide();
+ * h.destroy();
+ *
+ * Available Options:
+ * - showGridArea(areaName)
+ *     @param  {String} areaName
+ *     Shows the grid area highlight for the given area name.
+ * - showAllGridAreas
+ *     Shows all the grid area highlights for the current grid.
+ * - showGridLineNumbers(isShown)
+ *     @param  {Boolean}
+ *     Displays the grid line numbers on the grid lines if isShown is true.
+ * - showInfiniteLines(isShown)
+ *     @param  {Boolean} isShown
+ *     Displays an infinite line to represent the grid lines if isShown is true.
+ *
+ * Structure:
+ * <div class="highlighter-container">
+ *   <canvas id="css-grid-canvas" class="css-grid-canvas">
+ *   <svg class="css-grid-elements" hidden="true">
+ *     <g class="css-grid-regions">
+ *       <path class="css-grid-areas" points="..." />
+ *     </g>
+ *   </svg>
+ *   <div class="css-grid-infobar-container">
+ *     <div class="css-grid-infobar">
+ *       <div class="css-grid-infobar-text">
+ *         <span class="css-grid-infobar-areaname">Grid Area Name</span>
+ *         <span class="css-grid-infobar-dimensions"Grid Area Dimensions></span>
+ *       </div>
+ *     </div>
+ *   </div>
+ * </div>
+ */
+function CssGridHighlighter(highlighterEnv) {
+  AutoRefreshHighlighter.call(this, highlighterEnv);
+
+  this.markup = new CanvasFrameAnonymousContentHelper(this.highlighterEnv,
+    this._buildMarkup.bind(this));
+
+  this.onNavigate = this.onNavigate.bind(this);
+  this.onWillNavigate = this.onWillNavigate.bind(this);
+
+  this.highlighterEnv.on("navigate", this.onNavigate);
+  this.highlighterEnv.on("will-navigate", this.onWillNavigate);
+}
+
+CssGridHighlighter.prototype = extend(AutoRefreshHighlighter.prototype, {
+  typeName: "CssGridHighlighter",
+
+  ID_CLASS_PREFIX: "css-grid-",
+
+  _buildMarkup() {
+    let container = createNode(this.win, {
+      attributes: {
+        "class": "highlighter-container"
+      }
+    });
+
+    // We use a <canvas> element so that we can draw an arbitrary number of lines
+    // which wouldn't be possible with HTML or SVG without having to insert and remove
+    // the whole markup on every update.
+    createNode(this.win, {
+      parent: container,
+      nodeType: "canvas",
+      attributes: {
+        "id": "canvas",
+        "class": "canvas",
+        "hidden": "true"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    // Build the SVG element
+    let svg = createSVGNode(this.win, {
+      nodeType: "svg",
+      parent: container,
+      attributes: {
+        "id": "elements",
+        "width": "100%",
+        "height": "100%",
+        "hidden": "true"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    let regions = createSVGNode(this.win, {
+      nodeType: "g",
+      parent: svg,
+      attributes: {
+        "class": "regions"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    createSVGNode(this.win, {
+      nodeType: "path",
+      parent: regions,
+      attributes: {
+        "class": "areas",
+        "id": "areas"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    // Building the grid infobar markup
+    let infobarContainer = createNode(this.win, {
+      parent: container,
+      attributes: {
+        "class": "infobar-container",
+        "id": "infobar-container",
+        "position": "top",
+        "hidden": "true"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    let infobar = createNode(this.win, {
+      parent: infobarContainer,
+      attributes: {
+        "class": "infobar"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    let textbox = createNode(this.win, {
+      parent: infobar,
+      attributes: {
+        "class": "infobar-text"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createNode(this.win, {
+      nodeType: "span",
+      parent: textbox,
+      attributes: {
+        "class": "infobar-areaname",
+        "id": "infobar-areaname"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createNode(this.win, {
+      nodeType: "span",
+      parent: textbox,
+      attributes: {
+        "class": "infobar-dimensions",
+        "id": "infobar-dimensions"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    return container;
+  },
+
+  destroy() {
+    this.highlighterEnv.off("navigate", this.onNavigate);
+    this.highlighterEnv.off("will-navigate", this.onWillNavigate);
+    this.markup.destroy();
+
+    // Clear the pattern cache to avoid dead object exceptions (Bug 1342051).
+    gCachedGridPattern.delete(ROW_KEY);
+    gCachedGridPattern.delete(COLUMN_KEY);
+
+    AutoRefreshHighlighter.prototype.destroy.call(this);
+  },
+
+  getElement(id) {
+    return this.markup.getElement(this.ID_CLASS_PREFIX + id);
+  },
+
+  get ctx() {
+    return this.canvas.getCanvasContext("2d");
+  },
+
+  get canvas() {
+    return this.getElement("canvas");
+  },
+
+  /**
+   * Gets the grid gap pattern used to render the gap regions.
+   *
+   * @param  {Object} dimension
+   *         Refers to the WeakMap key for the grid dimension type which is either the
+   *         constant COLUMN or ROW.
+   * @return {CanvasPattern} grid gap pattern.
+   */
+  getGridGapPattern(dimension) {
+    if (gCachedGridPattern.has(dimension)) {
+      return gCachedGridPattern.get(dimension);
+    }
+
+    // Create the diagonal lines pattern for the rendering the grid gaps.
+    let canvas = createNode(this.win, { nodeType: "canvas" });
+    canvas.width = GRID_GAP_PATTERN_WIDTH;
+    canvas.height = GRID_GAP_PATTERN_HEIGHT;
+
+    let ctx = canvas.getContext("2d");
+    ctx.setLineDash(GRID_GAP_PATTERN_LINE_DASH);
+    ctx.beginPath();
+    ctx.translate(.5, .5);
+
+    if (dimension === COLUMN_KEY) {
+      ctx.moveTo(0, 0);
+      ctx.lineTo(GRID_GAP_PATTERN_WIDTH, GRID_GAP_PATTERN_HEIGHT);
+    } else {
+      ctx.moveTo(GRID_GAP_PATTERN_WIDTH, 0);
+      ctx.lineTo(0, GRID_GAP_PATTERN_HEIGHT);
+    }
+
+    ctx.strokeStyle = GRID_GAP_PATTERN_STROKE_STYLE;
+    ctx.stroke();
+
+    let pattern = ctx.createPattern(canvas, "repeat");
+    gCachedGridPattern.set(dimension, pattern);
+    return pattern;
+  },
+
+  /**
+   * Called when the page navigates. Used to clear the cached gap patterns and avoid
+   * using DeadWrapper objects as gap patterns the next time.
+   */
+  onNavigate() {
+    gCachedGridPattern.delete(ROW_KEY);
+    gCachedGridPattern.delete(COLUMN_KEY);
+  },
+
+  onWillNavigate({ isTopLevel }) {
+    if (isTopLevel) {
+      this.hide();
+    }
+  },
+
+  _show() {
+    if (Services.prefs.getBoolPref(CSS_GRID_ENABLED_PREF) && !this.isGrid()) {
+      this.hide();
+      return false;
+    }
+
+    return this._update();
+  },
+
+  /**
+   * Shows the grid area highlight for the given area name.
+   *
+   * @param  {String} areaName
+   *         Grid area name.
+   */
+  showGridArea(areaName) {
+    this.renderGridArea(areaName);
+    this._showGridArea();
+  },
+
+  /**
+   * Shows all the grid area highlights for the current grid.
+   */
+  showAllGridAreas() {
+    this.renderGridArea();
+    this._showGridArea();
+  },
+
+  /**
+   * Clear the grid area highlights.
+   */
+  clearGridAreas() {
+    let box = this.getElement("areas");
+    box.setAttribute("d", "");
+  },
+
+  /**
+   * Checks if the current node has a CSS Grid layout.
+   *
+   * @return  {Boolean} true if the current node has a CSS grid layout, false otherwise.
+   */
+  isGrid() {
+    return this.currentNode.getGridFragments().length > 0;
+  },
+
+  /**
+   * The AutoRefreshHighlighter's _hasMoved method returns true only if the
+   * element's quads have changed. Override it so it also returns true if the
+   * element's grid has changed (which can happen when you change the
+   * grid-template-* CSS properties with the highlighter displayed).
+   */
+  _hasMoved() {
+    let hasMoved = AutoRefreshHighlighter.prototype._hasMoved.call(this);
+
+    let oldGridData = stringifyGridFragments(this.gridData);
+    this.gridData = this.currentNode.getGridFragments();
+    let newGridData = stringifyGridFragments(this.gridData);
+
+    return hasMoved || oldGridData !== newGridData;
+  },
+
+  /**
+   * Update the highlighter on the current highlighted node (the one that was
+   * passed as an argument to show(node)).
+   * Should be called whenever node's geometry or grid changes.
+   */
+  _update() {
+    setIgnoreLayoutChanges(true);
+
+    // Clear the canvas the grid area highlights.
+    this.clearCanvas();
+    this.clearGridAreas();
+
+    // Start drawing the grid fragments.
+    for (let i = 0; i < this.gridData.length; i++) {
+      let fragment = this.gridData[i];
+      let quad = this.currentQuads.content[i];
+      this.renderFragment(fragment, quad);
+    }
+
+    // Display the grid area highlights if needed.
+    if (this.options.showAllGridAreas) {
+      this.showAllGridAreas();
+    } else if (this.options.showGridArea) {
+      this.showGridArea(this.options.showGridArea);
+    }
+
+    this._showGrid();
+
+    setIgnoreLayoutChanges(false, this.highlighterEnv.window.document.documentElement);
+    return true;
+  },
+
+  /**
+   * Update the grid information displayed in the grid info bar.
+   *
+   * @param  {GridArea} area
+   *         The grid area object.
+   * @param  {Number} x1
+   *         The first x-coordinate of the grid area rectangle.
+   * @param  {Number} x2
+   *         The second x-coordinate of the grid area rectangle.
+   * @param  {Number} y1
+   *         The first y-coordinate of the grid area rectangle.
+   * @param  {Number} y2
+   *         The second y-coordinate of the grid area rectangle.
+   */
+  _updateInfobar(area, x1, x2, y1, y2) {
+    let width = x2 - x1;
+    let height = y2 - y1;
+    let dim = parseFloat(width.toPrecision(6)) +
+              " \u00D7 " +
+              parseFloat(height.toPrecision(6));
+
+    this.getElement("infobar-areaname").setTextContent(area.name);
+    this.getElement("infobar-dimensions").setTextContent(dim);
+
+    this._moveInfobar(x1, x2, y1, y2);
+  },
+
+  /**
+   * Move the grid infobar to the right place in the highlighter.
+   *
+   * @param  {Number} x1
+   *         The first x-coordinate of the grid area rectangle.
+   * @param  {Number} x2
+   *         The second x-coordinate of the grid area rectangle.
+   * @param  {Number} y1
+   *         The first y-coordinate of the grid area rectangle.
+   * @param  {Number} y2
+   *         The second y-coordinate of the grid area rectangle.
+   */
+  _moveInfobar(x1, x2, y1, y2) {
+    let bounds = {
+      bottom: y2,
+      height: y2 - y1,
+      left: x1,
+      right: x2,
+      top: y1,
+      width: x2 - x1,
+      x: x1,
+      y: y1,
+    };
+    let container = this.getElement("infobar-container");
+
+    moveInfobar(container, bounds, this.win);
+  },
+
+  clearCanvas() {
+    let ratio = parseFloat((this.win.devicePixelRatio || 1).toFixed(2));
+    let width = this.win.innerWidth;
+    let height = this.win.innerHeight;
+
+    // Resize the canvas taking the dpr into account so as to have crisp lines.
+    this.canvas.setAttribute("width", width * ratio);
+    this.canvas.setAttribute("height", height * ratio);
+    this.canvas.setAttribute("style", `width:${width}px;height:${height}px`);
+    this.ctx.scale(ratio, ratio);
+
+    this.ctx.clearRect(0, 0, width, height);
+  },
+
+  getFirstRowLinePos(fragment) {
+    return fragment.rows.lines[0].start;
+  },
+
+  getLastRowLinePos(fragment) {
+    return fragment.rows.lines[fragment.rows.lines.length - 1].start;
+  },
+
+  getFirstColLinePos(fragment) {
+    return fragment.cols.lines[0].start;
+  },
+
+  getLastColLinePos(fragment) {
+    return fragment.cols.lines[fragment.cols.lines.length - 1].start;
+  },
+
+  /**
+   * Get the GridLine index of the last edge of the explicit grid for a grid dimension.
+   *
+   * @param  {GridTracks} tracks
+   *         The grid track of a given grid dimension.
+   * @return {Number} index of the last edge of the explicit grid for a grid dimension.
+   */
+  getLastEdgeLineIndex(tracks) {
+    let trackIndex = tracks.length - 1;
+
+    // Traverse the grid track backwards until we find an explicit track.
+    while (trackIndex >= 0 && tracks[trackIndex].type != "explicit") {
+      trackIndex--;
+    }
+
+    // The grid line index is the grid track index + 1.
+    return trackIndex + 1;
+  },
+
+  renderFragment(fragment, quad) {
+    this.renderLines(fragment.cols, quad, COLUMNS, "left", "top", "height",
+                     this.getFirstRowLinePos(fragment),
+                     this.getLastRowLinePos(fragment));
+    this.renderLines(fragment.rows, quad, ROWS, "top", "left", "width",
+                     this.getFirstColLinePos(fragment),
+                     this.getLastColLinePos(fragment));
+  },
+
+  /**
+   * Render the grid lines given the grid dimension information of the
+   * column or row lines.
+   *
+   * @param  {GridDimension} gridDimension
+   *         Column or row grid dimension object.
+   * @param  {Object} quad.bounds
+   *         The content bounds of the box model region quads.
+   * @param  {String} dimensionType
+   *         The grid dimension type which is either the constant COLUMNS or ROWS.
+   * @param  {String} mainSide
+   *         The main side of the given grid dimension - "top" for rows and
+   *         "left" for columns.
+   * @param  {String} crossSide
+   *         The cross side of the given grid dimension - "left" for rows and
+   *         "top" for columns.
+   * @param  {String} mainSize
+   *         The main size of the given grid dimension - "width" for rows and
+   *         "height" for columns.
+   * @param  {Number} startPos
+   *         The start position of the cross side of the grid dimension.
+   * @param  {Number} endPos
+   *         The end position of the cross side of the grid dimension.
+   */
+  renderLines(gridDimension, {bounds}, dimensionType, mainSide, crossSide,
+              mainSize, startPos, endPos) {
+    let lineStartPos = (bounds[crossSide] / getCurrentZoom(this.win)) + startPos;
+    let lineEndPos = (bounds[crossSide] / getCurrentZoom(this.win)) + endPos;
+
+    if (this.options.showInfiniteLines) {
+      lineStartPos = 0;
+      lineEndPos = parseInt(this.canvas.getAttribute(mainSize), 10);
+    }
+
+    let lastEdgeLineIndex = this.getLastEdgeLineIndex(gridDimension.tracks);
+
+    for (let i = 0; i < gridDimension.lines.length; i++) {
+      let line = gridDimension.lines[i];
+      let linePos = (bounds[mainSide] / getCurrentZoom(this.win)) + line.start;
+
+      if (this.options.showGridLineNumbers) {
+        this.renderGridLineNumber(line.number, linePos, lineStartPos, dimensionType);
+      }
+
+      if (i == 0 || i == lastEdgeLineIndex) {
+        this.renderLine(linePos, lineStartPos, lineEndPos, dimensionType, "edge");
+      } else {
+        this.renderLine(linePos, lineStartPos, lineEndPos, dimensionType,
+                        gridDimension.tracks[i - 1].type);
+      }
+
+      // Render a second line to illustrate the gutter for non-zero breadth.
+      if (line.breadth > 0) {
+        this.renderGridGap(linePos, lineStartPos, lineEndPos, line.breadth,
+                           dimensionType);
+        this.renderLine(linePos + line.breadth, lineStartPos, lineEndPos, dimensionType,
+                        gridDimension.tracks[i].type);
+      }
+    }
+  },
+
+  /**
+   * Render the grid line on the css grid highlighter canvas.
+   *
+   * @param  {Number} linePos
+   *         The line position along the x-axis for a column grid line and
+   *         y-axis for a row grid line.
+   * @param  {Number} startPos
+   *         The start position of the cross side of the grid line.
+   * @param  {Number} endPos
+   *         The end position of the cross side of the grid line.
+   * @param  {String} dimensionType
+   *         The grid dimension type which is either the constant COLUMNS or ROWS.
+   * @param  {[type]} lineType
+   *         The grid line type - "edge", "explicit", or "implicit".
+   */
+  renderLine(linePos, startPos, endPos, dimensionType, lineType) {
+    this.ctx.save();
+    this.ctx.setLineDash(GRID_LINES_PROPERTIES[lineType].lineDash);
+    this.ctx.beginPath();
+    this.ctx.translate(.5, .5);
+
+    if (dimensionType === COLUMNS) {
+      this.ctx.moveTo(linePos, startPos);
+      this.ctx.lineTo(linePos, endPos);
+    } else {
+      this.ctx.moveTo(startPos, linePos);
+      this.ctx.lineTo(endPos, linePos);
+    }
+
+    this.ctx.strokeStyle = GRID_LINES_PROPERTIES[lineType].strokeStyle;
+    this.ctx.stroke();
+    this.ctx.restore();
+  },
+
+  /**
+   * Render the grid line number on the css grid highlighter canvas.
+   *
+   * @param  {Number} lineNumber
+   *         The grid line number.
+   * @param  {Number} linePos
+   *         The line position along the x-axis for a column grid line and
+   *         y-axis for a row grid line.
+   * @param  {Number} startPos
+   *         The start position of the cross side of the grid line.
+   * @param  {String} dimensionType
+   *         The grid dimension type which is either the constant COLUMNS or ROWS.
+   */
+  renderGridLineNumber(lineNumber, linePos, startPos, dimensionType) {
+    this.ctx.save();
+
+    if (dimensionType === COLUMNS) {
+      this.ctx.fillText(lineNumber, linePos, startPos);
+    } else {
+      let textWidth = this.ctx.measureText(lineNumber).width;
+      this.ctx.fillText(lineNumber, startPos - textWidth, linePos);
+    }
+
+    this.ctx.restore();
+  },
+
+  /**
+   * Render the grid gap area on the css grid highlighter canvas.
+   *
+   * @param  {Number} linePos
+   *         The line position along the x-axis for a column grid line and
+   *         y-axis for a row grid line.
+   * @param  {Number} startPos
+   *         The start position of the cross side of the grid line.
+   * @param  {Number} endPos
+   *         The end position of the cross side of the grid line.
+   * @param  {Number} breadth
+   *         The grid line breadth value.
+   * @param  {String} dimensionType
+   *         The grid dimension type which is either the constant COLUMNS or ROWS.
+   */
+  renderGridGap(linePos, startPos, endPos, breadth, dimensionType) {
+    this.ctx.save();
+
+    if (dimensionType === COLUMNS) {
+      this.ctx.fillStyle = this.getGridGapPattern(COLUMN_KEY);
+      this.ctx.fillRect(linePos, startPos, breadth, endPos - startPos);
+    } else {
+      this.ctx.fillStyle = this.getGridGapPattern(ROW_KEY);
+      this.ctx.fillRect(startPos, linePos, endPos - startPos, breadth);
+    }
+
+    this.ctx.restore();
+  },
+
+  /**
+   * Render the grid area highlight for the given area name or for all the grid areas.
+   *
+   * @param  {String} areaName
+   *         Name of the grid area to be highlighted. If no area name is provided, all
+   *         the grid areas should be highlighted.
+   */
+  renderGridArea(areaName) {
+    let paths = [];
+    let currentZoom = getCurrentZoom(this.win);
+
+    for (let i = 0; i < this.gridData.length; i++) {
+      let fragment = this.gridData[i];
+      let {bounds} = this.currentQuads.content[i];
+
+      for (let area of fragment.areas) {
+        if (areaName && areaName != area.name) {
+          continue;
+        }
+
+        let rowStart = fragment.rows.lines[area.rowStart - 1];
+        let rowEnd = fragment.rows.lines[area.rowEnd - 1];
+        let columnStart = fragment.cols.lines[area.columnStart - 1];
+        let columnEnd = fragment.cols.lines[area.columnEnd - 1];
+
+        let x1 = columnStart.start + columnStart.breadth +
+          (bounds.left / currentZoom);
+        let x2 = columnEnd.start + (bounds.left / currentZoom);
+        let y1 = rowStart.start + rowStart.breadth +
+          (bounds.top / currentZoom);
+        let y2 = rowEnd.start + (bounds.top / currentZoom);
+
+        let path = "M" + x1 + "," + y1 + " " +
+                   "L" + x2 + "," + y1 + " " +
+                   "L" + x2 + "," + y2 + " " +
+                   "L" + x1 + "," + y2;
+        paths.push(path);
+
+        // Update and show the info bar when only displaying a single grid area.
+        if (areaName) {
+          this._updateInfobar(area, x1, x2, y1, y2);
+          this._showInfoBar();
+        }
+      }
+    }
+
+    let box = this.getElement("areas");
+    box.setAttribute("d", paths.join(" "));
+  },
+
+  /**
+   * Hide the highlighter, the canvas and the infobar.
+   */
+  _hide() {
+    setIgnoreLayoutChanges(true);
+    this._hideGrid();
+    this._hideGridArea();
+    this._hideInfoBar();
+    setIgnoreLayoutChanges(false, this.highlighterEnv.window.document.documentElement);
+  },
+
+  _hideGrid() {
+    this.getElement("canvas").setAttribute("hidden", "true");
+  },
+
+  _showGrid() {
+    this.getElement("canvas").removeAttribute("hidden");
+  },
+
+  _hideGridArea() {
+    this.getElement("elements").setAttribute("hidden", "true");
+  },
+
+  _showGridArea() {
+    this.getElement("elements").removeAttribute("hidden");
+  },
+
+  _hideInfoBar() {
+    this.getElement("infobar-container").setAttribute("hidden", "true");
+  },
+
+  _showInfoBar() {
+    this.getElement("infobar-container").removeAttribute("hidden");
+  },
+
+});
+
+exports.CssGridHighlighter = CssGridHighlighter;
diff --git a/devtools/server/actors/highlighters/css-transform.js b/devtools/server/actors/highlighters/css-transform.js
new file mode 100644
index 000000000..83a2c7e59
--- /dev/null
+++ b/devtools/server/actors/highlighters/css-transform.js
@@ -0,0 +1,243 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { extend } = require("sdk/core/heritage");
+const { AutoRefreshHighlighter } = require("./auto-refresh");
+const {
+  CanvasFrameAnonymousContentHelper, getComputedStyle,
+  createSVGNode, createNode } = require("./utils/markup");
+const { setIgnoreLayoutChanges,
+  getNodeBounds } = require("devtools/shared/layout/utils");
+
+// The minimum distance a line should be before it has an arrow marker-end
+const ARROW_LINE_MIN_DISTANCE = 10;
+
+var MARKER_COUNTER = 1;
+
+/**
+ * The CssTransformHighlighter is the class that draws an outline around a
+ * transformed element and an outline around where it would be if untransformed
+ * as well as arrows connecting the 2 outlines' corners.
+ */
+function CssTransformHighlighter(highlighterEnv) {
+  AutoRefreshHighlighter.call(this, highlighterEnv);
+
+  this.markup = new CanvasFrameAnonymousContentHelper(this.highlighterEnv,
+    this._buildMarkup.bind(this));
+}
+
+CssTransformHighlighter.prototype = extend(AutoRefreshHighlighter.prototype, {
+  typeName: "CssTransformHighlighter",
+
+  ID_CLASS_PREFIX: "css-transform-",
+
+  _buildMarkup: function () {
+    let container = createNode(this.win, {
+      attributes: {
+        "class": "highlighter-container"
+      }
+    });
+
+    // The root wrapper is used to unzoom the highlighter when needed.
+    let rootWrapper = createNode(this.win, {
+      parent: container,
+      attributes: {
+        "id": "root",
+        "class": "root"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    let svg = createSVGNode(this.win, {
+      nodeType: "svg",
+      parent: rootWrapper,
+      attributes: {
+        "id": "elements",
+        "hidden": "true",
+        "width": "100%",
+        "height": "100%"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    // Add a marker tag to the svg root for the arrow tip
+    this.markerId = "arrow-marker-" + MARKER_COUNTER;
+    MARKER_COUNTER++;
+    let marker = createSVGNode(this.win, {
+      nodeType: "marker",
+      parent: svg,
+      attributes: {
+        "id": this.markerId,
+        "markerWidth": "10",
+        "markerHeight": "5",
+        "orient": "auto",
+        "markerUnits": "strokeWidth",
+        "refX": "10",
+        "refY": "5",
+        "viewBox": "0 0 10 10"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createSVGNode(this.win, {
+      nodeType: "path",
+      parent: marker,
+      attributes: {
+        "d": "M 0 0 L 10 5 L 0 10 z",
+        "fill": "#08C"
+      }
+    });
+
+    let shapesGroup = createSVGNode(this.win, {
+      nodeType: "g",
+      parent: svg
+    });
+
+    // Create the 2 polygons (transformed and untransformed)
+    createSVGNode(this.win, {
+      nodeType: "polygon",
+      parent: shapesGroup,
+      attributes: {
+        "id": "untransformed",
+        "class": "untransformed"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createSVGNode(this.win, {
+      nodeType: "polygon",
+      parent: shapesGroup,
+      attributes: {
+        "id": "transformed",
+        "class": "transformed"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    // Create the arrows
+    for (let nb of ["1", "2", "3", "4"]) {
+      createSVGNode(this.win, {
+        nodeType: "line",
+        parent: shapesGroup,
+        attributes: {
+          "id": "line" + nb,
+          "class": "line",
+          "marker-end": "url(#" + this.markerId + ")"
+        },
+        prefix: this.ID_CLASS_PREFIX
+      });
+    }
+
+    return container;
+  },
+
+  /**
+   * Destroy the nodes. Remove listeners.
+   */
+  destroy: function () {
+    AutoRefreshHighlighter.prototype.destroy.call(this);
+    this.markup.destroy();
+  },
+
+  getElement: function (id) {
+    return this.markup.getElement(this.ID_CLASS_PREFIX + id);
+  },
+
+  /**
+   * Show the highlighter on a given node
+   */
+  _show: function () {
+    if (!this._isTransformed(this.currentNode)) {
+      this.hide();
+      return false;
+    }
+
+    return this._update();
+  },
+
+  /**
+   * Checks if the supplied node is transformed and not inline
+   */
+  _isTransformed: function (node) {
+    let style = getComputedStyle(node);
+    return style && (style.transform !== "none" && style.display !== "inline");
+  },
+
+  _setPolygonPoints: function (quad, id) {
+    let points = [];
+    for (let point of ["p1", "p2", "p3", "p4"]) {
+      points.push(quad[point].x + "," + quad[point].y);
+    }
+    this.getElement(id).setAttribute("points", points.join(" "));
+  },
+
+  _setLinePoints: function (p1, p2, id) {
+    let line = this.getElement(id);
+    line.setAttribute("x1", p1.x);
+    line.setAttribute("y1", p1.y);
+    line.setAttribute("x2", p2.x);
+    line.setAttribute("y2", p2.y);
+
+    let dist = Math.sqrt(Math.pow(p2.x - p1.x, 2) + Math.pow(p2.y - p1.y, 2));
+    if (dist < ARROW_LINE_MIN_DISTANCE) {
+      line.removeAttribute("marker-end");
+    } else {
+      line.setAttribute("marker-end", "url(#" + this.markerId + ")");
+    }
+  },
+
+  /**
+   * Update the highlighter on the current highlighted node (the one that was
+   * passed as an argument to show(node)).
+   * Should be called whenever node size or attributes change
+   */
+  _update: function () {
+    setIgnoreLayoutChanges(true);
+
+    // Getting the points for the transformed shape
+    let quads = this.currentQuads.border;
+    if (!quads.length ||
+        quads[0].bounds.width <= 0 || quads[0].bounds.height <= 0) {
+      this._hideShapes();
+      return false;
+    }
+
+    let [quad] = quads;
+
+    // Getting the points for the untransformed shape
+    let untransformedQuad = getNodeBounds(this.win, this.currentNode);
+
+    this._setPolygonPoints(quad, "transformed");
+    this._setPolygonPoints(untransformedQuad, "untransformed");
+    for (let nb of ["1", "2", "3", "4"]) {
+      this._setLinePoints(untransformedQuad["p" + nb], quad["p" + nb], "line" + nb);
+    }
+
+    // Adapt to the current zoom
+    this.markup.scaleRootElement(this.currentNode, this.ID_CLASS_PREFIX + "root");
+
+    this._showShapes();
+
+    setIgnoreLayoutChanges(false, this.highlighterEnv.window.document.documentElement);
+    return true;
+  },
+
+  /**
+   * Hide the highlighter, the outline and the infobar.
+   */
+  _hide: function () {
+    setIgnoreLayoutChanges(true);
+    this._hideShapes();
+    setIgnoreLayoutChanges(false, this.highlighterEnv.window.document.documentElement);
+  },
+
+  _hideShapes: function () {
+    this.getElement("elements").setAttribute("hidden", "true");
+  },
+
+  _showShapes: function () {
+    this.getElement("elements").removeAttribute("hidden");
+  }
+});
+exports.CssTransformHighlighter = CssTransformHighlighter;
diff --git a/devtools/server/actors/highlighters/eye-dropper.js b/devtools/server/actors/highlighters/eye-dropper.js
new file mode 100644
index 000000000..a90ec22bd
--- /dev/null
+++ b/devtools/server/actors/highlighters/eye-dropper.js
@@ -0,0 +1,534 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+// Eye-dropper tool. This is implemented as a highlighter so it can be displayed in the
+// content page.
+// It basically displays a magnifier that tracks mouse moves and shows a magnified version
+// of the page. On click, it samples the color at the pixel being hovered.
+
+const {Ci, Cc} = require("chrome");
+const {CanvasFrameAnonymousContentHelper, createNode} = require("./utils/markup");
+const Services = require("Services");
+const EventEmitter = require("devtools/shared/event-emitter");
+const {rgbToHsl, rgbToColorName} = require("devtools/shared/css/color").colorUtils;
+const {getCurrentZoom, getFrameOffsets} = require("devtools/shared/layout/utils");
+
+loader.lazyGetter(this, "clipboardHelper",
+  () => Cc["@mozilla.org/widget/clipboardhelper;1"].getService(Ci.nsIClipboardHelper));
+loader.lazyGetter(this, "l10n",
+  () => Services.strings.createBundle("chrome://devtools/locale/eyedropper.properties"));
+
+const ZOOM_LEVEL_PREF = "devtools.eyedropper.zoom";
+const FORMAT_PREF = "devtools.defaultColorUnit";
+// Width of the canvas.
+const MAGNIFIER_WIDTH = 96;
+// Height of the canvas.
+const MAGNIFIER_HEIGHT = 96;
+// Start position, when the tool is first shown. This should match the top/left position
+// defined in CSS.
+const DEFAULT_START_POS_X = 100;
+const DEFAULT_START_POS_Y = 100;
+// How long to wait before closing after copy.
+const CLOSE_DELAY = 750;
+
+/**
+ * The EyeDropper is the class that draws the gradient line and
+ * color stops as an overlay on top of a linear-gradient background-image.
+ */
+function EyeDropper(highlighterEnv) {
+  EventEmitter.decorate(this);
+
+  this.highlighterEnv = highlighterEnv;
+  this.markup = new CanvasFrameAnonymousContentHelper(this.highlighterEnv,
+                                                      this._buildMarkup.bind(this));
+
+  // Get a couple of settings from prefs.
+  this.format = Services.prefs.getCharPref(FORMAT_PREF);
+  this.eyeDropperZoomLevel = Services.prefs.getIntPref(ZOOM_LEVEL_PREF);
+}
+
+EyeDropper.prototype = {
+  typeName: "EyeDropper",
+
+  ID_CLASS_PREFIX: "eye-dropper-",
+
+  get win() {
+    return this.highlighterEnv.window;
+  },
+
+  _buildMarkup() {
+    // Highlighter main container.
+    let container = createNode(this.win, {
+      attributes: {"class": "highlighter-container"}
+    });
+
+    // Wrapper element.
+    let wrapper = createNode(this.win, {
+      parent: container,
+      attributes: {
+        "id": "root",
+        "class": "root",
+        "hidden": "true"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    // The magnifier canvas element.
+    createNode(this.win, {
+      parent: wrapper,
+      nodeType: "canvas",
+      attributes: {
+        "id": "canvas",
+        "class": "canvas",
+        "width": MAGNIFIER_WIDTH,
+        "height": MAGNIFIER_HEIGHT
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    // The color label element.
+    let colorLabelContainer = createNode(this.win, {
+      parent: wrapper,
+      attributes: {"class": "color-container"},
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createNode(this.win, {
+      nodeType: "div",
+      parent: colorLabelContainer,
+      attributes: {"id": "color-preview", "class": "color-preview"},
+      prefix: this.ID_CLASS_PREFIX
+    });
+    createNode(this.win, {
+      nodeType: "div",
+      parent: colorLabelContainer,
+      attributes: {"id": "color-value", "class": "color-value"},
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    return container;
+  },
+
+  destroy() {
+    this.hide();
+    this.markup.destroy();
+  },
+
+  getElement(id) {
+    return this.markup.getElement(this.ID_CLASS_PREFIX + id);
+  },
+
+  /**
+   * Show the eye-dropper highlighter.
+   * @param {DOMNode} node The node which document the highlighter should be inserted in.
+   * @param {Object} options The options object may contain the following properties:
+   * - {Boolean} copyOnSelect Whether selecting a color should copy it to the clipboard.
+   */
+  show(node, options = {}) {
+    if (this.highlighterEnv.isXUL) {
+      return false;
+    }
+
+    this.options = options;
+
+    // Get the page's current zoom level.
+    this.pageZoom = getCurrentZoom(this.win);
+
+    // Take a screenshot of the viewport. This needs to be done first otherwise the
+    // eyedropper UI will appear in the screenshot itself (since the UI is injected as
+    // native anonymous content in the page).
+    // Once the screenshot is ready, the magnified area will be drawn.
+    this.prepareImageCapture();
+
+    // Start listening for user events.
+    let {pageListenerTarget} = this.highlighterEnv;
+    pageListenerTarget.addEventListener("mousemove", this);
+    pageListenerTarget.addEventListener("click", this, true);
+    pageListenerTarget.addEventListener("keydown", this);
+    pageListenerTarget.addEventListener("DOMMouseScroll", this);
+    pageListenerTarget.addEventListener("FullZoomChange", this);
+
+    // Show the eye-dropper.
+    this.getElement("root").removeAttribute("hidden");
+
+    // Prepare the canvas context on which we're drawing the magnified page portion.
+    this.ctx = this.getElement("canvas").getCanvasContext();
+    this.ctx.imageSmoothingEnabled = false;
+
+    this.magnifiedArea = {width: MAGNIFIER_WIDTH, height: MAGNIFIER_HEIGHT,
+                          x: DEFAULT_START_POS_X, y: DEFAULT_START_POS_Y};
+
+    this.moveTo(DEFAULT_START_POS_X, DEFAULT_START_POS_Y);
+
+    // Focus the content so the keyboard can be used.
+    this.win.focus();
+
+    return true;
+  },
+
+  /**
+   * Hide the eye-dropper highlighter.
+   */
+  hide() {
+    if (this.highlighterEnv.isXUL) {
+      return;
+    }
+
+    this.pageImage = null;
+
+    let {pageListenerTarget} = this.highlighterEnv;
+    pageListenerTarget.removeEventListener("mousemove", this);
+    pageListenerTarget.removeEventListener("click", this, true);
+    pageListenerTarget.removeEventListener("keydown", this);
+    pageListenerTarget.removeEventListener("DOMMouseScroll", this);
+    pageListenerTarget.removeEventListener("FullZoomChange", this);
+
+    this.getElement("root").setAttribute("hidden", "true");
+    this.getElement("root").removeAttribute("drawn");
+
+    this.emit("hidden");
+  },
+
+  prepareImageCapture() {
+    // Get the image data from the content window.
+    let imageData = getWindowAsImageData(this.win);
+
+    // We need to transform imageData to something drawWindow will consume. An ImageBitmap
+    // works well. We could have used an Image, but doing so results in errors if the page
+    // defines CSP headers.
+    this.win.createImageBitmap(imageData).then(image => {
+      this.pageImage = image;
+      // We likely haven't drawn anything yet (no mousemove events yet), so start now.
+      this.draw();
+
+      // Set an attribute on the root element to be able to run tests after the first draw
+      // was done.
+      this.getElement("root").setAttribute("drawn", "true");
+    });
+  },
+
+  /**
+   * Get the number of cells (blown-up pixels) per direction in the grid.
+   */
+  get cellsWide() {
+    // Canvas will render whole "pixels" (cells) only, and an even number at that. Round
+    // up to the nearest even number of pixels.
+    let cellsWide = Math.ceil(this.magnifiedArea.width / this.eyeDropperZoomLevel);
+    cellsWide += cellsWide % 2;
+
+    return cellsWide;
+  },
+
+  /**
+   * Get the size of each cell (blown-up pixel) in the grid.
+   */
+  get cellSize() {
+    return this.magnifiedArea.width / this.cellsWide;
+  },
+
+  /**
+   * Get index of cell in the center of the grid.
+   */
+  get centerCell() {
+    return Math.floor(this.cellsWide / 2);
+  },
+
+  /**
+   * Get color of center cell in the grid.
+   */
+  get centerColor() {
+    let pos = (this.centerCell * this.cellSize) + (this.cellSize / 2);
+    let rgb = this.ctx.getImageData(pos, pos, 1, 1).data;
+    return rgb;
+  },
+
+  draw() {
+    // If the image of the page isn't ready yet, bail out, we'll draw later on mousemove.
+    if (!this.pageImage) {
+      return;
+    }
+
+    let {width, height, x, y} = this.magnifiedArea;
+
+    let zoomedWidth = width / this.eyeDropperZoomLevel;
+    let zoomedHeight = height / this.eyeDropperZoomLevel;
+
+    let sx = x - (zoomedWidth / 2);
+    let sy = y - (zoomedHeight / 2);
+    let sw = zoomedWidth;
+    let sh = zoomedHeight;
+
+    this.ctx.drawImage(this.pageImage, sx, sy, sw, sh, 0, 0, width, height);
+
+    // Draw the grid on top, but only at 3x or more, otherwise it's too busy.
+    if (this.eyeDropperZoomLevel > 2) {
+      this.drawGrid();
+    }
+
+    this.drawCrosshair();
+
+    // Update the color preview and value.
+    let rgb = this.centerColor;
+    this.getElement("color-preview").setAttribute("style",
+      `background-color:${toColorString(rgb, "rgb")};`);
+    this.getElement("color-value").setTextContent(toColorString(rgb, this.format));
+  },
+
+  /**
+   * Draw a grid on the canvas representing pixel boundaries.
+   */
+  drawGrid() {
+    let {width, height} = this.magnifiedArea;
+
+    this.ctx.lineWidth = 1;
+    this.ctx.strokeStyle = "rgba(143, 143, 143, 0.2)";
+
+    for (let i = 0; i < width; i += this.cellSize) {
+      this.ctx.beginPath();
+      this.ctx.moveTo(i - .5, 0);
+      this.ctx.lineTo(i - .5, height);
+      this.ctx.stroke();
+
+      this.ctx.beginPath();
+      this.ctx.moveTo(0, i - .5);
+      this.ctx.lineTo(width, i - .5);
+      this.ctx.stroke();
+    }
+  },
+
+  /**
+   * Draw a box on the canvas to highlight the center cell.
+   */
+  drawCrosshair() {
+    let pos = this.centerCell * this.cellSize;
+
+    this.ctx.lineWidth = 1;
+    this.ctx.lineJoin = "miter";
+    this.ctx.strokeStyle = "rgba(0, 0, 0, 1)";
+    this.ctx.strokeRect(pos - 1.5, pos - 1.5, this.cellSize + 2, this.cellSize + 2);
+
+    this.ctx.strokeStyle = "rgba(255, 255, 255, 1)";
+    this.ctx.strokeRect(pos - 0.5, pos - 0.5, this.cellSize, this.cellSize);
+  },
+
+  handleEvent(e) {
+    switch (e.type) {
+      case "mousemove":
+        // We might be getting an event from a child frame, so account for the offset.
+        let [xOffset, yOffset] = getFrameOffsets(this.win, e.target);
+        let x = xOffset + e.pageX - this.win.scrollX;
+        let y = yOffset + e.pageY - this.win.scrollY;
+        // Update the zoom area.
+        this.magnifiedArea.x = x * this.pageZoom;
+        this.magnifiedArea.y = y * this.pageZoom;
+        // Redraw the portion of the screenshot that is now under the mouse.
+        this.draw();
+        // And move the eye-dropper's UI so it follows the mouse.
+        this.moveTo(x, y);
+        break;
+      case "click":
+        this.selectColor();
+        break;
+      case "keydown":
+        this.handleKeyDown(e);
+        break;
+      case "DOMMouseScroll":
+        // Prevent scrolling. That's because we only took a screenshot of the viewport, so
+        // scrolling out of the viewport wouldn't draw the expected things. In the future
+        // we can take the screenshot again on scroll, but for now it doesn't seem
+        // important.
+        e.preventDefault();
+        break;
+      case "FullZoomChange":
+        this.hide();
+        this.show();
+        break;
+    }
+  },
+
+  moveTo(x, y) {
+    let root = this.getElement("root");
+    root.setAttribute("style", `top:${y}px;left:${x}px;`);
+
+    // Move the label container to the top if the magnifier is close to the bottom edge.
+    if (y >= this.win.innerHeight - MAGNIFIER_HEIGHT) {
+      root.setAttribute("top", "");
+    } else {
+      root.removeAttribute("top");
+    }
+
+    // Also offset the label container to the right or left if the magnifier is close to
+    // the edge.
+    root.removeAttribute("left");
+    root.removeAttribute("right");
+    if (x <= MAGNIFIER_WIDTH) {
+      root.setAttribute("right", "");
+    } else if (x >= this.win.innerWidth - MAGNIFIER_WIDTH) {
+      root.setAttribute("left", "");
+    }
+  },
+
+  /**
+   * Select the current color that's being previewed. Depending on the current options,
+   * selecting might mean copying to the clipboard and closing the
+   */
+  selectColor() {
+    let onColorSelected = Promise.resolve();
+    if (this.options.copyOnSelect) {
+      onColorSelected = this.copyColor();
+    }
+
+    this.emit("selected", toColorString(this.centerColor, this.format));
+    onColorSelected.then(() => this.hide(), e => console.error(e));
+  },
+
+  /**
+   * Handler for the keydown event. Either select the color or move the panel in a
+   * direction depending on the key pressed.
+   */
+  handleKeyDown(e) {
+    // Bail out early if any unsupported modifier is used, so that we let
+    // keyboard shortcuts through.
+    if (e.metaKey || e.ctrlKey || e.altKey) {
+      return;
+    }
+
+    if (e.keyCode === e.DOM_VK_RETURN) {
+      this.selectColor();
+      e.preventDefault();
+      return;
+    }
+
+    if (e.keyCode === e.DOM_VK_ESCAPE) {
+      this.emit("canceled");
+      this.hide();
+      e.preventDefault();
+      return;
+    }
+
+    let offsetX = 0;
+    let offsetY = 0;
+    let modifier = 1;
+
+    if (e.keyCode === e.DOM_VK_LEFT) {
+      offsetX = -1;
+    } else if (e.keyCode === e.DOM_VK_RIGHT) {
+      offsetX = 1;
+    } else if (e.keyCode === e.DOM_VK_UP) {
+      offsetY = -1;
+    } else if (e.keyCode === e.DOM_VK_DOWN) {
+      offsetY = 1;
+    }
+
+    if (e.shiftKey) {
+      modifier = 10;
+    }
+
+    offsetY *= modifier;
+    offsetX *= modifier;
+
+    if (offsetX !== 0 || offsetY !== 0) {
+      this.magnifiedArea.x = cap(this.magnifiedArea.x + offsetX,
+                                 0, this.win.innerWidth * this.pageZoom);
+      this.magnifiedArea.y = cap(this.magnifiedArea.y + offsetY, 0,
+                                 this.win.innerHeight * this.pageZoom);
+
+      this.draw();
+
+      this.moveTo(this.magnifiedArea.x / this.pageZoom,
+                  this.magnifiedArea.y / this.pageZoom);
+
+      e.preventDefault();
+    }
+  },
+
+  /**
+   * Copy the currently inspected color to the clipboard.
+   * @return {Promise} Resolves when the copy has been done (after a delay that is used to
+   * let users know that something was copied).
+   */
+  copyColor() {
+    // Copy to the clipboard.
+    let color = toColorString(this.centerColor, this.format);
+    clipboardHelper.copyString(color);
+
+    // Provide some feedback.
+    this.getElement("color-value").setTextContent(
+      "✓ " + l10n.GetStringFromName("colorValue.copied"));
+
+    // Hide the tool after a delay.
+    clearTimeout(this._copyTimeout);
+    return new Promise(resolve => {
+      this._copyTimeout = setTimeout(resolve, CLOSE_DELAY);
+    });
+  }
+};
+
+exports.EyeDropper = EyeDropper;
+
+/**
+ * Draw the visible portion of the window on a canvas and get the resulting ImageData.
+ * @param {Window} win
+ * @return {ImageData} The image data for the window.
+ */
+function getWindowAsImageData(win) {
+  let canvas = win.document.createElementNS("http://www.w3.org/1999/xhtml", "canvas");
+  let scale = getCurrentZoom(win);
+  let width = win.innerWidth;
+  let height = win.innerHeight;
+  canvas.width = width * scale;
+  canvas.height = height * scale;
+  canvas.mozOpaque = true;
+
+  let ctx = canvas.getContext("2d");
+
+  ctx.scale(scale, scale);
+  ctx.drawWindow(win, win.scrollX, win.scrollY, width, height, "#fff");
+
+  return ctx.getImageData(0, 0, canvas.width, canvas.height);
+}
+
+/**
+ * Get a formatted CSS color string from a color value.
+ * @param {array} rgb Rgb values of a color to format.
+ * @param {string} format Format of string. One of "hex", "rgb", "hsl", "name".
+ * @return {string} Formatted color value, e.g. "#FFF" or "hsl(20, 10%, 10%)".
+ */
+function toColorString(rgb, format) {
+  let [r, g, b] = rgb;
+
+  switch (format) {
+    case "hex":
+      return hexString(rgb);
+    case "rgb":
+      return "rgb(" + r + ", " + g + ", " + b + ")";
+    case "hsl":
+      let [h, s, l] = rgbToHsl(rgb);
+      return "hsl(" + h + ", " + s + "%, " + l + "%)";
+    case "name":
+      let str;
+      try {
+        str = rgbToColorName(r, g, b);
+      } catch (e) {
+        str = hexString(rgb);
+      }
+      return str;
+    default:
+      return hexString(rgb);
+  }
+}
+
+/**
+ * Produce a hex-formatted color string from rgb values.
+ * @param {array} rgb Rgb values of color to stringify.
+ * @return {string} Hex formatted string for color, e.g. "#FFEE00".
+ */
+function hexString([r, g, b]) {
+  let val = (1 << 24) + (r << 16) + (g << 8) + (b << 0);
+  return "#" + val.toString(16).substr(-6).toUpperCase();
+}
+
+function cap(value, min, max) {
+  return Math.max(min, Math.min(value, max));
+}
diff --git a/devtools/server/actors/highlighters/geometry-editor.js b/devtools/server/actors/highlighters/geometry-editor.js
new file mode 100644
index 000000000..35b33eec1
--- /dev/null
+++ b/devtools/server/actors/highlighters/geometry-editor.js
@@ -0,0 +1,704 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { extend } = require("sdk/core/heritage");
+const { AutoRefreshHighlighter } = require("./auto-refresh");
+const { CanvasFrameAnonymousContentHelper, getCSSStyleRules, getComputedStyle,
+        createSVGNode, createNode } = require("./utils/markup");
+const { setIgnoreLayoutChanges, getAdjustedQuads } = require("devtools/shared/layout/utils");
+
+const GEOMETRY_LABEL_SIZE = 6;
+
+// List of all DOM Events subscribed directly to the document from the
+// Geometry Editor highlighter
+const DOM_EVENTS = ["mousemove", "mouseup", "pagehide"];
+
+const _dragging = Symbol("geometry/dragging");
+
+/**
+ * Element geometry properties helper that gives names of position and size
+ * properties.
+ */
+var GeoProp = {
+  SIDES: ["top", "right", "bottom", "left"],
+  SIZES: ["width", "height"],
+
+  allProps: function () {
+    return [...this.SIDES, ...this.SIZES];
+  },
+
+  isSide: function (name) {
+    return this.SIDES.indexOf(name) !== -1;
+  },
+
+  isSize: function (name) {
+    return this.SIZES.indexOf(name) !== -1;
+  },
+
+  containsSide: function (names) {
+    return names.some(name => this.SIDES.indexOf(name) !== -1);
+  },
+
+  containsSize: function (names) {
+    return names.some(name => this.SIZES.indexOf(name) !== -1);
+  },
+
+  isHorizontal: function (name) {
+    return name === "left" || name === "right" || name === "width";
+  },
+
+  isInverted: function (name) {
+    return name === "right" || name === "bottom";
+  },
+
+  mainAxisStart: function (name) {
+    return this.isHorizontal(name) ? "left" : "top";
+  },
+
+  crossAxisStart: function (name) {
+    return this.isHorizontal(name) ? "top" : "left";
+  },
+
+  mainAxisSize: function (name) {
+    return this.isHorizontal(name) ? "width" : "height";
+  },
+
+  crossAxisSize: function (name) {
+    return this.isHorizontal(name) ? "height" : "width";
+  },
+
+  axis: function (name) {
+    return this.isHorizontal(name) ? "x" : "y";
+  },
+
+  crossAxis: function (name) {
+    return this.isHorizontal(name) ? "y" : "x";
+  }
+};
+
+/**
+ * Get the provided node's offsetParent dimensions.
+ * Returns an object with the {parent, dimension} properties.
+ * Note that the returned parent will be null if the offsetParent is the
+ * default, non-positioned, body or html node.
+ *
+ * node.offsetParent returns the nearest positioned ancestor but if it is
+ * non-positioned itself, we just return null to let consumers know the node is
+ * actually positioned relative to the viewport.
+ *
+ * @return {Object}
+ */
+function getOffsetParent(node) {
+  let win = node.ownerDocument.defaultView;
+
+  let offsetParent = node.offsetParent;
+  if (offsetParent &&
+      getComputedStyle(offsetParent).position === "static") {
+    offsetParent = null;
+  }
+
+  let width, height;
+  if (!offsetParent) {
+    height = win.innerHeight;
+    width = win.innerWidth;
+  } else {
+    height = offsetParent.offsetHeight;
+    width = offsetParent.offsetWidth;
+  }
+
+  return {
+    element: offsetParent,
+    dimension: {width, height}
+  };
+}
+
+/**
+ * Get the list of geometry properties that are actually set on the provided
+ * node.
+ *
+ * @param {nsIDOMNode} node The node to analyze.
+ * @return {Map} A map indexed by property name and where the value is an
+ * object having the cssRule property.
+ */
+function getDefinedGeometryProperties(node) {
+  let props = new Map();
+  if (!node) {
+    return props;
+  }
+
+  // Get the list of css rules applying to the current node.
+  let cssRules = getCSSStyleRules(node);
+  for (let i = 0; i < cssRules.Count(); i++) {
+    let rule = cssRules.GetElementAt(i);
+    for (let name of GeoProp.allProps()) {
+      let value = rule.style.getPropertyValue(name);
+      if (value && value !== "auto") {
+        // getCSSStyleRules returns rules ordered from least to most specific
+        // so just override any previous properties we have set.
+        props.set(name, {
+          cssRule: rule
+        });
+      }
+    }
+  }
+
+  // Go through the inline styles last, only if the node supports inline style
+  // (e.g. pseudo elements don't have a style property)
+  if (node.style) {
+    for (let name of GeoProp.allProps()) {
+      let value = node.style.getPropertyValue(name);
+      if (value && value !== "auto") {
+        props.set(name, {
+          // There's no cssRule to store here, so store the node instead since
+          // node.style exists.
+          cssRule: node
+        });
+      }
+    }
+  }
+
+  // Post-process the list for invalid properties. This is done after the fact
+  // because of cases like relative positioning with both top and bottom where
+  // only top will actually be used, but both exists in css rules and computed
+  // styles.
+  let { position } = getComputedStyle(node);
+  for (let [name] of props) {
+    // Top/left/bottom/right on static positioned elements have no effect.
+    if (position === "static" && GeoProp.SIDES.indexOf(name) !== -1) {
+      props.delete(name);
+    }
+
+    // Bottom/right on relative positioned elements are only used if top/left
+    // are not defined.
+    let hasRightAndLeft = name === "right" && props.has("left");
+    let hasBottomAndTop = name === "bottom" && props.has("top");
+    if (position === "relative" && (hasRightAndLeft || hasBottomAndTop)) {
+      props.delete(name);
+    }
+  }
+
+  return props;
+}
+exports.getDefinedGeometryProperties = getDefinedGeometryProperties;
+
+/**
+ * The GeometryEditor highlights an elements's top, left, bottom, right, width
+ * and height dimensions, when they are set.
+ *
+ * To determine if an element has a set size and position, the highlighter lists
+ * the CSS rules that apply to the element and checks for the top, left, bottom,
+ * right, width and height properties.
+ * The highlighter won't be shown if the element doesn't have any of these
+ * properties set, but will be shown when at least 1 property is defined.
+ *
+ * The highlighter displays lines and labels for each of the defined properties
+ * in and around the element (relative to the offset parent when one exists).
+ * The highlighter also highlights the element itself and its offset parent if
+ * there is one.
+ *
+ * Note that the class name contains the word Editor because the aim is for the
+ * handles to be draggable in content to make the geometry editable.
+ */
+function GeometryEditorHighlighter(highlighterEnv) {
+  AutoRefreshHighlighter.call(this, highlighterEnv);
+
+  // The list of element geometry properties that can be set.
+  this.definedProperties = new Map();
+
+  this.markup = new CanvasFrameAnonymousContentHelper(highlighterEnv,
+    this._buildMarkup.bind(this));
+
+  let { pageListenerTarget } = this.highlighterEnv;
+
+  // Register the geometry editor instance to all events we're interested in.
+  DOM_EVENTS.forEach(type => pageListenerTarget.addEventListener(type, this));
+
+  // Register the mousedown event for each Geometry Editor's handler.
+  // Those events are automatically removed when the markup is destroyed.
+  let onMouseDown = this.handleEvent.bind(this);
+
+  for (let side of GeoProp.SIDES) {
+    this.getElement("handler-" + side)
+      .addEventListener("mousedown", onMouseDown);
+  }
+}
+
+GeometryEditorHighlighter.prototype = extend(AutoRefreshHighlighter.prototype, {
+  typeName: "GeometryEditorHighlighter",
+
+  ID_CLASS_PREFIX: "geometry-editor-",
+
+  _buildMarkup: function () {
+    let container = createNode(this.win, {
+      attributes: {"class": "highlighter-container"}
+    });
+
+    let root = createNode(this.win, {
+      parent: container,
+      attributes: {
+        "id": "root",
+        "class": "root",
+        "hidden": "true"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    let svg = createSVGNode(this.win, {
+      nodeType: "svg",
+      parent: root,
+      attributes: {
+        "id": "elements",
+        "width": "100%",
+        "height": "100%"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    // Offset parent node highlighter.
+    createSVGNode(this.win, {
+      nodeType: "polygon",
+      parent: svg,
+      attributes: {
+        "class": "offset-parent",
+        "id": "offset-parent",
+        "hidden": "true"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    // Current node highlighter (margin box).
+    createSVGNode(this.win, {
+      nodeType: "polygon",
+      parent: svg,
+      attributes: {
+        "class": "current-node",
+        "id": "current-node",
+        "hidden": "true"
+      },
+      prefix: this.ID_CLASS_PREFIX
+    });
+
+    // Build the 4 side arrows, handlers and labels.
+    for (let name of GeoProp.SIDES) {
+      createSVGNode(this.win, {
+        nodeType: "line",
+        parent: svg,
+        attributes: {
+          "class": "arrow " + name,
+          "id": "arrow-" + name,
+          "hidden": "true"
+        },
+        prefix: this.ID_CLASS_PREFIX
+      });
+
+      createSVGNode(this.win, {
+        nodeType: "circle",
+        parent: svg,
+        attributes: {
+          "class": "handler-" + name,
+          "id": "handler-" + name,
+          "r": "4",
+          "data-side": name,
+          "hidden": "true"
+        },
+        prefix: this.ID_CLASS_PREFIX
+      });
+
+      // Labels are positioned by using a translated <g>. This group contains
+      // a path and text that are themselves positioned using another translated
+      // <g>. This is so that the label arrow points at the 0,0 coordinates of
+      // parent <g>.
+      let labelG = createSVGNode(this.win, {
+        nodeType: "g",
+        parent: svg,
+        attributes: {
+          "id": "label-" + name,
+          "hidden": "true"
+        },
+        prefix: this.ID_CLASS_PREFIX
+      });
+
+      let subG = createSVGNode(this.win, {
+        nodeType: "g",
+        parent: labelG,
+        attributes: {
+          "transform": GeoProp.isHorizontal(name)
+                       ? "translate(-30 -30)"
+                       : "translate(5 -10)"
+        }
+      });
+
+      createSVGNode(this.win, {
+        nodeType: "path",
+        parent: subG,
+        attributes: {
+          "class": "label-bubble",
+          "d": GeoProp.isHorizontal(name)
+               ? "M0 0 L60 0 L60 20 L35 20 L30 25 L25 20 L0 20z"
+               : "M5 0 L65 0 L65 20 L5 20 L5 15 L0 10 L5 5z"
+        },
+        prefix: this.ID_CLASS_PREFIX
+      });
+
+      createSVGNode(this.win, {
+        nodeType: "text",
+        parent: subG,
+        attributes: {
+          "class": "label-text",
+          "id": "label-text-" + name,
+          "x": GeoProp.isHorizontal(name) ? "30" : "35",
+          "y": "10"
+        },
+        prefix: this.ID_CLASS_PREFIX
+      });
+    }
+
+    return container;
+  },
+
+  destroy: function () {
+    // Avoiding exceptions if `destroy` is called multiple times; and / or the
+    // highlighter environment was already destroyed.
+    if (!this.highlighterEnv) {
+      return;
+    }
+
+    let { pageListenerTarget } = this.highlighterEnv;
+
+    DOM_EVENTS.forEach(type =>
+      pageListenerTarget.removeEventListener(type, this));
+
+    AutoRefreshHighlighter.prototype.destroy.call(this);
+
+    this.markup.destroy();
+    this.definedProperties.clear();
+    this.definedProperties = null;
+    this.offsetParent = null;
+  },
+
+  handleEvent: function (event, id) {
+    // No event handling if the highlighter is hidden
+    if (this.getElement("root").hasAttribute("hidden")) {
+      return;
+    }
+
+    const { type, pageX, pageY } = event;
+
+    switch (type) {
+      case "pagehide":
+        this.destroy();
+        break;
+      case "mousedown":
+        // The mousedown event is intended only for the handler
+        if (!id) {
+          return;
+        }
+
+        let handlerSide = this.markup.getElement(id).getAttribute("data-side");
+
+        if (handlerSide) {
+          let side = handlerSide;
+          let sideProp = this.definedProperties.get(side);
+
+          if (!sideProp) {
+            return;
+          }
+
+          let value = sideProp.cssRule.style.getPropertyValue(side);
+          let computedValue = this.computedStyle.getPropertyValue(side);
+
+          let [unit] = value.match(/[^\d]+$/) || [""];
+
+          value = parseFloat(value);
+
+          let ratio = (value / parseFloat(computedValue)) || 1;
+          let dir = GeoProp.isInverted(side) ? -1 : 1;
+
+          // Store all the initial values needed for drag & drop
+          this[_dragging] = {
+            side,
+            value,
+            unit,
+            x: pageX,
+            y: pageY,
+            inc: ratio * dir
+          };
+
+          this.getElement("handler-" + side).classList.add("dragging");
+        }
+
+        this.getElement("root").setAttribute("dragging", "true");
+        break;
+      case "mouseup":
+        // If we're dragging, drop it.
+        if (this[_dragging]) {
+          let { side } = this[_dragging];
+          this.getElement("root").removeAttribute("dragging");
+          this.getElement("handler-" + side).classList.remove("dragging");
+          this[_dragging] = null;
+        }
+        break;
+      case "mousemove":
+        if (!this[_dragging]) {
+          return;
+        }
+
+        let { side, x, y, value, unit, inc } = this[_dragging];
+        let sideProps = this.definedProperties.get(side);
+
+        if (!sideProps) {
+          return;
+        }
+
+        let delta = (GeoProp.isHorizontal(side) ? pageX - x : pageY - y) * inc;
+
+        // The inline style has usually the priority over any other CSS rule
+        // set in stylesheets. However, if a rule has `!important` keyword,
+        // it will override the inline style too. To ensure Geometry Editor
+        // will always update the element, we have to add `!important` as
+        // well.
+        this.currentNode.style.setProperty(
+          side, (value + delta) + unit, "important");
+
+        break;
+    }
+  },
+
+  getElement: function (id) {
+    return this.markup.getElement(this.ID_CLASS_PREFIX + id);
+  },
+
+  _show: function () {
+    this.computedStyle = getComputedStyle(this.currentNode);
+    let pos = this.computedStyle.position;
+    // XXX: sticky positioning is ignored for now. To be implemented next.
+    if (pos === "sticky") {
+      this.hide();
+      return false;
+    }
+
+    let hasUpdated = this._update();
+    if (!hasUpdated) {
+      this.hide();
+      return false;
+    }
+
+    this.getElement("root").removeAttribute("hidden");
+
+    return true;
+  },
+
+  _update: function () {
+    // At each update, the position or/and size may have changed, so get the
+    // list of defined properties, and re-position the arrows and highlighters.
+    this.definedProperties = getDefinedGeometryProperties(this.currentNode);
+
+    if (!this.definedProperties.size) {
+      console.warn("The element does not have editable geometry properties");
+      return false;
+    }
+
+    setIgnoreLayoutChanges(true);
+
+    // Update the highlighters and arrows.
+    this.updateOffsetParent();
+    this.updateCurrentNode();
+    this.updateArrows();
+
+    // Avoid zooming the arrows when content is zoomed.
+    let node = this.currentNode;
+    this.markup.scaleRootElement(node, this.ID_CLASS_PREFIX + "root");
+
+    setIgnoreLayoutChanges(false, node.ownerDocument.documentElement);
+    return true;
+  },
+
+  /**
+   * Update the offset parent rectangle.
+   * There are 3 different cases covered here:
+   * - the node is absolutely/fixed positioned, and an offsetParent is defined
+   *   (i.e. it's not just positioned in the viewport): the offsetParent node
+   *   is highlighted (i.e. the rectangle is shown),
+   * - the node is relatively positioned: the rectangle is shown where the node
+   *   would originally have been (because that's where the relative positioning
+   *   is calculated from),
+   * - the node has no offset parent at all: the offsetParent rectangle is
+   *   hidden.
+   */
+  updateOffsetParent: function () {
+    // Get the offsetParent, if any.
+    this.offsetParent = getOffsetParent(this.currentNode);
+    // And the offsetParent quads.
+    this.parentQuads = getAdjustedQuads(
+        this.win, this.offsetParent.element, "padding");
+
+    let el = this.getElement("offset-parent");
+
+    let isPositioned = this.computedStyle.position === "absolute" ||
+                       this.computedStyle.position === "fixed";
+    let isRelative = this.computedStyle.position === "relative";
+    let isHighlighted = false;
+
+    if (this.offsetParent.element && isPositioned) {
+      let {p1, p2, p3, p4} = this.parentQuads[0];
+      let points = p1.x + "," + p1.y + " " +
+                   p2.x + "," + p2.y + " " +
+                   p3.x + "," + p3.y + " " +
+                   p4.x + "," + p4.y;
+      el.setAttribute("points", points);
+      isHighlighted = true;
+    } else if (isRelative) {
+      let xDelta = parseFloat(this.computedStyle.left);
+      let yDelta = parseFloat(this.computedStyle.top);
+      if (xDelta || yDelta) {
+        let {p1, p2, p3, p4} = this.currentQuads.margin[0];
+        let points = (p1.x - xDelta) + "," + (p1.y - yDelta) + " " +
+                     (p2.x - xDelta) + "," + (p2.y - yDelta) + " " +
+                     (p3.x - xDelta) + "," + (p3.y - yDelta) + " " +
+                     (p4.x - xDelta) + "," + (p4.y - yDelta);
+        el.setAttribute("points", points);
+        isHighlighted = true;
+      }
+    }
+
+    if (isHighlighted) {
+      el.removeAttribute("hidden");
+    } else {
+      el.setAttribute("hidden", "true");
+    }
+  },
+
+  updateCurrentNode: function () {
+    let box = this.getElement("current-node");
+    let {p1, p2, p3, p4} = this.currentQuads.margin[0];
+    let attr = p1.x + "," + p1.y + " " +
+               p2.x + "," + p2.y + " " +
+               p3.x + "," + p3.y + " " +
+               p4.x + "," + p4.y;
+    box.setAttribute("points", attr);
+    box.removeAttribute("hidden");
+  },
+
+  _hide: function () {
+    setIgnoreLayoutChanges(true);
+
+    this.getElement("root").setAttribute("hidden", "true");
+    this.getElement("current-node").setAttribute("hidden", "true");
+    this.getElement("offset-parent").setAttribute("hidden", "true");
+    this.hideArrows();
+
+    this.definedProperties.clear();
+
+    setIgnoreLayoutChanges(false,
+      this.currentNode.ownerDocument.documentElement);
+  },
+
+  hideArrows: function () {
+    for (let side of GeoProp.SIDES) {
+      this.getElement("arrow-" + side).setAttribute("hidden", "true");
+      this.getElement("label-" + side).setAttribute("hidden", "true");
+      this.getElement("handler-" + side).setAttribute("hidden", "true");
+    }
+  },
+
+  updateArrows: function () {
+    this.hideArrows();
+
+    // Position arrows always end at the node's margin box.
+    let marginBox = this.currentQuads.margin[0].bounds;
+
+    // Position the side arrows which need to be visible.
+    // Arrows always start at the offsetParent edge, and end at the middle
+    // position of the node's margin edge.
+    // Note that for relative positioning, the offsetParent is considered to be
+    // the node itself, where it would have been originally.
+    // +------------------+----------------+
+    // | offsetparent     | top            |
+    // | or viewport      |                |
+    // |         +--------+--------+       |
+    // |         | node            |       |
+    // +---------+                 +-------+
+    // | left    |                 | right |
+    // |         +--------+--------+       |
+    // |                  | bottom         |
+    // +------------------+----------------+
+    let getSideArrowStartPos = side => {
+      // In case an offsetParent exists and is highlighted.
+      if (this.parentQuads && this.parentQuads.length) {
+        return this.parentQuads[0].bounds[side];
+      }
+
+      // In case of relative positioning.
+      if (this.computedStyle.position === "relative") {
+        if (GeoProp.isInverted(side)) {
+          return marginBox[side] + parseFloat(this.computedStyle[side]);
+        }
+        return marginBox[side] - parseFloat(this.computedStyle[side]);
+      }
+
+      // In case the element is positioned in the viewport.
+      if (GeoProp.isInverted(side)) {
+        return this.offsetParent.dimension[GeoProp.mainAxisSize(side)];
+      }
+      return -1 * this.currentNode.ownerDocument.defaultView["scroll" +
+                                              GeoProp.axis(side).toUpperCase()];
+    };
+
+    for (let side of GeoProp.SIDES) {
+      let sideProp = this.definedProperties.get(side);
+      if (!sideProp) {
+        continue;
+      }
+
+      let mainAxisStartPos = getSideArrowStartPos(side);
+      let mainAxisEndPos = marginBox[side];
+      let crossAxisPos = marginBox[GeoProp.crossAxisStart(side)] +
+                         marginBox[GeoProp.crossAxisSize(side)] / 2;
+
+      this.updateArrow(side, mainAxisStartPos, mainAxisEndPos, crossAxisPos,
+                       sideProp.cssRule.style.getPropertyValue(side));
+    }
+  },
+
+  updateArrow: function (side, mainStart, mainEnd, crossPos, labelValue) {
+    let arrowEl = this.getElement("arrow-" + side);
+    let labelEl = this.getElement("label-" + side);
+    let labelTextEl = this.getElement("label-text-" + side);
+    let handlerEl = this.getElement("handler-" + side);
+
+    // Position the arrow <line>.
+    arrowEl.setAttribute(GeoProp.axis(side) + "1", mainStart);
+    arrowEl.setAttribute(GeoProp.crossAxis(side) + "1", crossPos);
+    arrowEl.setAttribute(GeoProp.axis(side) + "2", mainEnd);
+    arrowEl.setAttribute(GeoProp.crossAxis(side) + "2", crossPos);
+    arrowEl.removeAttribute("hidden");
+
+    handlerEl.setAttribute("c" + GeoProp.axis(side), mainEnd);
+    handlerEl.setAttribute("c" + GeoProp.crossAxis(side), crossPos);
+    handlerEl.removeAttribute("hidden");
+
+    // Position the label <text> in the middle of the arrow (making sure it's
+    // not hidden below the fold).
+    let capitalize = str => str[0].toUpperCase() + str.substring(1);
+    let winMain = this.win["inner" + capitalize(GeoProp.mainAxisSize(side))];
+    let labelMain = mainStart + (mainEnd - mainStart) / 2;
+    if ((mainStart > 0 && mainStart < winMain) ||
+        (mainEnd > 0 && mainEnd < winMain)) {
+      if (labelMain < GEOMETRY_LABEL_SIZE) {
+        labelMain = GEOMETRY_LABEL_SIZE;
+      } else if (labelMain > winMain - GEOMETRY_LABEL_SIZE) {
+        labelMain = winMain - GEOMETRY_LABEL_SIZE;
+      }
+    }
+    let labelCross = crossPos;
+    labelEl.setAttribute("transform", GeoProp.isHorizontal(side)
+                         ? "translate(" + labelMain + " " + labelCross + ")"
+                         : "translate(" + labelCross + " " + labelMain + ")");
+    labelEl.removeAttribute("hidden");
+    labelTextEl.setTextContent(labelValue);
+  }
+});
+exports.GeometryEditorHighlighter = GeometryEditorHighlighter;
diff --git a/devtools/server/actors/highlighters/measuring-tool.js b/devtools/server/actors/highlighters/measuring-tool.js
new file mode 100644
index 000000000..e1e1de94f
--- /dev/null
+++ b/devtools/server/actors/highlighters/measuring-tool.js
@@ -0,0 +1,563 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const events = require("sdk/event/core");
+const { getCurrentZoom,
+  setIgnoreLayoutChanges } = require("devtools/shared/layout/utils");
+const {
+  CanvasFrameAnonymousContentHelper,
+  createSVGNode, createNode } = require("./utils/markup");
+
+// Hard coded value about the size of measuring tool label, in order to
+// position and flip it when is needed.
+const LABEL_SIZE_MARGIN = 8;
+const LABEL_SIZE_WIDTH = 80;
+const LABEL_SIZE_HEIGHT = 52;
+const LABEL_POS_MARGIN = 4;
+const LABEL_POS_WIDTH = 40;
+const LABEL_POS_HEIGHT = 34;
+
+const SIDES = ["top", "right", "bottom", "left"];
+
+/**
+ * The MeasuringToolHighlighter is used to measure distances in a content page.
+ * It allows users to click and drag with their mouse to draw an area whose
+ * dimensions will be displayed in a tooltip next to it.
+ * This allows users to measure distances between elements on a page.
+ */
+function MeasuringToolHighlighter(highlighterEnv) {
+  this.env = highlighterEnv;
+  this.markup = new CanvasFrameAnonymousContentHelper(highlighterEnv,
+    this._buildMarkup.bind(this));
+
+  this.coords = {
+    x: 0,
+    y: 0
+  };
+
+  let { pageListenerTarget } = highlighterEnv;
+
+  pageListenerTarget.addEventListener("mousedown", this);
+  pageListenerTarget.addEventListener("mousemove", this);
+  pageListenerTarget.addEventListener("mouseleave", this);
+  pageListenerTarget.addEventListener("scroll", this);
+  pageListenerTarget.addEventListener("pagehide", this);
+}
+
+MeasuringToolHighlighter.prototype = {
+  typeName: "MeasuringToolHighlighter",
+
+  ID_CLASS_PREFIX: "measuring-tool-highlighter-",
+
+  _buildMarkup() {
+    let prefix = this.ID_CLASS_PREFIX;
+    let { window } = this.env;
+
+    let container = createNode(window, {
+      attributes: {"class": "highlighter-container"}
+    });
+
+    let root = createNode(window, {
+      parent: container,
+      attributes: {
+        "id": "root",
+        "class": "root",
+      },
+      prefix
+    });
+
+    let svg = createSVGNode(window, {
+      nodeType: "svg",
+      parent: root,
+      attributes: {
+        id: "elements",
+        "class": "elements",
+        width: "100%",
+        height: "100%",
+        hidden: "true"
+      },
+      prefix
+    });
+
+    createNode(window, {
+      nodeType: "label",
+      attributes: {
+        id: "label-size",
+        "class": "label-size",
+        "hidden": "true"
+      },
+      parent: root,
+      prefix
+    });
+
+    createNode(window, {
+      nodeType: "label",
+      attributes: {
+        id: "label-position",
+        "class": "label-position",
+        "hidden": "true"
+      },
+      parent: root,
+      prefix
+    });
+
+    // Creating a <g> element in order to group all the paths below, that
+    // together represent the measuring tool; so that would be easier move them
+    // around
+    let g = createSVGNode(window, {
+      nodeType: "g",
+      attributes: {
+        id: "tool",
+      },
+      parent: svg,
+      prefix
+    });
+
+    createSVGNode(window, {
+      nodeType: "path",
+      attributes: {
+        id: "box-path"
+      },
+      parent: g,
+      prefix
+    });
+
+    createSVGNode(window, {
+      nodeType: "path",
+      attributes: {
+        id: "diagonal-path"
+      },
+      parent: g,
+      prefix
+    });
+
+    for (let side of SIDES) {
+      createSVGNode(window, {
+        nodeType: "line",
+        parent: svg,
+        attributes: {
+          "class": `guide-${side}`,
+          id: `guide-${side}`,
+          hidden: "true"
+        },
+        prefix
+      });
+    }
+
+    return container;
+  },
+
+  _update() {
+    let { window } = this.env;
+
+    setIgnoreLayoutChanges(true);
+
+    let zoom = getCurrentZoom(window);
+
+    let { documentElement } = window.document;
+
+    let width = Math.max(documentElement.clientWidth,
+                         documentElement.scrollWidth,
+                         documentElement.offsetWidth);
+
+    let height = Math.max(documentElement.clientHeight,
+                          documentElement.scrollHeight,
+                          documentElement.offsetHeight);
+
+    let { body } = window.document;
+
+    // get the size of the content document despite the compatMode
+    if (body) {
+      width = Math.max(width, body.scrollWidth, body.offsetWidth);
+      height = Math.max(height, body.scrollHeight, body.offsetHeight);
+    }
+
+    let { coords } = this;
+
+    let isZoomChanged = zoom !== coords.zoom;
+
+    if (isZoomChanged) {
+      coords.zoom = zoom;
+      this.updateLabel();
+    }
+
+    let isDocumentSizeChanged = width !== coords.documentWidth ||
+                                height !== coords.documentHeight;
+
+    if (isDocumentSizeChanged) {
+      coords.documentWidth = width;
+      coords.documentHeight = height;
+    }
+
+    // If either the document's size or the zoom is changed since the last
+    // repaint, we update the tool's size as well.
+    if (isZoomChanged || isDocumentSizeChanged) {
+      this.updateViewport();
+    }
+
+    setIgnoreLayoutChanges(false, documentElement);
+
+    this._rafID = window.requestAnimationFrame(() => this._update());
+  },
+
+  _cancelUpdate() {
+    if (this._rafID) {
+      this.env.window.cancelAnimationFrame(this._rafID);
+      this._rafID = 0;
+    }
+  },
+
+  destroy() {
+    this.hide();
+
+    this._cancelUpdate();
+
+    let { pageListenerTarget } = this.env;
+
+    pageListenerTarget.removeEventListener("mousedown", this);
+    pageListenerTarget.removeEventListener("mousemove", this);
+    pageListenerTarget.removeEventListener("mouseup", this);
+    pageListenerTarget.removeEventListener("scroll", this);
+    pageListenerTarget.removeEventListener("pagehide", this);
+    pageListenerTarget.removeEventListener("mouseleave", this);
+
+    this.markup.destroy();
+
+    events.emit(this, "destroy");
+  },
+
+  show() {
+    setIgnoreLayoutChanges(true);
+
+    this.getElement("elements").removeAttribute("hidden");
+
+    this._update();
+
+    setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+  },
+
+  hide() {
+    setIgnoreLayoutChanges(true);
+
+    this.hideLabel("size");
+    this.hideLabel("position");
+
+    this.getElement("elements").setAttribute("hidden", "true");
+
+    this._cancelUpdate();
+
+    setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+  },
+
+  getElement(id) {
+    return this.markup.getElement(this.ID_CLASS_PREFIX + id);
+  },
+
+  setSize(w, h) {
+    this.setCoords(undefined, undefined, w, h);
+  },
+
+  setCoords(x, y, w, h) {
+    let { coords } = this;
+
+    if (typeof x !== "undefined") {
+      coords.x = x;
+    }
+
+    if (typeof y !== "undefined") {
+      coords.y = y;
+    }
+
+    if (typeof w !== "undefined") {
+      coords.w = w;
+    }
+
+    if (typeof h !== "undefined") {
+      coords.h = h;
+    }
+
+    setIgnoreLayoutChanges(true);
+
+    if (this._isDragging) {
+      this.updatePaths();
+    }
+
+    this.updateLabel();
+
+    setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+  },
+
+  updatePaths() {
+    let { x, y, w, h } = this.coords;
+    let dir = `M0 0 L${w} 0 L${w} ${h} L0 ${h}z`;
+
+    // Adding correction to the line path, otherwise some pixels are drawn
+    // outside the main rectangle area.
+    let x1 = w > 0 ? 0.5 : 0;
+    let y1 = w < 0 && h < 0 ? -0.5 : 0;
+    let w1 = w + (h < 0 && w < 0 ? 0.5 : 0);
+    let h1 = h + (h > 0 && w > 0 ? -0.5 : 0);
+
+    let linedir = `M${x1} ${y1} L${w1} ${h1}`;
+
+    this.getElement("box-path").setAttribute("d", dir);
+    this.getElement("diagonal-path").setAttribute("d", linedir);
+    this.getElement("tool").setAttribute("transform", `translate(${x},${y})`);
+  },
+
+  updateLabel(type) {
+    type = type || this._isDragging ? "size" : "position";
+
+    let isSizeLabel = type === "size";
+
+    let label = this.getElement(`label-${type}`);
+
+    let origin = "top left";
+
+    let { innerWidth, innerHeight, scrollX, scrollY } = this.env.window;
+    let { x, y, w, h, zoom } = this.coords;
+    let scale = 1 / zoom;
+
+    w = w || 0;
+    h = h || 0;
+    x = (x || 0) + w;
+    y = (y || 0) + h;
+
+    let labelMargin, labelHeight, labelWidth;
+
+    if (isSizeLabel) {
+      labelMargin = LABEL_SIZE_MARGIN;
+      labelWidth = LABEL_SIZE_WIDTH;
+      labelHeight = LABEL_SIZE_HEIGHT;
+
+      let d = Math.hypot(w, h).toFixed(2);
+
+      label.setTextContent(`W: ${Math.abs(w)} px
+                            H: ${Math.abs(h)} px
+                            ↘: ${d}px`);
+    } else {
+      labelMargin = LABEL_POS_MARGIN;
+      labelWidth = LABEL_POS_WIDTH;
+      labelHeight = LABEL_POS_HEIGHT;
+
+      label.setTextContent(`${x}
+                            ${y}`);
+    }
+
+    // Size used to position properly the label
+    let labelBoxWidth = (labelWidth + labelMargin) * scale;
+    let labelBoxHeight = (labelHeight + labelMargin) * scale;
+
+    let isGoingLeft = w < scrollX;
+    let isSizeGoingLeft = isSizeLabel && isGoingLeft;
+    let isExceedingLeftMargin = x - labelBoxWidth < scrollX;
+    let isExceedingRightMargin = x + labelBoxWidth > innerWidth + scrollX;
+    let isExceedingTopMargin = y - labelBoxHeight < scrollY;
+    let isExceedingBottomMargin = y + labelBoxHeight > innerHeight + scrollY;
+
+    if ((isSizeGoingLeft && !isExceedingLeftMargin) || isExceedingRightMargin) {
+      x -= labelBoxWidth;
+      origin = "top right";
+    } else {
+      x += labelMargin * scale;
+    }
+
+    if (isSizeLabel) {
+      y += isExceedingTopMargin ? labelMargin * scale : -labelBoxHeight;
+    } else {
+      y += isExceedingBottomMargin ? -labelBoxHeight : labelMargin * scale;
+    }
+
+    label.setAttribute("style", `
+      width: ${labelWidth}px;
+      height: ${labelHeight}px;
+      transform-origin: ${origin};
+      transform: translate(${x}px,${y}px) scale(${scale})
+    `);
+
+    if (!isSizeLabel) {
+      let labelSize = this.getElement("label-size");
+      let style = labelSize.getAttribute("style");
+
+      if (style) {
+        labelSize.setAttribute("style",
+          style.replace(/scale[^)]+\)/, `scale(${scale})`));
+      }
+    }
+  },
+
+  updateViewport() {
+    let { scrollX, scrollY, devicePixelRatio } = this.env.window;
+    let { documentWidth, documentHeight, zoom } = this.coords;
+
+    // Because `devicePixelRatio` is affected by zoom (see bug 809788),
+    // in order to get the "real" device pixel ratio, we need divide by `zoom`
+    let pixelRatio = devicePixelRatio / zoom;
+
+    // The "real" device pixel ratio is used to calculate the max stroke
+    // width we can actually assign: on retina, for instance, it would be 0.5,
+    // where on non high dpi monitor would be 1.
+    let minWidth = 1 / pixelRatio;
+    let strokeWidth = Math.min(minWidth, minWidth / zoom);
+
+    this.getElement("root").setAttribute("style",
+      `stroke-width:${strokeWidth};
+       width:${documentWidth}px;
+       height:${documentHeight}px;
+       transform: translate(${-scrollX}px,${-scrollY}px)`);
+  },
+
+  updateGuides() {
+    let { x, y, w, h } = this.coords;
+
+    let guide = this.getElement("guide-top");
+
+    guide.setAttribute("x1", "0");
+    guide.setAttribute("y1", y);
+    guide.setAttribute("x2", "100%");
+    guide.setAttribute("y2", y);
+
+    guide = this.getElement("guide-right");
+
+    guide.setAttribute("x1", x + w);
+    guide.setAttribute("y1", 0);
+    guide.setAttribute("x2", x + w);
+    guide.setAttribute("y2", "100%");
+
+    guide = this.getElement("guide-bottom");
+
+    guide.setAttribute("x1", "0");
+    guide.setAttribute("y1", y + h);
+    guide.setAttribute("x2", "100%");
+    guide.setAttribute("y2", y + h);
+
+    guide = this.getElement("guide-left");
+
+    guide.setAttribute("x1", x);
+    guide.setAttribute("y1", 0);
+    guide.setAttribute("x2", x);
+    guide.setAttribute("y2", "100%");
+  },
+
+  showLabel(type) {
+    setIgnoreLayoutChanges(true);
+
+    this.getElement(`label-${type}`).removeAttribute("hidden");
+
+    setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+  },
+
+  hideLabel(type) {
+    setIgnoreLayoutChanges(true);
+
+    this.getElement(`label-${type}`).setAttribute("hidden", "true");
+
+    setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+  },
+
+  showGuides() {
+    let prefix = this.ID_CLASS_PREFIX + "guide-";
+
+    for (let side of SIDES) {
+      this.markup.removeAttributeForElement(`${prefix + side}`, "hidden");
+    }
+  },
+
+  hideGuides() {
+    let prefix = this.ID_CLASS_PREFIX + "guide-";
+
+    for (let side of SIDES) {
+      this.markup.setAttributeForElement(`${prefix + side}`, "hidden", "true");
+    }
+  },
+
+  handleEvent(event) {
+    let scrollX, scrollY, innerWidth, innerHeight;
+    let x, y;
+
+    let { pageListenerTarget } = this.env;
+
+    switch (event.type) {
+      case "mousedown":
+        if (event.button) {
+          return;
+        }
+
+        this._isDragging = true;
+
+        let { window } = this.env;
+
+        ({ scrollX, scrollY } = window);
+        x = event.clientX + scrollX;
+        y = event.clientY + scrollY;
+
+        pageListenerTarget.addEventListener("mouseup", this);
+
+        setIgnoreLayoutChanges(true);
+
+        this.getElement("tool").setAttribute("class", "dragging");
+
+        this.hideLabel("size");
+        this.hideLabel("position");
+
+        this.hideGuides();
+        this.setCoords(x, y, 0, 0);
+
+        setIgnoreLayoutChanges(false, window.document.documentElement);
+
+        break;
+      case "mouseup":
+        this._isDragging = false;
+
+        pageListenerTarget.removeEventListener("mouseup", this);
+
+        setIgnoreLayoutChanges(true);
+
+        this.getElement("tool").removeAttribute("class", "");
+
+        // Shows the guides only if an actual area is selected
+        if (this.coords.w !== 0 && this.coords.h !== 0) {
+          this.updateGuides();
+          this.showGuides();
+        }
+
+        setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+
+        break;
+      case "mousemove":
+        ({ scrollX, scrollY, innerWidth, innerHeight } = this.env.window);
+        x = event.clientX + scrollX;
+        y = event.clientY + scrollY;
+
+        let { coords } = this;
+
+        x = Math.min(innerWidth + scrollX - 1, Math.max(0 + scrollX, x));
+        y = Math.min(innerHeight + scrollY, Math.max(1 + scrollY, y));
+
+        this.setSize(x - coords.x, y - coords.y);
+
+        let type = this._isDragging ? "size" : "position";
+
+        this.showLabel(type);
+        break;
+      case "mouseleave":
+        if (!this._isDragging) {
+          this.hideLabel("position");
+        }
+        break;
+      case "scroll":
+        setIgnoreLayoutChanges(true);
+        this.updateViewport();
+        setIgnoreLayoutChanges(false, this.env.window.document.documentElement);
+
+        break;
+      case "pagehide":
+        this.destroy();
+        break;
+    }
+  }
+};
+exports.MeasuringToolHighlighter = MeasuringToolHighlighter;
diff --git a/devtools/server/actors/highlighters/moz.build b/devtools/server/actors/highlighters/moz.build
new file mode 100644
index 000000000..317d0832c
--- /dev/null
+++ b/devtools/server/actors/highlighters/moz.build
@@ -0,0 +1,23 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIRS += [
+    'utils',
+]
+
+DevToolsModules(
+    'auto-refresh.js',
+    'box-model.js',
+    'css-grid.js',
+    'css-transform.js',
+    'eye-dropper.js',
+    'geometry-editor.js',
+    'measuring-tool.js',
+    'rect.js',
+    'rulers.js',
+    'selector.js',
+    'simple-outline.js'
+)
diff --git a/devtools/server/actors/highlighters/rect.js b/devtools/server/actors/highlighters/rect.js
new file mode 100644
index 000000000..69ff09880
--- /dev/null
+++ b/devtools/server/actors/highlighters/rect.js
@@ -0,0 +1,102 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { CanvasFrameAnonymousContentHelper } = require("./utils/markup");
+const { getAdjustedQuads } = require("devtools/shared/layout/utils");
+/**
+ * The RectHighlighter is a class that draws a rectangle highlighter at specific
+ * coordinates.
+ * It does *not* highlight DOM nodes, but rects.
+ * It also does *not* update dynamically, it only highlights a rect and remains
+ * there as long as it is shown.
+ */
+function RectHighlighter(highlighterEnv) {
+  this.win = highlighterEnv.window;
+  this.markup = new CanvasFrameAnonymousContentHelper(highlighterEnv,
+    this._buildMarkup.bind(this));
+}
+
+RectHighlighter.prototype = {
+  typeName: "RectHighlighter",
+
+  _buildMarkup: function () {
+    let doc = this.win.document;
+
+    let container = doc.createElement("div");
+    container.className = "highlighter-container";
+    container.innerHTML = "<div id=\"highlighted-rect\" " +
+                          "class=\"highlighted-rect\" hidden=\"true\">";
+
+    return container;
+  },
+
+  destroy: function () {
+    this.win = null;
+    this.markup.destroy();
+  },
+
+  getElement: function (id) {
+    return this.markup.getElement(id);
+  },
+
+  _hasValidOptions: function (options) {
+    let isValidNb = n => typeof n === "number" && n >= 0 && isFinite(n);
+    return options && options.rect &&
+           isValidNb(options.rect.x) &&
+           isValidNb(options.rect.y) &&
+           options.rect.width && isValidNb(options.rect.width) &&
+           options.rect.height && isValidNb(options.rect.height);
+  },
+
+  /**
+   * @param {DOMNode} node The highlighter rect is relatively positioned to the
+   * viewport this node is in. Using the provided node, the highligther will get
+   * the parent documentElement and use it as context to position the
+   * highlighter correctly.
+   * @param {Object} options Accepts the following options:
+   * - rect: mandatory object that should have the x, y, width, height
+   *   properties
+   * - fill: optional fill color for the rect
+   */
+  show: function (node, options) {
+    if (!this._hasValidOptions(options) || !node || !node.ownerDocument) {
+      this.hide();
+      return false;
+    }
+
+    let contextNode = node.ownerDocument.documentElement;
+
+    // Caculate the absolute rect based on the context node's adjusted quads.
+    let quads = getAdjustedQuads(this.win, contextNode);
+    if (!quads.length) {
+      this.hide();
+      return false;
+    }
+
+    let {bounds} = quads[0];
+    let x = "left:" + (bounds.x + options.rect.x) + "px;";
+    let y = "top:" + (bounds.y + options.rect.y) + "px;";
+    let width = "width:" + options.rect.width + "px;";
+    let height = "height:" + options.rect.height + "px;";
+
+    let style = x + y + width + height;
+    if (options.fill) {
+      style += "background:" + options.fill + ";";
+    }
+
+    // Set the coordinates of the highlighter and show it
+    let rect = this.getElement("highlighted-rect");
+    rect.setAttribute("style", style);
+    rect.removeAttribute("hidden");
+
+    return true;
+  },
+
+  hide: function () {
+    this.getElement("highlighted-rect").setAttribute("hidden", "true");
+  }
+};
+exports.RectHighlighter = RectHighlighter;
diff --git a/devtools/server/actors/highlighters/rulers.js b/devtools/server/actors/highlighters/rulers.js
new file mode 100644
index 000000000..01e082e67
--- /dev/null
+++ b/devtools/server/actors/highlighters/rulers.js
@@ -0,0 +1,294 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const events = require("sdk/event/core");
+const { getCurrentZoom,
+  setIgnoreLayoutChanges } = require("devtools/shared/layout/utils");
+const {
+  CanvasFrameAnonymousContentHelper,
+  createSVGNode, createNode } = require("./utils/markup");
+
+// Maximum size, in pixel, for the horizontal ruler and vertical ruler
+// used by RulersHighlighter
+const RULERS_MAX_X_AXIS = 10000;
+const RULERS_MAX_Y_AXIS = 15000;
+// Number of steps after we add a graduation, marker and text in
+// RulersHighliter; currently the unit is in pixel.
+const RULERS_GRADUATION_STEP = 5;
+const RULERS_MARKER_STEP = 50;
+const RULERS_TEXT_STEP = 100;
+
+/**
+ * The RulersHighlighter is a class that displays both horizontal and
+ * vertical rules on the page, along the top and left edges, with pixel
+ * graduations, useful for users to quickly check distances
+ */
+function RulersHighlighter(highlighterEnv) {
+  this.env = highlighterEnv;
+  this.markup = new CanvasFrameAnonymousContentHelper(highlighterEnv,
+    this._buildMarkup.bind(this));
+
+  let { pageListenerTarget } = highlighterEnv;
+  pageListenerTarget.addEventListener("scroll", this);
+  pageListenerTarget.addEventListener("pagehide", this);
+}
+
+RulersHighlighter.prototype = {
+  typeName: "RulersHighlighter",
+
+  ID_CLASS_PREFIX: "rulers-highlighter-",
+
+  _buildMarkup: function () {
+    let { window } = this.env;
+    let prefix = this.ID_CLASS_PREFIX;
+
+    function createRuler(axis, size) {
+      let width, height;
+      let isHorizontal = true;
+
+      if (axis === "x") {
+        width = size;
+        height = 16;
+      } else if (axis === "y") {
+        width = 16;
+        height = size;
+        isHorizontal = false;
+      } else {
+        throw new Error(
+          `Invalid type of axis given; expected "x" or "y" but got "${axis}"`);
+      }
+
+      let g = createSVGNode(window, {
+        nodeType: "g",
+        attributes: {
+          id: `${axis}-axis`
+        },
+        parent: svg,
+        prefix
+      });
+
+      createSVGNode(window, {
+        nodeType: "rect",
+        attributes: {
+          y: isHorizontal ? 0 : 16,
+          width,
+          height
+        },
+        parent: g
+      });
+
+      let gRule = createSVGNode(window, {
+        nodeType: "g",
+        attributes: {
+          id: `${axis}-axis-ruler`
+        },
+        parent: g,
+        prefix
+      });
+
+      let pathGraduations = createSVGNode(window, {
+        nodeType: "path",
+        attributes: {
+          "class": "ruler-graduations",
+          width,
+          height
+        },
+        parent: gRule,
+        prefix
+      });
+
+      let pathMarkers = createSVGNode(window, {
+        nodeType: "path",
+        attributes: {
+          "class": "ruler-markers",
+          width,
+          height
+        },
+        parent: gRule,
+        prefix
+      });
+
+      let gText = createSVGNode(window, {
+        nodeType: "g",
+        attributes: {
+          id: `${axis}-axis-text`,
+          "class": (isHorizontal ? "horizontal" : "vertical") + "-labels"
+        },
+        parent: g,
+        prefix
+      });
+
+      let dGraduations = "";
+      let dMarkers = "";
+      let graduationLength;
+
+      for (let i = 0; i < size; i += RULERS_GRADUATION_STEP) {
+        if (i === 0) {
+          continue;
+        }
+
+        graduationLength = (i % 2 === 0) ? 6 : 4;
+
+        if (i % RULERS_TEXT_STEP === 0) {
+          graduationLength = 8;
+          createSVGNode(window, {
+            nodeType: "text",
+            parent: gText,
+            attributes: {
+              x: isHorizontal ? 2 + i : -i - 1,
+              y: 5
+            }
+          }).textContent = i;
+        }
+
+        if (isHorizontal) {
+          if (i % RULERS_MARKER_STEP === 0) {
+            dMarkers += `M${i} 0 L${i} ${graduationLength}`;
+          } else {
+            dGraduations += `M${i} 0 L${i} ${graduationLength} `;
+          }
+        } else {
+          if (i % 50 === 0) {
+            dMarkers += `M0 ${i} L${graduationLength} ${i}`;
+          } else {
+            dGraduations += `M0 ${i} L${graduationLength} ${i}`;
+          }
+        }
+      }
+
+      pathGraduations.setAttribute("d", dGraduations);
+      pathMarkers.setAttribute("d", dMarkers);
+
+      return g;
+    }
+
+    let container = createNode(window, {
+      attributes: {"class": "highlighter-container"}
+    });
+
+    let root = createNode(window, {
+      parent: container,
+      attributes: {
+        "id": "root",
+        "class": "root"
+      },
+      prefix
+    });
+
+    let svg = createSVGNode(window, {
+      nodeType: "svg",
+      parent: root,
+      attributes: {
+        id: "elements",
+        "class": "elements",
+        width: "100%",
+        height: "100%",
+        hidden: "true"
+      },
+      prefix
+    });
+
+    createRuler("x", RULERS_MAX_X_AXIS);
+    createRuler("y", RULERS_MAX_Y_AXIS);
+
+    return container;
+  },
+
+  handleEvent: function (event) {
+    switch (event.type) {
+      case "scroll":
+        this._onScroll(event);
+        break;
+      case "pagehide":
+        this.destroy();
+        break;
+    }
+  },
+
+  _onScroll: function (event) {
+    let prefix = this.ID_CLASS_PREFIX;
+    let { scrollX, scrollY } = event.view;
+
+    this.markup.getElement(`${prefix}x-axis-ruler`)
+                        .setAttribute("transform", `translate(${-scrollX})`);
+    this.markup.getElement(`${prefix}x-axis-text`)
+                        .setAttribute("transform", `translate(${-scrollX})`);
+    this.markup.getElement(`${prefix}y-axis-ruler`)
+                        .setAttribute("transform", `translate(0, ${-scrollY})`);
+    this.markup.getElement(`${prefix}y-axis-text`)
+                        .setAttribute("transform", `translate(0, ${-scrollY})`);
+  },
+
+  _update: function () {
+    let { window } = this.env;
+
+    setIgnoreLayoutChanges(true);
+
+    let zoom = getCurrentZoom(window);
+    let isZoomChanged = zoom !== this._zoom;
+
+    if (isZoomChanged) {
+      this._zoom = zoom;
+      this.updateViewport();
+    }
+
+    setIgnoreLayoutChanges(false, window.document.documentElement);
+
+    this._rafID = window.requestAnimationFrame(() => this._update());
+  },
+
+  _cancelUpdate: function () {
+    if (this._rafID) {
+      this.env.window.cancelAnimationFrame(this._rafID);
+      this._rafID = 0;
+    }
+  },
+  updateViewport: function () {
+    let { devicePixelRatio } = this.env.window;
+
+    // Because `devicePixelRatio` is affected by zoom (see bug 809788),
+    // in order to get the "real" device pixel ratio, we need divide by `zoom`
+    let pixelRatio = devicePixelRatio / this._zoom;
+
+    // The "real" device pixel ratio is used to calculate the max stroke
+    // width we can actually assign: on retina, for instance, it would be 0.5,
+    // where on non high dpi monitor would be 1.
+    let minWidth = 1 / pixelRatio;
+    let strokeWidth = Math.min(minWidth, minWidth / this._zoom);
+
+    this.markup.getElement(this.ID_CLASS_PREFIX + "root").setAttribute("style",
+      `stroke-width:${strokeWidth};`);
+  },
+
+  destroy: function () {
+    this.hide();
+
+    let { pageListenerTarget } = this.env;
+    pageListenerTarget.removeEventListener("scroll", this);
+    pageListenerTarget.removeEventListener("pagehide", this);
+
+    this.markup.destroy();
+
+    events.emit(this, "destroy");
+  },
+
+  show: function () {
+    this.markup.removeAttributeForElement(this.ID_CLASS_PREFIX + "elements",
+      "hidden");
+
+    this._update();
+
+    return true;
+  },
+
+  hide: function () {
+    this.markup.setAttributeForElement(this.ID_CLASS_PREFIX + "elements",
+      "hidden", "true");
+
+    this._cancelUpdate();
+  }
+};
+exports.RulersHighlighter = RulersHighlighter;
diff --git a/devtools/server/actors/highlighters/selector.js b/devtools/server/actors/highlighters/selector.js
new file mode 100644
index 000000000..557a6d541
--- /dev/null
+++ b/devtools/server/actors/highlighters/selector.js
@@ -0,0 +1,83 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { isNodeValid } = require("./utils/markup");
+const { BoxModelHighlighter } = require("./box-model");
+
+// How many maximum nodes can be highlighted at the same time by the
+// SelectorHighlighter
+const MAX_HIGHLIGHTED_ELEMENTS = 100;
+
+/**
+ * The SelectorHighlighter runs a given selector through querySelectorAll on the
+ * document of the provided context node and then uses the BoxModelHighlighter
+ * to highlight the matching nodes
+ */
+function SelectorHighlighter(highlighterEnv) {
+  this.highlighterEnv = highlighterEnv;
+  this._highlighters = [];
+}
+
+SelectorHighlighter.prototype = {
+  typeName: "SelectorHighlighter",
+
+  /**
+   * Show BoxModelHighlighter on each node that matches that provided selector.
+   * @param {DOMNode} node A context node that is used to get the document on
+   * which querySelectorAll should be executed. This node will NOT be
+   * highlighted.
+   * @param {Object} options Should at least contain the 'selector' option, a
+   * string that will be used in querySelectorAll. On top of this, all of the
+   * valid options to BoxModelHighlighter.show are also valid here.
+   */
+  show: function (node, options = {}) {
+    this.hide();
+
+    if (!isNodeValid(node) || !options.selector) {
+      return false;
+    }
+
+    let nodes = [];
+    try {
+      nodes = [...node.ownerDocument.querySelectorAll(options.selector)];
+    } catch (e) {
+      // It's fine if the provided selector is invalid, nodes will be an empty
+      // array.
+    }
+
+    delete options.selector;
+
+    let i = 0;
+    for (let matchingNode of nodes) {
+      if (i >= MAX_HIGHLIGHTED_ELEMENTS) {
+        break;
+      }
+
+      let highlighter = new BoxModelHighlighter(this.highlighterEnv);
+      if (options.fill) {
+        highlighter.regionFill[options.region || "border"] = options.fill;
+      }
+      highlighter.show(matchingNode, options);
+      this._highlighters.push(highlighter);
+      i++;
+    }
+
+    return true;
+  },
+
+  hide: function () {
+    for (let highlighter of this._highlighters) {
+      highlighter.destroy();
+    }
+    this._highlighters = [];
+  },
+
+  destroy: function () {
+    this.hide();
+    this.highlighterEnv = null;
+  }
+};
+exports.SelectorHighlighter = SelectorHighlighter;
diff --git a/devtools/server/actors/highlighters/simple-outline.js b/devtools/server/actors/highlighters/simple-outline.js
new file mode 100644
index 000000000..dae20f2d9
--- /dev/null
+++ b/devtools/server/actors/highlighters/simple-outline.js
@@ -0,0 +1,67 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {
+  installHelperSheet,
+  isNodeValid,
+  addPseudoClassLock,
+  removePseudoClassLock
+} = require("./utils/markup");
+
+// SimpleOutlineHighlighter's stylesheet
+const HIGHLIGHTED_PSEUDO_CLASS = ":-moz-devtools-highlighted";
+const SIMPLE_OUTLINE_SHEET = `.__fx-devtools-hide-shortcut__ {
+                                visibility: hidden !important
+                              }
+                              ${HIGHLIGHTED_PSEUDO_CLASS} {
+                                outline: 2px dashed #F06!important;
+                                outline-offset: -2px!important
+                              }`;
+/**
+ * The SimpleOutlineHighlighter is a class that has the same API than the
+ * BoxModelHighlighter, but adds a pseudo-class on the target element itself
+ * to draw a simple css outline around the element.
+ * It is used by the HighlighterActor when canvasframe-based highlighters can't
+ * be used. This is the case for XUL windows.
+ */
+function SimpleOutlineHighlighter(highlighterEnv) {
+  this.chromeDoc = highlighterEnv.document;
+}
+
+SimpleOutlineHighlighter.prototype = {
+  /**
+   * Destroy the nodes. Remove listeners.
+   */
+  destroy: function () {
+    this.hide();
+    this.chromeDoc = null;
+  },
+
+  /**
+   * Show the highlighter on a given node
+   * @param {DOMNode} node
+   */
+  show: function (node) {
+    if (isNodeValid(node) && (!this.currentNode || node !== this.currentNode)) {
+      this.hide();
+      this.currentNode = node;
+      installHelperSheet(node.ownerDocument.defaultView, SIMPLE_OUTLINE_SHEET);
+      addPseudoClassLock(node, HIGHLIGHTED_PSEUDO_CLASS);
+    }
+    return true;
+  },
+
+  /**
+   * Hide the highlighter, the outline and the infobar.
+   */
+  hide: function () {
+    if (this.currentNode) {
+      removePseudoClassLock(this.currentNode, HIGHLIGHTED_PSEUDO_CLASS);
+      this.currentNode = null;
+    }
+  }
+};
+exports.SimpleOutlineHighlighter = SimpleOutlineHighlighter;
diff --git a/devtools/server/actors/highlighters/utils/markup.js b/devtools/server/actors/highlighters/utils/markup.js
new file mode 100644
index 000000000..8750014bc
--- /dev/null
+++ b/devtools/server/actors/highlighters/utils/markup.js
@@ -0,0 +1,609 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cc, Ci, Cu } = require("chrome");
+const { getCurrentZoom,
+  getRootBindingParent } = require("devtools/shared/layout/utils");
+const { on, emit } = require("sdk/event/core");
+
+const lazyContainer = {};
+
+loader.lazyRequireGetter(lazyContainer, "CssLogic",
+  "devtools/server/css-logic", true);
+exports.getComputedStyle = (node) =>
+  lazyContainer.CssLogic.getComputedStyle(node);
+
+exports.getBindingElementAndPseudo = (node) =>
+  lazyContainer.CssLogic.getBindingElementAndPseudo(node);
+
+loader.lazyGetter(lazyContainer, "DOMUtils", () =>
+  Cc["@mozilla.org/inspector/dom-utils;1"].getService(Ci.inIDOMUtils));
+exports.hasPseudoClassLock = (...args) =>
+  lazyContainer.DOMUtils.hasPseudoClassLock(...args);
+
+exports.addPseudoClassLock = (...args) =>
+  lazyContainer.DOMUtils.addPseudoClassLock(...args);
+
+exports.removePseudoClassLock = (...args) =>
+  lazyContainer.DOMUtils.removePseudoClassLock(...args);
+
+exports.getCSSStyleRules = (...args) =>
+  lazyContainer.DOMUtils.getCSSStyleRules(...args);
+
+const SVG_NS = "http://www.w3.org/2000/svg";
+const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
+const STYLESHEET_URI = "resource://devtools/server/actors/" +
+                       "highlighters.css";
+// How high is the infobar (px).
+const INFOBAR_HEIGHT = 34;
+// What's the size of the infobar arrow (px).
+const INFOBAR_ARROW_SIZE = 9;
+
+const _tokens = Symbol("classList/tokens");
+
+/**
+ * Shims the element's `classList` for anonymous content elements; used
+ * internally by `CanvasFrameAnonymousContentHelper.getElement()` method.
+ */
+function ClassList(className) {
+  let trimmed = (className || "").trim();
+  this[_tokens] = trimmed ? trimmed.split(/\s+/) : [];
+}
+
+ClassList.prototype = {
+  item(index) {
+    return this[_tokens][index];
+  },
+  contains(token) {
+    return this[_tokens].includes(token);
+  },
+  add(token) {
+    if (!this.contains(token)) {
+      this[_tokens].push(token);
+    }
+    emit(this, "update");
+  },
+  remove(token) {
+    let index = this[_tokens].indexOf(token);
+
+    if (index > -1) {
+      this[_tokens].splice(index, 1);
+    }
+    emit(this, "update");
+  },
+  toggle(token) {
+    if (this.contains(token)) {
+      this.remove(token);
+    } else {
+      this.add(token);
+    }
+  },
+  get length() {
+    return this[_tokens].length;
+  },
+  [Symbol.iterator]: function* () {
+    for (let i = 0; i < this.tokens.length; i++) {
+      yield this[_tokens][i];
+    }
+  },
+  toString() {
+    return this[_tokens].join(" ");
+  }
+};
+
+/**
+ * Is this content window a XUL window?
+ * @param {Window} window
+ * @return {Boolean}
+ */
+function isXUL(window) {
+  return window.document.documentElement.namespaceURI === XUL_NS;
+}
+exports.isXUL = isXUL;
+
+/**
+ * Inject a helper stylesheet in the window.
+ */
+var installedHelperSheets = new WeakMap();
+
+function installHelperSheet(win, source, type = "agent") {
+  if (installedHelperSheets.has(win.document)) {
+    return;
+  }
+  let {Style} = require("sdk/stylesheet/style");
+  let {attach} = require("sdk/content/mod");
+  let style = Style({source, type});
+  attach(style, win);
+  installedHelperSheets.set(win.document, style);
+}
+exports.installHelperSheet = installHelperSheet;
+
+/**
+ * Returns true if a DOM node is "valid", where "valid" means that the node isn't a dead
+ * object wrapper, is still attached to a document, and is of a given type.
+ * @param {DOMNode} node
+ * @param {Number} nodeType Optional, defaults to ELEMENT_NODE
+ * @return {Boolean}
+ */
+function isNodeValid(node, nodeType = Ci.nsIDOMNode.ELEMENT_NODE) {
+  // Is it still alive?
+  if (!node || Cu.isDeadWrapper(node)) {
+    return false;
+  }
+
+  // Is it of the right type?
+  if (node.nodeType !== nodeType) {
+    return false;
+  }
+
+  // Is its document accessible?
+  let doc = node.ownerDocument;
+  if (!doc || !doc.defaultView) {
+    return false;
+  }
+
+  // Is the node connected to the document? Using getBindingParent adds
+  // support for anonymous elements generated by a node in the document.
+  let bindingParent = getRootBindingParent(node);
+  if (!doc.documentElement.contains(bindingParent)) {
+    return false;
+  }
+
+  return true;
+}
+exports.isNodeValid = isNodeValid;
+
+/**
+ * Helper function that creates SVG DOM nodes.
+ * @param {Window} This window's document will be used to create the element
+ * @param {Object} Options for the node include:
+ * - nodeType: the type of node, defaults to "box".
+ * - attributes: a {name:value} object to be used as attributes for the node.
+ * - prefix: a string that will be used to prefix the values of the id and class
+ *   attributes.
+ * - parent: if provided, the newly created element will be appended to this
+ *   node.
+ */
+function createSVGNode(win, options) {
+  if (!options.nodeType) {
+    options.nodeType = "box";
+  }
+  options.namespace = SVG_NS;
+  return createNode(win, options);
+}
+exports.createSVGNode = createSVGNode;
+
+/**
+ * Helper function that creates DOM nodes.
+ * @param {Window} This window's document will be used to create the element
+ * @param {Object} Options for the node include:
+ * - nodeType: the type of node, defaults to "div".
+ * - namespace: if passed, doc.createElementNS will be used instead of
+ *   doc.creatElement.
+ * - attributes: a {name:value} object to be used as attributes for the node.
+ * - prefix: a string that will be used to prefix the values of the id and class
+ *   attributes.
+ * - parent: if provided, the newly created element will be appended to this
+ *   node.
+ */
+function createNode(win, options) {
+  let type = options.nodeType || "div";
+
+  let node;
+  if (options.namespace) {
+    node = win.document.createElementNS(options.namespace, type);
+  } else {
+    node = win.document.createElement(type);
+  }
+
+  for (let name in options.attributes || {}) {
+    let value = options.attributes[name];
+    if (options.prefix && (name === "class" || name === "id")) {
+      value = options.prefix + value;
+    }
+    node.setAttribute(name, value);
+  }
+
+  if (options.parent) {
+    options.parent.appendChild(node);
+  }
+
+  return node;
+}
+exports.createNode = createNode;
+
+/**
+ * Every highlighters should insert their markup content into the document's
+ * canvasFrame anonymous content container (see dom/webidl/Document.webidl).
+ *
+ * Since this container gets cleared when the document navigates, highlighters
+ * should use this helper to have their markup content automatically re-inserted
+ * in the new document.
+ *
+ * Since the markup content is inserted in the canvasFrame using
+ * insertAnonymousContent, this means that it can be modified using the API
+ * described in AnonymousContent.webidl.
+ * To retrieve the AnonymousContent instance, use the content getter.
+ *
+ * @param {HighlighterEnv} highlighterEnv
+ *        The environemnt which windows will be used to insert the node.
+ * @param {Function} nodeBuilder
+ *        A function that, when executed, returns a DOM node to be inserted into
+ *        the canvasFrame.
+ */
+function CanvasFrameAnonymousContentHelper(highlighterEnv, nodeBuilder) {
+  this.highlighterEnv = highlighterEnv;
+  this.nodeBuilder = nodeBuilder;
+  this.anonymousContentDocument = this.highlighterEnv.document;
+  // XXX the next line is a wallpaper for bug 1123362.
+  this.anonymousContentGlobal = Cu.getGlobalForObject(
+                                this.anonymousContentDocument);
+
+  // Only try to create the highlighter when the document is loaded,
+  // otherwise, wait for the navigate event to fire.
+  let doc = this.highlighterEnv.document;
+  if (doc.documentElement && doc.readyState != "uninitialized") {
+    this._insert();
+  }
+
+  this._onNavigate = this._onNavigate.bind(this);
+  this.highlighterEnv.on("navigate", this._onNavigate);
+
+  this.listeners = new Map();
+}
+
+CanvasFrameAnonymousContentHelper.prototype = {
+  destroy: function () {
+    try {
+      let doc = this.anonymousContentDocument;
+      doc.removeAnonymousContent(this._content);
+    } catch (e) {
+      // If the current window isn't the one the content was inserted into, this
+      // will fail, but that's fine.
+    }
+    this.highlighterEnv.off("navigate", this._onNavigate);
+    this.highlighterEnv = this.nodeBuilder = this._content = null;
+    this.anonymousContentDocument = null;
+    this.anonymousContentGlobal = null;
+
+    this._removeAllListeners();
+  },
+
+  _insert: function () {
+    let doc = this.highlighterEnv.document;
+    // Insert the content node only if the document:
+    // * is loaded (navigate event will fire once it is),
+    // * still exists,
+    // * isn't in XUL.
+    if (doc.readyState == "uninitialized" ||
+        !doc.documentElement ||
+        isXUL(this.highlighterEnv.window)) {
+      return;
+    }
+
+    // For now highlighters.css is injected in content as a ua sheet because
+    // <style scoped> doesn't work inside anonymous content (see bug 1086532).
+    // If it did, highlighters.css would be injected as an anonymous content
+    // node using CanvasFrameAnonymousContentHelper instead.
+    installHelperSheet(this.highlighterEnv.window,
+      "@import url('" + STYLESHEET_URI + "');");
+    let node = this.nodeBuilder();
+
+    // It was stated that hidden documents don't accept
+    // `insertAnonymousContent` calls yet. That doesn't seems the case anymore,
+    // at least on desktop. Therefore, removing the code that was dealing with
+    // that scenario, fixes when we're adding anonymous content in a tab that
+    // is not the active one (see bug 1260043 and bug 1260044)
+    this._content = doc.insertAnonymousContent(node);
+  },
+
+  _onNavigate: function (e, {isTopLevel}) {
+    if (isTopLevel) {
+      this._removeAllListeners();
+      this._insert();
+      this.anonymousContentDocument = this.highlighterEnv.document;
+    }
+  },
+
+  getTextContentForElement: function (id) {
+    if (!this.content) {
+      return null;
+    }
+    return this.content.getTextContentForElement(id);
+  },
+
+  setTextContentForElement: function (id, text) {
+    if (this.content) {
+      this.content.setTextContentForElement(id, text);
+    }
+  },
+
+  setAttributeForElement: function (id, name, value) {
+    if (this.content) {
+      this.content.setAttributeForElement(id, name, value);
+    }
+  },
+
+  getAttributeForElement: function (id, name) {
+    if (!this.content) {
+      return null;
+    }
+    return this.content.getAttributeForElement(id, name);
+  },
+
+  removeAttributeForElement: function (id, name) {
+    if (this.content) {
+      this.content.removeAttributeForElement(id, name);
+    }
+  },
+
+  hasAttributeForElement: function (id, name) {
+    return typeof this.getAttributeForElement(id, name) === "string";
+  },
+
+  getCanvasContext: function (id, type = "2d") {
+    return this.content ? this.content.getCanvasContext(id, type) : null;
+  },
+
+  /**
+   * Add an event listener to one of the elements inserted in the canvasFrame
+   * native anonymous container.
+   * Like other methods in this helper, this requires the ID of the element to
+   * be passed in.
+   *
+   * Note that if the content page navigates, the event listeners won't be
+   * added again.
+   *
+   * Also note that unlike traditional DOM events, the events handled by
+   * listeners added here will propagate through the document only through
+   * bubbling phase, so the useCapture parameter isn't supported.
+   * It is possible however to call e.stopPropagation() to stop the bubbling.
+   *
+   * IMPORTANT: the chrome-only canvasFrame insertion API takes great care of
+   * not leaking references to inserted elements to chrome JS code. That's
+   * because otherwise, chrome JS code could freely modify native anon elements
+   * inside the canvasFrame and probably change things that are assumed not to
+   * change by the C++ code managing this frame.
+   * See https://wiki.mozilla.org/DevTools/Highlighter#The_AnonymousContent_API
+   * Unfortunately, the inserted nodes are still available via
+   * event.originalTarget, and that's what the event handler here uses to check
+   * that the event actually occured on the right element, but that also means
+   * consumers of this code would be able to access the inserted elements.
+   * Therefore, the originalTarget property will be nullified before the event
+   * is passed to your handler.
+   *
+   * IMPL DETAIL: A single event listener is added per event types only, at
+   * browser level and if the event originalTarget is found to have the provided
+   * ID, the callback is executed (and then IDs of parent nodes of the
+   * originalTarget are checked too).
+   *
+   * @param {String} id
+   * @param {String} type
+   * @param {Function} handler
+   */
+  addEventListenerForElement: function (id, type, handler) {
+    if (typeof id !== "string") {
+      throw new Error("Expected a string ID in addEventListenerForElement but" +
+        " got: " + id);
+    }
+
+    // If no one is listening for this type of event yet, add one listener.
+    if (!this.listeners.has(type)) {
+      let target = this.highlighterEnv.pageListenerTarget;
+      target.addEventListener(type, this, true);
+      // Each type entry in the map is a map of ids:handlers.
+      this.listeners.set(type, new Map());
+    }
+
+    let listeners = this.listeners.get(type);
+    listeners.set(id, handler);
+  },
+
+  /**
+   * Remove an event listener from one of the elements inserted in the
+   * canvasFrame native anonymous container.
+   * @param {String} id
+   * @param {String} type
+   */
+  removeEventListenerForElement: function (id, type) {
+    let listeners = this.listeners.get(type);
+    if (!listeners) {
+      return;
+    }
+    listeners.delete(id);
+
+    // If no one is listening for event type anymore, remove the listener.
+    if (!this.listeners.has(type)) {
+      let target = this.highlighterEnv.pageListenerTarget;
+      target.removeEventListener(type, this, true);
+    }
+  },
+
+  handleEvent: function (event) {
+    let listeners = this.listeners.get(event.type);
+    if (!listeners) {
+      return;
+    }
+
+    // Hide the originalTarget property to avoid exposing references to native
+    // anonymous elements. See addEventListenerForElement's comment.
+    let isPropagationStopped = false;
+    let eventProxy = new Proxy(event, {
+      get: (obj, name) => {
+        if (name === "originalTarget") {
+          return null;
+        } else if (name === "stopPropagation") {
+          return () => {
+            isPropagationStopped = true;
+          };
+        }
+        return obj[name];
+      }
+    });
+
+    // Start at originalTarget, bubble through ancestors and call handlers when
+    // needed.
+    let node = event.originalTarget;
+    while (node) {
+      let handler = listeners.get(node.id);
+      if (handler) {
+        handler(eventProxy, node.id);
+        if (isPropagationStopped) {
+          break;
+        }
+      }
+      node = node.parentNode;
+    }
+  },
+
+  _removeAllListeners: function () {
+    if (this.highlighterEnv) {
+      let target = this.highlighterEnv.pageListenerTarget;
+      for (let [type] of this.listeners) {
+        target.removeEventListener(type, this, true);
+      }
+    }
+    this.listeners.clear();
+  },
+
+  getElement: function (id) {
+    let classList = new ClassList(this.getAttributeForElement(id, "class"));
+
+    on(classList, "update", () => {
+      this.setAttributeForElement(id, "class", classList.toString());
+    });
+
+    return {
+      getTextContent: () => this.getTextContentForElement(id),
+      setTextContent: text => this.setTextContentForElement(id, text),
+      setAttribute: (name, val) => this.setAttributeForElement(id, name, val),
+      getAttribute: name => this.getAttributeForElement(id, name),
+      removeAttribute: name => this.removeAttributeForElement(id, name),
+      hasAttribute: name => this.hasAttributeForElement(id, name),
+      getCanvasContext: type => this.getCanvasContext(id, type),
+      addEventListener: (type, handler) => {
+        return this.addEventListenerForElement(id, type, handler);
+      },
+      removeEventListener: (type, handler) => {
+        return this.removeEventListenerForElement(id, type, handler);
+      },
+      classList
+    };
+  },
+
+  get content() {
+    if (!this._content || Cu.isDeadWrapper(this._content)) {
+      return null;
+    }
+    return this._content;
+  },
+
+  /**
+   * The canvasFrame anonymous content container gets zoomed in/out with the
+   * page. If this is unwanted, i.e. if you want the inserted element to remain
+   * unzoomed, then this method can be used.
+   *
+   * Consumers of the CanvasFrameAnonymousContentHelper should call this method,
+   * it isn't executed automatically. Typically, AutoRefreshHighlighter can call
+   * it when _update is executed.
+   *
+   * The matching element will be scaled down or up by 1/zoomLevel (using css
+   * transform) to cancel the current zoom. The element's width and height
+   * styles will also be set according to the scale. Finally, the element's
+   * position will be set as absolute.
+   *
+   * Note that if the matching element already has an inline style attribute, it
+   * *won't* be preserved.
+   *
+   * @param {DOMNode} node This node is used to determine which container window
+   * should be used to read the current zoom value.
+   * @param {String} id The ID of the root element inserted with this API.
+   */
+  scaleRootElement: function (node, id) {
+    let zoom = getCurrentZoom(node);
+    let value = "position:absolute;width:100%;height:100%;";
+
+    if (zoom !== 1) {
+      value = "position:absolute;";
+      value += "transform-origin:top left;transform:scale(" + (1 / zoom) + ");";
+      value += "width:" + (100 * zoom) + "%;height:" + (100 * zoom) + "%;";
+    }
+
+    this.setAttributeForElement(id, "style", value);
+  }
+};
+exports.CanvasFrameAnonymousContentHelper = CanvasFrameAnonymousContentHelper;
+
+/**
+ * Move the infobar to the right place in the highlighter. This helper method is utilized
+ * in both css-grid.js and box-model.js to help position the infobar in an appropriate
+ * space over the highlighted node element or grid area. The infobar is used to display
+ * relevant information about the highlighted item (ex, node or grid name and dimensions).
+ *
+ * This method will first try to position the infobar to top or bottom of the container
+ * such that it has enough space for the height of the infobar. Afterwards, it will try
+ * to horizontally center align with the container element if possible.
+ *
+ * @param  {DOMNode} container
+ *         The container element which will be used to position the infobar.
+ * @param  {Object} bounds
+ *         The content bounds of the container element.
+ * @param  {Window} win
+ *         The window object.
+ */
+function moveInfobar(container, bounds, win) {
+  let winHeight = win.innerHeight * getCurrentZoom(win);
+  let winWidth = win.innerWidth * getCurrentZoom(win);
+  let winScrollY = win.scrollY;
+
+  // Ensure that containerBottom and containerTop are at least zero to avoid
+  // showing tooltips outside the viewport.
+  let containerBottom = Math.max(0, bounds.bottom) + INFOBAR_ARROW_SIZE;
+  let containerTop = Math.min(winHeight, bounds.top);
+
+  // Can the bar be above the node?
+  let top;
+  if (containerTop < INFOBAR_HEIGHT) {
+    // No. Can we move the bar under the node?
+    if (containerBottom + INFOBAR_HEIGHT > winHeight) {
+      // No. Let's move it inside. Can we show it at the top of the element?
+      if (containerTop < winScrollY) {
+        // No. Window is scrolled past the top of the element.
+        top = 0;
+      } else {
+        // Yes. Show it at the top of the element
+        top = containerTop;
+      }
+      container.setAttribute("position", "overlap");
+    } else {
+      // Yes. Let's move it under the node.
+      top = containerBottom;
+      container.setAttribute("position", "bottom");
+    }
+  } else {
+    // Yes. Let's move it on top of the node.
+    top = containerTop - INFOBAR_HEIGHT;
+    container.setAttribute("position", "top");
+  }
+
+  // Align the bar with the box's center if possible.
+  let left = bounds.right - bounds.width / 2;
+  // Make sure the while infobar is visible.
+  let buffer = 100;
+  if (left < buffer) {
+    left = buffer;
+    container.setAttribute("hide-arrow", "true");
+  } else if (left > winWidth - buffer) {
+    left = winWidth - buffer;
+    container.setAttribute("hide-arrow", "true");
+  } else {
+    container.removeAttribute("hide-arrow");
+  }
+
+  let style = "top:" + top + "px;left:" + left + "px;";
+  container.setAttribute("style", style);
+}
+exports.moveInfobar = moveInfobar;
diff --git a/devtools/server/actors/highlighters/utils/moz.build b/devtools/server/actors/highlighters/utils/moz.build
new file mode 100644
index 000000000..4bb429bc3
--- /dev/null
+++ b/devtools/server/actors/highlighters/utils/moz.build
@@ -0,0 +1,9 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    'markup.js'
+)
diff --git a/devtools/server/actors/inspector.js b/devtools/server/actors/inspector.js
new file mode 100644
index 000000000..20a227a40
--- /dev/null
+++ b/devtools/server/actors/inspector.js
@@ -0,0 +1,3186 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * Here's the server side of the remote inspector.
+ *
+ * The WalkerActor is the client's view of the debuggee's DOM.  It's gives
+ * the client a tree of NodeActor objects.
+ *
+ * The walker presents the DOM tree mostly unmodified from the source DOM
+ * tree, but with a few key differences:
+ *
+ *  - Empty text nodes are ignored.  This is pretty typical of developer
+ *    tools, but maybe we should reconsider that on the server side.
+ *  - iframes with documents loaded have the loaded document as the child,
+ *    the walker provides one big tree for the whole document tree.
+ *
+ * There are a few ways to get references to NodeActors:
+ *
+ *   - When you first get a WalkerActor reference, it comes with a free
+ *     reference to the root document's node.
+ *   - Given a node, you can ask for children, siblings, and parents.
+ *   - You can issue querySelector and querySelectorAll requests to find
+ *     other elements.
+ *   - Requests that return arbitrary nodes from the tree (like querySelector
+ *     and querySelectorAll) will also return any nodes the client hasn't
+ *     seen in order to have a complete set of parents.
+ *
+ * Once you have a NodeFront, you should be able to answer a few questions
+ * without further round trips, like the node's name, namespace/tagName,
+ * attributes, etc.  Other questions (like a text node's full nodeValue)
+ * might require another round trip.
+ *
+ * The protocol guarantees that the client will always know the parent of
+ * any node that is returned by the server.  This means that some requests
+ * (like querySelector) will include the extra nodes needed to satisfy this
+ * requirement.  The client keeps track of this parent relationship, so the
+ * node fronts form a tree that is a subset of the actual DOM tree.
+ *
+ *
+ * We maintain this guarantee to support the ability to release subtrees on
+ * the client - when a node is disconnected from the DOM tree we want to be
+ * able to free the client objects for all the children nodes.
+ *
+ * So to be able to answer "all the children of a given node that we have
+ * seen on the client side", we guarantee that every time we've seen a node,
+ * we connect it up through its parents.
+ */
+
+const {Cc, Ci, Cu} = require("chrome");
+const Services = require("Services");
+const protocol = require("devtools/shared/protocol");
+const {LayoutActor} = require("devtools/server/actors/layout");
+const {LongStringActor} = require("devtools/server/actors/string");
+const promise = require("promise");
+const {Task} = require("devtools/shared/task");
+const events = require("sdk/event/core");
+const {WalkerSearch} = require("devtools/server/actors/utils/walker-search");
+const {PageStyleActor, getFontPreviewData} = require("devtools/server/actors/styles");
+const {
+  HighlighterActor,
+  CustomHighlighterActor,
+  isTypeRegistered,
+  HighlighterEnvironment
+} = require("devtools/server/actors/highlighters");
+const {EyeDropper} = require("devtools/server/actors/highlighters/eye-dropper");
+const {
+  isAnonymous,
+  isNativeAnonymous,
+  isXBLAnonymous,
+  isShadowAnonymous,
+  getFrameElement
+} = require("devtools/shared/layout/utils");
+const {getLayoutChangesObserver, releaseLayoutChangesObserver} = require("devtools/server/actors/reflow");
+const nodeFilterConstants = require("devtools/shared/dom-node-filter-constants");
+
+const {EventParsers} = require("devtools/server/event-parsers");
+const {nodeSpec, nodeListSpec, walkerSpec, inspectorSpec} = require("devtools/shared/specs/inspector");
+
+const FONT_FAMILY_PREVIEW_TEXT = "The quick brown fox jumps over the lazy dog";
+const FONT_FAMILY_PREVIEW_TEXT_SIZE = 20;
+const PSEUDO_CLASSES = [":hover", ":active", ":focus"];
+const HIDDEN_CLASS = "__fx-devtools-hide-shortcut__";
+const XHTML_NS = "http://www.w3.org/1999/xhtml";
+const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
+const IMAGE_FETCHING_TIMEOUT = 500;
+const RX_FUNC_NAME =
+  /((var|const|let)\s+)?([\w$.]+\s*[:=]\s*)*(function)?\s*\*?\s*([\w$]+)?\s*$/;
+
+// The possible completions to a ':' with added score to give certain values
+// some preference.
+const PSEUDO_SELECTORS = [
+  [":active", 1],
+  [":hover", 1],
+  [":focus", 1],
+  [":visited", 0],
+  [":link", 0],
+  [":first-letter", 0],
+  [":first-child", 2],
+  [":before", 2],
+  [":after", 2],
+  [":lang(", 0],
+  [":not(", 3],
+  [":first-of-type", 0],
+  [":last-of-type", 0],
+  [":only-of-type", 0],
+  [":only-child", 2],
+  [":nth-child(", 3],
+  [":nth-last-child(", 0],
+  [":nth-of-type(", 0],
+  [":nth-last-of-type(", 0],
+  [":last-child", 2],
+  [":root", 0],
+  [":empty", 0],
+  [":target", 0],
+  [":enabled", 0],
+  [":disabled", 0],
+  [":checked", 1],
+  ["::selection", 0]
+];
+
+var HELPER_SHEET = `
+  .__fx-devtools-hide-shortcut__ {
+    visibility: hidden !important;
+  }
+
+  :-moz-devtools-highlighted {
+    outline: 2px dashed #F06!important;
+    outline-offset: -2px !important;
+  }
+`;
+
+const flags = require("devtools/shared/flags");
+
+loader.lazyRequireGetter(this, "DevToolsUtils",
+                         "devtools/shared/DevToolsUtils");
+
+loader.lazyRequireGetter(this, "AsyncUtils", "devtools/shared/async-utils");
+
+loader.lazyGetter(this, "DOMParser", function () {
+  return Cc["@mozilla.org/xmlextras/domparser;1"]
+           .createInstance(Ci.nsIDOMParser);
+});
+
+loader.lazyGetter(this, "eventListenerService", function () {
+  return Cc["@mozilla.org/eventlistenerservice;1"]
+           .getService(Ci.nsIEventListenerService);
+});
+
+loader.lazyGetter(this, "CssLogic", () => require("devtools/server/css-logic").CssLogic);
+
+/**
+ * We only send nodeValue up to a certain size by default.  This stuff
+ * controls that size.
+ */
+exports.DEFAULT_VALUE_SUMMARY_LENGTH = 50;
+var gValueSummaryLength = exports.DEFAULT_VALUE_SUMMARY_LENGTH;
+
+exports.getValueSummaryLength = function () {
+  return gValueSummaryLength;
+};
+
+exports.setValueSummaryLength = function (val) {
+  gValueSummaryLength = val;
+};
+
+// When the user selects a node to inspect in e10s, the parent process
+// has a CPOW that wraps the node being inspected.  It uses the
+// message manager to send this node to the child, which stores the
+// node in gInspectingNode. Then a findInspectingNode request is sent
+// over the remote debugging protocol, and gInspectingNode is returned
+// to the parent as a NodeFront.
+var gInspectingNode = null;
+
+// We expect this function to be called from the child.js frame script
+// when it receives the node to be inspected over the message manager.
+exports.setInspectingNode = function (val) {
+  gInspectingNode = val;
+};
+
+/**
+ * Returns the properly cased version of the node's tag name, which can be
+ * used when displaying said name in the UI.
+ *
+ * @param  {Node} rawNode
+ *         Node for which we want the display name
+ * @return {String}
+ *         Properly cased version of the node tag name
+ */
+const getNodeDisplayName = function (rawNode) {
+  if (rawNode.nodeName && !rawNode.localName) {
+    // The localName & prefix APIs have been moved from the Node interface to the Element
+    // interface. Use Node.nodeName as a fallback.
+    return rawNode.nodeName;
+  }
+  return (rawNode.prefix ? rawNode.prefix + ":" : "") + rawNode.localName;
+};
+exports.getNodeDisplayName = getNodeDisplayName;
+
+/**
+ * Server side of the node actor.
+ */
+var NodeActor = exports.NodeActor = protocol.ActorClassWithSpec(nodeSpec, {
+  initialize: function (walker, node) {
+    protocol.Actor.prototype.initialize.call(this, null);
+    this.walker = walker;
+    this.rawNode = node;
+    this._eventParsers = new EventParsers().parsers;
+
+    // Storing the original display of the node, to track changes when reflows
+    // occur
+    this.wasDisplayed = this.isDisplayed;
+  },
+
+  toString: function () {
+    return "[NodeActor " + this.actorID + " for " +
+      this.rawNode.toString() + "]";
+  },
+
+  /**
+   * Instead of storing a connection object, the NodeActor gets its connection
+   * from its associated walker.
+   */
+  get conn() {
+    return this.walker.conn;
+  },
+
+  isDocumentElement: function () {
+    return this.rawNode.ownerDocument &&
+           this.rawNode.ownerDocument.documentElement === this.rawNode;
+  },
+
+  destroy: function () {
+    protocol.Actor.prototype.destroy.call(this);
+
+    if (this.mutationObserver) {
+      if (!Cu.isDeadWrapper(this.mutationObserver)) {
+        this.mutationObserver.disconnect();
+      }
+      this.mutationObserver = null;
+    }
+    this.rawNode = null;
+    this.walker = null;
+  },
+
+  // Returns the JSON representation of this object over the wire.
+  form: function (detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    let parentNode = this.walker.parentNode(this);
+    let inlineTextChild = this.walker.inlineTextChild(this);
+
+    let form = {
+      actor: this.actorID,
+      baseURI: this.rawNode.baseURI,
+      parent: parentNode ? parentNode.actorID : undefined,
+      nodeType: this.rawNode.nodeType,
+      namespaceURI: this.rawNode.namespaceURI,
+      nodeName: this.rawNode.nodeName,
+      nodeValue: this.rawNode.nodeValue,
+      displayName: getNodeDisplayName(this.rawNode),
+      numChildren: this.numChildren,
+      inlineTextChild: inlineTextChild ? inlineTextChild.form() : undefined,
+
+      // doctype attributes
+      name: this.rawNode.name,
+      publicId: this.rawNode.publicId,
+      systemId: this.rawNode.systemId,
+
+      attrs: this.writeAttrs(),
+      isBeforePseudoElement: this.isBeforePseudoElement,
+      isAfterPseudoElement: this.isAfterPseudoElement,
+      isAnonymous: isAnonymous(this.rawNode),
+      isNativeAnonymous: isNativeAnonymous(this.rawNode),
+      isXBLAnonymous: isXBLAnonymous(this.rawNode),
+      isShadowAnonymous: isShadowAnonymous(this.rawNode),
+      pseudoClassLocks: this.writePseudoClassLocks(),
+
+      isDisplayed: this.isDisplayed,
+      isInHTMLDocument: this.rawNode.ownerDocument &&
+        this.rawNode.ownerDocument.contentType === "text/html",
+      hasEventListeners: this._hasEventListeners,
+    };
+
+    if (this.isDocumentElement()) {
+      form.isDocumentElement = true;
+    }
+
+    // Add an extra API for custom properties added by other
+    // modules/extensions.
+    form.setFormProperty = (name, value) => {
+      if (!form.props) {
+        form.props = {};
+      }
+      form.props[name] = value;
+    };
+
+    // Fire an event so, other modules can create its own properties
+    // that should be passed to the client (within the form.props field).
+    events.emit(NodeActor, "form", {
+      target: this,
+      data: form
+    });
+
+    return form;
+  },
+
+  /**
+   * Watch the given document node for mutations using the DOM observer
+   * API.
+   */
+  watchDocument: function (callback) {
+    let node = this.rawNode;
+    // Create the observer on the node's actor.  The node will make sure
+    // the observer is cleaned up when the actor is released.
+    let observer = new node.defaultView.MutationObserver(callback);
+    observer.mergeAttributeRecords = true;
+    observer.observe(node, {
+      nativeAnonymousChildList: true,
+      attributes: true,
+      characterData: true,
+      characterDataOldValue: true,
+      childList: true,
+      subtree: true
+    });
+    this.mutationObserver = observer;
+  },
+
+  get isBeforePseudoElement() {
+    return this.rawNode.nodeName === "_moz_generated_content_before";
+  },
+
+  get isAfterPseudoElement() {
+    return this.rawNode.nodeName === "_moz_generated_content_after";
+  },
+
+  // Estimate the number of children that the walker will return without making
+  // a call to children() if possible.
+  get numChildren() {
+    // For pseudo elements, childNodes.length returns 1, but the walker
+    // will return 0.
+    if (this.isBeforePseudoElement || this.isAfterPseudoElement) {
+      return 0;
+    }
+
+    let rawNode = this.rawNode;
+    let numChildren = rawNode.childNodes.length;
+    let hasAnonChildren = rawNode.nodeType === Ci.nsIDOMNode.ELEMENT_NODE &&
+                          rawNode.ownerDocument.getAnonymousNodes(rawNode);
+
+    let hasContentDocument = rawNode.contentDocument;
+    let hasSVGDocument = rawNode.getSVGDocument && rawNode.getSVGDocument();
+    if (numChildren === 0 && (hasContentDocument || hasSVGDocument)) {
+      // This might be an iframe with virtual children.
+      numChildren = 1;
+    }
+
+    // Normal counting misses ::before/::after.  Also, some anonymous children
+    // may ultimately be skipped, so we have to consult with the walker.
+    if (numChildren === 0 || hasAnonChildren) {
+      numChildren = this.walker.children(this).nodes.length;
+    }
+
+    return numChildren;
+  },
+
+  get computedStyle() {
+    return CssLogic.getComputedStyle(this.rawNode);
+  },
+
+  /**
+   * Is the node's display computed style value other than "none"
+   */
+  get isDisplayed() {
+    // Consider all non-element nodes as displayed.
+    if (isNodeDead(this) ||
+        this.rawNode.nodeType !== Ci.nsIDOMNode.ELEMENT_NODE ||
+        this.isAfterPseudoElement ||
+        this.isBeforePseudoElement) {
+      return true;
+    }
+
+    let style = this.computedStyle;
+    if (!style) {
+      return true;
+    }
+
+    return style.display !== "none";
+  },
+
+  /**
+   * Are there event listeners that are listening on this node? This method
+   * uses all parsers registered via event-parsers.js.registerEventParser() to
+   * check if there are any event listeners.
+   */
+  get _hasEventListeners() {
+    let parsers = this._eventParsers;
+    for (let [, {hasListeners}] of parsers) {
+      try {
+        if (hasListeners && hasListeners(this.rawNode)) {
+          return true;
+        }
+      } catch (e) {
+        // An object attached to the node looked like a listener but wasn't...
+        // do nothing.
+      }
+    }
+    return false;
+  },
+
+  writeAttrs: function () {
+    if (!this.rawNode.attributes) {
+      return undefined;
+    }
+
+    return [...this.rawNode.attributes].map(attr => {
+      return {namespace: attr.namespace, name: attr.name, value: attr.value };
+    });
+  },
+
+  writePseudoClassLocks: function () {
+    if (this.rawNode.nodeType !== Ci.nsIDOMNode.ELEMENT_NODE) {
+      return undefined;
+    }
+    let ret = undefined;
+    for (let pseudo of PSEUDO_CLASSES) {
+      if (DOMUtils.hasPseudoClassLock(this.rawNode, pseudo)) {
+        ret = ret || [];
+        ret.push(pseudo);
+      }
+    }
+    return ret;
+  },
+
+  /**
+   * Gets event listeners and adds their information to the events array.
+   *
+   * @param  {Node} node
+   *         Node for which we are to get listeners.
+   */
+  getEventListeners: function (node) {
+    let parsers = this._eventParsers;
+    let dbg = this.parent().tabActor.makeDebugger();
+    let listeners = [];
+
+    for (let [, {getListeners, normalizeHandler}] of parsers) {
+      try {
+        let eventInfos = getListeners(node);
+
+        if (!eventInfos) {
+          continue;
+        }
+
+        for (let eventInfo of eventInfos) {
+          if (normalizeHandler) {
+            eventInfo.normalizeHandler = normalizeHandler;
+          }
+
+          this.processHandlerForEvent(node, listeners, dbg, eventInfo);
+        }
+      } catch (e) {
+        // An object attached to the node looked like a listener but wasn't...
+        // do nothing.
+      }
+    }
+
+    listeners.sort((a, b) => {
+      return a.type.localeCompare(b.type);
+    });
+
+    return listeners;
+  },
+
+  /**
+   * Process a handler
+   *
+   * @param  {Node} node
+   *         The node for which we want information.
+   * @param  {Array} events
+   *         The events array contains all event objects that we have gathered
+   *         so far.
+   * @param  {Debugger} dbg
+   *         JSDebugger instance.
+   * @param  {Object} eventInfo
+   *         See event-parsers.js.registerEventParser() for a description of the
+   *         eventInfo object.
+   *
+   * @return {Array}
+   *         An array of objects where a typical object looks like this:
+   *           {
+   *             type: "click",
+   *             handler: function() { doSomething() },
+   *             origin: "http://www.mozilla.com",
+   *             searchString: 'onclick="doSomething()"',
+   *             tags: tags,
+   *             DOM0: true,
+   *             capturing: true,
+   *             hide: {
+   *               dom0: true
+   *             }
+   *           }
+   */
+  processHandlerForEvent: function (node, listeners, dbg, eventInfo) {
+    let type = eventInfo.type || "";
+    let handler = eventInfo.handler;
+    let tags = eventInfo.tags || "";
+    let hide = eventInfo.hide || {};
+    let override = eventInfo.override || {};
+    let global = Cu.getGlobalForObject(handler);
+    let globalDO = dbg.addDebuggee(global);
+    let listenerDO = globalDO.makeDebuggeeValue(handler);
+
+    if (eventInfo.normalizeHandler) {
+      listenerDO = eventInfo.normalizeHandler(listenerDO);
+    }
+
+    // If the listener is an object with a 'handleEvent' method, use that.
+    if (listenerDO.class === "Object" || listenerDO.class === "XULElement") {
+      let desc;
+
+      while (!desc && listenerDO) {
+        desc = listenerDO.getOwnPropertyDescriptor("handleEvent");
+        listenerDO = listenerDO.proto;
+      }
+
+      if (desc && desc.value) {
+        listenerDO = desc.value;
+      }
+    }
+
+    if (listenerDO.isBoundFunction) {
+      listenerDO = listenerDO.boundTargetFunction;
+    }
+
+    let script = listenerDO.script;
+    let scriptSource = script.source.text;
+    let functionSource =
+      scriptSource.substr(script.sourceStart, script.sourceLength);
+
+    /*
+    The script returned is the whole script and
+    scriptSource.substr(script.sourceStart, script.sourceLength) returns
+    something like this:
+      () { doSomething(); }
+
+    So we need to use some regex magic to get the appropriate function info
+    e.g.:
+      () => { ... }
+      function doit() { ... }
+      doit: function() { ... }
+      es6func() { ... }
+      var|let|const foo = function () { ... }
+      function generator*() { ... }
+    */
+    let scriptBeforeFunc = scriptSource.substr(0, script.sourceStart);
+    let matches = scriptBeforeFunc.match(RX_FUNC_NAME);
+    if (matches && matches.length > 0) {
+      functionSource = matches[0].trim() + functionSource;
+    }
+
+    let dom0 = false;
+
+    if (typeof node.hasAttribute !== "undefined") {
+      dom0 = !!node.hasAttribute("on" + type);
+    } else {
+      dom0 = !!node["on" + type];
+    }
+
+    let line = script.startLine;
+    let url = script.url;
+    let origin = url + (dom0 ? "" : ":" + line);
+    let searchString;
+
+    if (dom0) {
+      searchString = "on" + type + "=\"" + script.source.text + "\"";
+    } else {
+      scriptSource = "    " + scriptSource;
+    }
+
+    let eventObj = {
+      type: typeof override.type !== "undefined" ? override.type : type,
+      handler: functionSource.trim(),
+      origin: typeof override.origin !== "undefined" ?
+                     override.origin : origin,
+      searchString: typeof override.searchString !== "undefined" ?
+                           override.searchString : searchString,
+      tags: tags,
+      DOM0: typeof override.dom0 !== "undefined" ? override.dom0 : dom0,
+      capturing: typeof override.capturing !== "undefined" ?
+                        override.capturing : eventInfo.capturing,
+      hide: hide
+    };
+
+    listeners.push(eventObj);
+
+    dbg.removeDebuggee(globalDO);
+  },
+
+  /**
+   * Returns a LongStringActor with the node's value.
+   */
+  getNodeValue: function () {
+    return new LongStringActor(this.conn, this.rawNode.nodeValue || "");
+  },
+
+  /**
+   * Set the node's value to a given string.
+   */
+  setNodeValue: function (value) {
+    this.rawNode.nodeValue = value;
+  },
+
+  /**
+   * Get a unique selector string for this node.
+   */
+  getUniqueSelector: function () {
+    if (Cu.isDeadWrapper(this.rawNode)) {
+      return "";
+    }
+    return CssLogic.findCssSelector(this.rawNode);
+  },
+
+  /**
+   * Scroll the selected node into view.
+   */
+  scrollIntoView: function () {
+    this.rawNode.scrollIntoView(true);
+  },
+
+  /**
+   * Get the node's image data if any (for canvas and img nodes).
+   * Returns an imageData object with the actual data being a LongStringActor
+   * and a size json object.
+   * The image data is transmitted as a base64 encoded png data-uri.
+   * The method rejects if the node isn't an image or if the image is missing
+   *
+   * Accepts a maxDim request parameter to resize images that are larger. This
+   * is important as the resizing occurs server-side so that image-data being
+   * transfered in the longstring back to the client will be that much smaller
+   */
+  getImageData: function (maxDim) {
+    return imageToImageData(this.rawNode, maxDim).then(imageData => {
+      return {
+        data: LongStringActor(this.conn, imageData.data),
+        size: imageData.size
+      };
+    });
+  },
+
+  /**
+   * Get all event listeners that are listening on this node.
+   */
+  getEventListenerInfo: function () {
+    if (this.rawNode.nodeName.toLowerCase() === "html") {
+      return this.getEventListeners(this.rawNode.ownerGlobal);
+    }
+    return this.getEventListeners(this.rawNode);
+  },
+
+  /**
+   * Modify a node's attributes.  Passed an array of modifications
+   * similar in format to "attributes" mutations.
+   * {
+   *   attributeName: <string>
+   *   attributeNamespace: <optional string>
+   *   newValue: <optional string> - If null or undefined, the attribute
+   *     will be removed.
+   * }
+   *
+   * Returns when the modifications have been made.  Mutations will
+   * be queued for any changes made.
+   */
+  modifyAttributes: function (modifications) {
+    let rawNode = this.rawNode;
+    for (let change of modifications) {
+      if (change.newValue == null) {
+        if (change.attributeNamespace) {
+          rawNode.removeAttributeNS(change.attributeNamespace,
+                                    change.attributeName);
+        } else {
+          rawNode.removeAttribute(change.attributeName);
+        }
+      } else if (change.attributeNamespace) {
+        rawNode.setAttributeNS(change.attributeNamespace, change.attributeName,
+                               change.newValue);
+      } else {
+        rawNode.setAttribute(change.attributeName, change.newValue);
+      }
+    }
+  },
+
+  /**
+   * Given the font and fill style, get the image data of a canvas with the
+   * preview text and font.
+   * Returns an imageData object with the actual data being a LongStringActor
+   * and the width of the text as a string.
+   * The image data is transmitted as a base64 encoded png data-uri.
+   */
+  getFontFamilyDataURL: function (font, fillStyle = "black") {
+    let doc = this.rawNode.ownerDocument;
+    let options = {
+      previewText: FONT_FAMILY_PREVIEW_TEXT,
+      previewFontSize: FONT_FAMILY_PREVIEW_TEXT_SIZE,
+      fillStyle: fillStyle
+    };
+    let { dataURL, size } = getFontPreviewData(font, doc, options);
+
+    return { data: LongStringActor(this.conn, dataURL), size: size };
+  }
+});
+
+/**
+ * Server side of a node list as returned by querySelectorAll()
+ */
+var NodeListActor = exports.NodeListActor = protocol.ActorClassWithSpec(nodeListSpec, {
+  typeName: "domnodelist",
+
+  initialize: function (walker, nodeList) {
+    protocol.Actor.prototype.initialize.call(this);
+    this.walker = walker;
+    this.nodeList = nodeList || [];
+  },
+
+  destroy: function () {
+    protocol.Actor.prototype.destroy.call(this);
+  },
+
+  /**
+   * Instead of storing a connection object, the NodeActor gets its connection
+   * from its associated walker.
+   */
+  get conn() {
+    return this.walker.conn;
+  },
+
+  /**
+   * Items returned by this actor should belong to the parent walker.
+   */
+  marshallPool: function () {
+    return this.walker;
+  },
+
+  // Returns the JSON representation of this object over the wire.
+  form: function () {
+    return {
+      actor: this.actorID,
+      length: this.nodeList ? this.nodeList.length : 0
+    };
+  },
+
+  /**
+   * Get a single node from the node list.
+   */
+  item: function (index) {
+    return this.walker.attachElement(this.nodeList[index]);
+  },
+
+  /**
+   * Get a range of the items from the node list.
+   */
+  items: function (start = 0, end = this.nodeList.length) {
+    let items = Array.prototype.slice.call(this.nodeList, start, end)
+      .map(item => this.walker._ref(item));
+    return this.walker.attachElements(items);
+  },
+
+  release: function () {}
+});
+
+/**
+ * Server side of the DOM walker.
+ */
+var WalkerActor = protocol.ActorClassWithSpec(walkerSpec, {
+  /**
+   * Create the WalkerActor
+   * @param DebuggerServerConnection conn
+   *    The server connection.
+   */
+  initialize: function (conn, tabActor, options) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.tabActor = tabActor;
+    this.rootWin = tabActor.window;
+    this.rootDoc = this.rootWin.document;
+    this._refMap = new Map();
+    this._pendingMutations = [];
+    this._activePseudoClassLocks = new Set();
+    this.showAllAnonymousContent = options.showAllAnonymousContent;
+
+    this.walkerSearch = new WalkerSearch(this);
+
+    // Nodes which have been removed from the client's known
+    // ownership tree are considered "orphaned", and stored in
+    // this set.
+    this._orphaned = new Set();
+
+    // The client can tell the walker that it is interested in a node
+    // even when it is orphaned with the `retainNode` method.  This
+    // list contains orphaned nodes that were so retained.
+    this._retainedOrphans = new Set();
+
+    this.onMutations = this.onMutations.bind(this);
+    this.onFrameLoad = this.onFrameLoad.bind(this);
+    this.onFrameUnload = this.onFrameUnload.bind(this);
+
+    events.on(tabActor, "will-navigate", this.onFrameUnload);
+    events.on(tabActor, "navigate", this.onFrameLoad);
+
+    // Ensure that the root document node actor is ready and
+    // managed.
+    this.rootNode = this.document();
+
+    this.layoutChangeObserver = getLayoutChangesObserver(this.tabActor);
+    this._onReflows = this._onReflows.bind(this);
+    this.layoutChangeObserver.on("reflows", this._onReflows);
+    this._onResize = this._onResize.bind(this);
+    this.layoutChangeObserver.on("resize", this._onResize);
+
+    this._onEventListenerChange = this._onEventListenerChange.bind(this);
+    eventListenerService.addListenerChangeListener(this._onEventListenerChange);
+  },
+
+  /**
+   * Callback for eventListenerService.addListenerChangeListener
+   * @param nsISimpleEnumerator changesEnum
+   *    enumerator of nsIEventListenerChange
+   */
+  _onEventListenerChange: function (changesEnum) {
+    let changes = changesEnum.enumerate();
+    while (changes.hasMoreElements()) {
+      let current = changes.getNext().QueryInterface(Ci.nsIEventListenerChange);
+      let target = current.target;
+
+      if (this._refMap.has(target)) {
+        let actor = this.getNode(target);
+        let mutation = {
+          type: "events",
+          target: actor.actorID,
+          hasEventListeners: actor._hasEventListeners
+        };
+        this.queueMutation(mutation);
+      }
+    }
+  },
+
+  // Returns the JSON representation of this object over the wire.
+  form: function () {
+    return {
+      actor: this.actorID,
+      root: this.rootNode.form(),
+      traits: {
+        // FF42+ Inspector starts managing the Walker, while the inspector also
+        // starts cleaning itself up automatically on client disconnection.
+        // So that there is no need to manually release the walker anymore.
+        autoReleased: true,
+        // XXX: It seems silly that we need to tell the front which capabilities
+        // its actor has in this way when the target can use actorHasMethod. If
+        // this was ported to the protocol (Bug 1157048) we could call that
+        // inside of custom front methods and not need to do traits for this.
+        multiFrameQuerySelectorAll: true,
+        textSearch: true,
+      }
+    };
+  },
+
+  toString: function () {
+    return "[WalkerActor " + this.actorID + "]";
+  },
+
+  getDocumentWalker: function (node, whatToShow) {
+    // Allow native anon content (like <video> controls) if preffed on
+    let nodeFilter = this.showAllAnonymousContent
+                        ? allAnonymousContentTreeWalkerFilter
+                        : standardTreeWalkerFilter;
+    return new DocumentWalker(node, this.rootWin, whatToShow, nodeFilter);
+  },
+
+  destroy: function () {
+    if (this._destroyed) {
+      return;
+    }
+    this._destroyed = true;
+    protocol.Actor.prototype.destroy.call(this);
+    try {
+      this.clearPseudoClassLocks();
+      this._activePseudoClassLocks = null;
+
+      this._hoveredNode = null;
+      this.rootWin = null;
+      this.rootDoc = null;
+      this.rootNode = null;
+      this.layoutHelpers = null;
+      this._orphaned = null;
+      this._retainedOrphans = null;
+      this._refMap = null;
+
+      events.off(this.tabActor, "will-navigate", this.onFrameUnload);
+      events.off(this.tabActor, "navigate", this.onFrameLoad);
+
+      this.onFrameLoad = null;
+      this.onFrameUnload = null;
+
+      this.walkerSearch.destroy();
+
+      this.layoutChangeObserver.off("reflows", this._onReflows);
+      this.layoutChangeObserver.off("resize", this._onResize);
+      this.layoutChangeObserver = null;
+      releaseLayoutChangesObserver(this.tabActor);
+
+      eventListenerService.removeListenerChangeListener(
+        this._onEventListenerChange);
+
+      this.onMutations = null;
+
+      this.layoutActor = null;
+      this.tabActor = null;
+
+      events.emit(this, "destroyed");
+    } catch (e) {
+      console.error(e);
+    }
+  },
+
+  release: function () {},
+
+  unmanage: function (actor) {
+    if (actor instanceof NodeActor) {
+      if (this._activePseudoClassLocks &&
+          this._activePseudoClassLocks.has(actor)) {
+        this.clearPseudoClassLocks(actor);
+      }
+      this._refMap.delete(actor.rawNode);
+    }
+    protocol.Actor.prototype.unmanage.call(this, actor);
+  },
+
+  /**
+   * Determine if the walker has come across this DOM node before.
+   * @param {DOMNode} rawNode
+   * @return {Boolean}
+   */
+  hasNode: function (rawNode) {
+    return this._refMap.has(rawNode);
+  },
+
+  /**
+   * If the walker has come across this DOM node before, then get the
+   * corresponding node actor.
+   * @param {DOMNode} rawNode
+   * @return {NodeActor}
+   */
+  getNode: function (rawNode) {
+    return this._refMap.get(rawNode);
+  },
+
+  _ref: function (node) {
+    let actor = this.getNode(node);
+    if (actor) {
+      return actor;
+    }
+
+    actor = new NodeActor(this, node);
+
+    // Add the node actor as a child of this walker actor, assigning
+    // it an actorID.
+    this.manage(actor);
+    this._refMap.set(node, actor);
+
+    if (node.nodeType === Ci.nsIDOMNode.DOCUMENT_NODE) {
+      actor.watchDocument(this.onMutations);
+    }
+    return actor;
+  },
+
+  _onReflows: function (reflows) {
+    // Going through the nodes the walker knows about, see which ones have
+    // had their display changed and send a display-change event if any
+    let changes = [];
+    for (let [node, actor] of this._refMap) {
+      if (Cu.isDeadWrapper(node)) {
+        continue;
+      }
+
+      let isDisplayed = actor.isDisplayed;
+      if (isDisplayed !== actor.wasDisplayed) {
+        changes.push(actor);
+        // Updating the original value
+        actor.wasDisplayed = isDisplayed;
+      }
+    }
+
+    if (changes.length) {
+      events.emit(this, "display-change", changes);
+    }
+  },
+
+  /**
+   * When the browser window gets resized, relay the event to the front.
+   */
+  _onResize: function () {
+    events.emit(this, "resize");
+  },
+
+  /**
+   * This is kept for backward-compatibility reasons with older remote targets.
+   * Targets prior to bug 916443.
+   *
+   * pick/cancelPick are used to pick a node on click on the content
+   * document. But in their implementation prior to bug 916443, they don't allow
+   * highlighting on hover.
+   * The client-side now uses the highlighter actor's pick and cancelPick
+   * methods instead. The client-side uses the the highlightable trait found in
+   * the root actor to determine which version of pick to use.
+   *
+   * As for highlight, the new highlighter actor is used instead of the walker's
+   * highlight method. Same here though, the client-side uses the highlightable
+   * trait to dertermine which to use.
+   *
+   * Keeping these actor methods for now allows newer client-side debuggers to
+   * inspect fxos 1.2 remote targets or older firefox desktop remote targets.
+   */
+  pick: function () {},
+  cancelPick: function () {},
+  highlight: function (node) {},
+
+  /**
+   * Ensures that the node is attached and it can be accessed from the root.
+   *
+   * @param {(Node|NodeActor)} nodes The nodes
+   * @return {Object} An object compatible with the disconnectedNode type.
+   */
+  attachElement: function (node) {
+    let { nodes, newParents } = this.attachElements([node]);
+    return {
+      node: nodes[0],
+      newParents: newParents
+    };
+  },
+
+  /**
+   * Ensures that the nodes are attached and they can be accessed from the root.
+   *
+   * @param {(Node[]|NodeActor[])} nodes The nodes
+   * @return {Object} An object compatible with the disconnectedNodeArray type.
+   */
+  attachElements: function (nodes) {
+    let nodeActors = [];
+    let newParents = new Set();
+    for (let node of nodes) {
+      if (!(node instanceof NodeActor)) {
+        // If an anonymous node was passed in and we aren't supposed to know
+        // about it, then consult with the document walker as the source of
+        // truth about which elements exist.
+        if (!this.showAllAnonymousContent && isAnonymous(node)) {
+          node = this.getDocumentWalker(node).currentNode;
+        }
+
+        node = this._ref(node);
+      }
+
+      this.ensurePathToRoot(node, newParents);
+      // If nodes may be an array of raw nodes, we're sure to only have
+      // NodeActors with the following array.
+      nodeActors.push(node);
+    }
+
+    return {
+      nodes: nodeActors,
+      newParents: [...newParents]
+    };
+  },
+
+  /**
+   * Return the document node that contains the given node,
+   * or the root node if no node is specified.
+   * @param NodeActor node
+   *        The node whose document is needed, or null to
+   *        return the root.
+   */
+  document: function (node) {
+    let doc = isNodeDead(node) ? this.rootDoc : nodeDocument(node.rawNode);
+    return this._ref(doc);
+  },
+
+  /**
+   * Return the documentElement for the document containing the
+   * given node.
+   * @param NodeActor node
+   *        The node whose documentElement is requested, or null
+   *        to use the root document.
+   */
+  documentElement: function (node) {
+    let elt = isNodeDead(node)
+              ? this.rootDoc.documentElement
+              : nodeDocument(node.rawNode).documentElement;
+    return this._ref(elt);
+  },
+
+  /**
+   * Return all parents of the given node, ordered from immediate parent
+   * to root.
+   * @param NodeActor node
+   *    The node whose parents are requested.
+   * @param object options
+   *    Named options, including:
+   *    `sameDocument`: If true, parents will be restricted to the same
+   *      document as the node.
+   *    `sameTypeRootTreeItem`: If true, this will not traverse across
+   *     different types of docshells.
+   */
+  parents: function (node, options = {}) {
+    if (isNodeDead(node)) {
+      return [];
+    }
+
+    let walker = this.getDocumentWalker(node.rawNode);
+    let parents = [];
+    let cur;
+    while ((cur = walker.parentNode())) {
+      if (options.sameDocument &&
+          nodeDocument(cur) != nodeDocument(node.rawNode)) {
+        break;
+      }
+
+      if (options.sameTypeRootTreeItem &&
+          nodeDocshell(cur).sameTypeRootTreeItem !=
+          nodeDocshell(node.rawNode).sameTypeRootTreeItem) {
+        break;
+      }
+
+      parents.push(this._ref(cur));
+    }
+    return parents;
+  },
+
+  parentNode: function (node) {
+    let walker = this.getDocumentWalker(node.rawNode);
+    let parent = walker.parentNode();
+    if (parent) {
+      return this._ref(parent);
+    }
+    return null;
+  },
+
+  /**
+   * If the given NodeActor only has a single text node as a child with a text
+   * content small enough to be inlined, return that child's NodeActor.
+   *
+   * @param NodeActor node
+   */
+  inlineTextChild: function (node) {
+    // Quick checks to prevent creating a new walker if possible.
+    if (node.isBeforePseudoElement ||
+        node.isAfterPseudoElement ||
+        node.rawNode.nodeType != Ci.nsIDOMNode.ELEMENT_NODE ||
+        node.rawNode.children.length > 0) {
+      return undefined;
+    }
+
+    let docWalker = this.getDocumentWalker(node.rawNode);
+    let firstChild = docWalker.firstChild();
+
+    // Bail out if:
+    // - more than one child
+    // - unique child is not a text node
+    // - unique child is a text node, but is too long to be inlined
+    if (!firstChild ||
+        docWalker.nextSibling() ||
+        firstChild.nodeType !== Ci.nsIDOMNode.TEXT_NODE ||
+        firstChild.nodeValue.length > gValueSummaryLength
+        ) {
+      return undefined;
+    }
+
+    return this._ref(firstChild);
+  },
+
+  /**
+   * Mark a node as 'retained'.
+   *
+   * A retained node is not released when `releaseNode` is called on its
+   * parent, or when a parent is released with the `cleanup` option to
+   * `getMutations`.
+   *
+   * When a retained node's parent is released, a retained mode is added to
+   * the walker's "retained orphans" list.
+   *
+   * Retained nodes can be deleted by providing the `force` option to
+   * `releaseNode`.  They will also be released when their document
+   * has been destroyed.
+   *
+   * Retaining a node makes no promise about its children;  They can
+   * still be removed by normal means.
+   */
+  retainNode: function (node) {
+    node.retained = true;
+  },
+
+  /**
+   * Remove the 'retained' mark from a node.  If the node was a
+   * retained orphan, release it.
+   */
+  unretainNode: function (node) {
+    node.retained = false;
+    if (this._retainedOrphans.has(node)) {
+      this._retainedOrphans.delete(node);
+      this.releaseNode(node);
+    }
+  },
+
+  /**
+   * Release actors for a node and all child nodes.
+   */
+  releaseNode: function (node, options = {}) {
+    if (isNodeDead(node)) {
+      return;
+    }
+
+    if (node.retained && !options.force) {
+      this._retainedOrphans.add(node);
+      return;
+    }
+
+    if (node.retained) {
+      // Forcing a retained node to go away.
+      this._retainedOrphans.delete(node);
+    }
+
+    let walker = this.getDocumentWalker(node.rawNode);
+
+    let child = walker.firstChild();
+    while (child) {
+      let childActor = this.getNode(child);
+      if (childActor) {
+        this.releaseNode(childActor, options);
+      }
+      child = walker.nextSibling();
+    }
+
+    node.destroy();
+  },
+
+  /**
+   * Add any nodes between `node` and the walker's root node that have not
+   * yet been seen by the client.
+   */
+  ensurePathToRoot: function (node, newParents = new Set()) {
+    if (!node) {
+      return newParents;
+    }
+    let walker = this.getDocumentWalker(node.rawNode);
+    let cur;
+    while ((cur = walker.parentNode())) {
+      let parent = this.getNode(cur);
+      if (!parent) {
+        // This parent didn't exist, so hasn't been seen by the client yet.
+        newParents.add(this._ref(cur));
+      } else {
+        // This parent did exist, so the client knows about it.
+        return newParents;
+      }
+    }
+    return newParents;
+  },
+
+  /**
+   * Return children of the given node.  By default this method will return
+   * all children of the node, but there are options that can restrict this
+   * to a more manageable subset.
+   *
+   * @param NodeActor node
+   *    The node whose children you're curious about.
+   * @param object options
+   *    Named options:
+   *    `maxNodes`: The set of nodes returned by the method will be no longer
+   *       than maxNodes.
+   *    `start`: If a node is specified, the list of nodes will start
+   *       with the given child.  Mutally exclusive with `center`.
+   *    `center`: If a node is specified, the given node will be as centered
+   *       as possible in the list, given how close to the ends of the child
+   *       list it is.  Mutually exclusive with `start`.
+   *    `whatToShow`: A bitmask of node types that should be included.  See
+   *       https://developer.mozilla.org/en-US/docs/Web/API/NodeFilter.
+   *
+   * @returns an object with three items:
+   *    hasFirst: true if the first child of the node is included in the list.
+   *    hasLast: true if the last child of the node is included in the list.
+   *    nodes: Child nodes returned by the request.
+   */
+  children: function (node, options = {}) {
+    if (isNodeDead(node)) {
+      return { hasFirst: true, hasLast: true, nodes: [] };
+    }
+
+    if (options.center && options.start) {
+      throw Error("Can't specify both 'center' and 'start' options.");
+    }
+    let maxNodes = options.maxNodes || -1;
+    if (maxNodes == -1) {
+      maxNodes = Number.MAX_VALUE;
+    }
+
+    // We're going to create a few document walkers with the same filter,
+    // make it easier.
+    let getFilteredWalker = documentWalkerNode => {
+      return this.getDocumentWalker(documentWalkerNode, options.whatToShow);
+    };
+
+    // Need to know the first and last child.
+    let rawNode = node.rawNode;
+    let firstChild = getFilteredWalker(rawNode).firstChild();
+    let lastChild = getFilteredWalker(rawNode).lastChild();
+
+    if (!firstChild) {
+      // No children, we're done.
+      return { hasFirst: true, hasLast: true, nodes: [] };
+    }
+
+    let start;
+    if (options.center) {
+      start = options.center.rawNode;
+    } else if (options.start) {
+      start = options.start.rawNode;
+    } else {
+      start = firstChild;
+    }
+
+    let nodes = [];
+
+    // Start by reading backward from the starting point if we're centering...
+    let backwardWalker = getFilteredWalker(start);
+    if (start != firstChild && options.center) {
+      backwardWalker.previousSibling();
+      let backwardCount = Math.floor(maxNodes / 2);
+      let backwardNodes = this._readBackward(backwardWalker, backwardCount);
+      nodes = backwardNodes;
+    }
+
+    // Then read forward by any slack left in the max children...
+    let forwardWalker = getFilteredWalker(start);
+    let forwardCount = maxNodes - nodes.length;
+    nodes = nodes.concat(this._readForward(forwardWalker, forwardCount));
+
+    // If there's any room left, it means we've run all the way to the end.
+    // If we're centering, check if there are more items to read at the front.
+    let remaining = maxNodes - nodes.length;
+    if (options.center && remaining > 0 && nodes[0].rawNode != firstChild) {
+      let firstNodes = this._readBackward(backwardWalker, remaining);
+
+      // Then put it all back together.
+      nodes = firstNodes.concat(nodes);
+    }
+
+    return {
+      hasFirst: nodes[0].rawNode == firstChild,
+      hasLast: nodes[nodes.length - 1].rawNode == lastChild,
+      nodes: nodes
+    };
+  },
+
+  /**
+   * Return siblings of the given node.  By default this method will return
+   * all siblings of the node, but there are options that can restrict this
+   * to a more manageable subset.
+   *
+   * If `start` or `center` are not specified, this method will center on the
+   * node whose siblings are requested.
+   *
+   * @param NodeActor node
+   *    The node whose children you're curious about.
+   * @param object options
+   *    Named options:
+   *    `maxNodes`: The set of nodes returned by the method will be no longer
+   *       than maxNodes.
+   *    `start`: If a node is specified, the list of nodes will start
+   *       with the given child.  Mutally exclusive with `center`.
+   *    `center`: If a node is specified, the given node will be as centered
+   *       as possible in the list, given how close to the ends of the child
+   *       list it is.  Mutually exclusive with `start`.
+   *    `whatToShow`: A bitmask of node types that should be included.  See
+   *       https://developer.mozilla.org/en-US/docs/Web/API/NodeFilter.
+   *
+   * @returns an object with three items:
+   *    hasFirst: true if the first child of the node is included in the list.
+   *    hasLast: true if the last child of the node is included in the list.
+   *    nodes: Child nodes returned by the request.
+   */
+  siblings: function (node, options = {}) {
+    if (isNodeDead(node)) {
+      return { hasFirst: true, hasLast: true, nodes: [] };
+    }
+
+    let parentNode = this.getDocumentWalker(node.rawNode, options.whatToShow)
+                         .parentNode();
+    if (!parentNode) {
+      return {
+        hasFirst: true,
+        hasLast: true,
+        nodes: [node]
+      };
+    }
+
+    if (!(options.start || options.center)) {
+      options.center = node;
+    }
+
+    return this.children(this._ref(parentNode), options);
+  },
+
+  /**
+   * Get the next sibling of a given node.  Getting nodes one at a time
+   * might be inefficient, be careful.
+   *
+   * @param object options
+   *    Named options:
+   *    `whatToShow`: A bitmask of node types that should be included.  See
+   *       https://developer.mozilla.org/en-US/docs/Web/API/NodeFilter.
+   */
+  nextSibling: function (node, options = {}) {
+    if (isNodeDead(node)) {
+      return null;
+    }
+
+    let walker = this.getDocumentWalker(node.rawNode, options.whatToShow);
+    let sibling = walker.nextSibling();
+    return sibling ? this._ref(sibling) : null;
+  },
+
+  /**
+   * Get the previous sibling of a given node.  Getting nodes one at a time
+   * might be inefficient, be careful.
+   *
+   * @param object options
+   *    Named options:
+   *    `whatToShow`: A bitmask of node types that should be included.  See
+   *       https://developer.mozilla.org/en-US/docs/Web/API/NodeFilter.
+   */
+  previousSibling: function (node, options = {}) {
+    if (isNodeDead(node)) {
+      return null;
+    }
+
+    let walker = this.getDocumentWalker(node.rawNode, options.whatToShow);
+    let sibling = walker.previousSibling();
+    return sibling ? this._ref(sibling) : null;
+  },
+
+  /**
+   * Helper function for the `children` method: Read forward in the sibling
+   * list into an array with `count` items, including the current node.
+   */
+  _readForward: function (walker, count) {
+    let ret = [];
+    let node = walker.currentNode;
+    do {
+      ret.push(this._ref(node));
+      node = walker.nextSibling();
+    } while (node && --count);
+    return ret;
+  },
+
+  /**
+   * Helper function for the `children` method: Read backward in the sibling
+   * list into an array with `count` items, including the current node.
+   */
+  _readBackward: function (walker, count) {
+    let ret = [];
+    let node = walker.currentNode;
+    do {
+      ret.push(this._ref(node));
+      node = walker.previousSibling();
+    } while (node && --count);
+    ret.reverse();
+    return ret;
+  },
+
+  /**
+   * Return the node that the parent process has asked to
+   * inspect. This node is expected to be stored in gInspectingNode
+   * (which is set by a message manager message to the child.js frame
+   * script). The node is returned over the remote debugging protocol
+   * as a NodeFront.
+   */
+  findInspectingNode: function () {
+    let node = gInspectingNode;
+    if (!node) {
+      return {};
+    }
+
+    return this.attachElement(node);
+  },
+
+  /**
+   * Return the first node in the document that matches the given selector.
+   * See https://developer.mozilla.org/en-US/docs/Web/API/Element.querySelector
+   *
+   * @param NodeActor baseNode
+   * @param string selector
+   */
+  querySelector: function (baseNode, selector) {
+    if (isNodeDead(baseNode)) {
+      return {};
+    }
+
+    let node = baseNode.rawNode.querySelector(selector);
+    if (!node) {
+      return {};
+    }
+
+    return this.attachElement(node);
+  },
+
+  /**
+   * Return a NodeListActor with all nodes that match the given selector.
+   * See https://developer.mozilla.org/en-US/docs/Web/API/Element.querySelectorAll
+   *
+   * @param NodeActor baseNode
+   * @param string selector
+   */
+  querySelectorAll: function (baseNode, selector) {
+    let nodeList = null;
+
+    try {
+      nodeList = baseNode.rawNode.querySelectorAll(selector);
+    } catch (e) {
+      // Bad selector. Do nothing as the selector can come from a searchbox.
+    }
+
+    return new NodeListActor(this, nodeList);
+  },
+
+  /**
+   * Get a list of nodes that match the given selector in all known frames of
+   * the current content page.
+   * @param {String} selector.
+   * @return {Array}
+   */
+  _multiFrameQuerySelectorAll: function (selector) {
+    let nodes = [];
+
+    for (let {document} of this.tabActor.windows) {
+      try {
+        nodes = [...nodes, ...document.querySelectorAll(selector)];
+      } catch (e) {
+        // Bad selector. Do nothing as the selector can come from a searchbox.
+      }
+    }
+
+    return nodes;
+  },
+
+  /**
+   * Return a NodeListActor with all nodes that match the given selector in all
+   * frames of the current content page.
+   * @param {String} selector
+   */
+  multiFrameQuerySelectorAll: function (selector) {
+    return new NodeListActor(this, this._multiFrameQuerySelectorAll(selector));
+  },
+
+  /**
+   * Search the document for a given string.
+   * Results will be searched with the walker-search module (searches through
+   * tag names, attribute names and values, and text contents).
+   *
+   * @returns {searchresult}
+   *            - {NodeList} list
+   *            - {Array<Object>} metadata. Extra information with indices that
+   *                              match up with node list.
+   */
+  search: function (query) {
+    let results = this.walkerSearch.search(query);
+    let nodeList = new NodeListActor(this, results.map(r => r.node));
+
+    return {
+      list: nodeList,
+      metadata: []
+    };
+  },
+
+  /**
+   * Returns a list of matching results for CSS selector autocompletion.
+   *
+   * @param string query
+   *        The selector query being completed
+   * @param string completing
+   *        The exact token being completed out of the query
+   * @param string selectorState
+   *        One of "pseudo", "id", "tag", "class", "null"
+   */
+  getSuggestionsForQuery: function (query, completing, selectorState) {
+    let sugs = {
+      classes: new Map(),
+      tags: new Map(),
+      ids: new Map()
+    };
+    let result = [];
+    let nodes = null;
+    // Filtering and sorting the results so that protocol transfer is miminal.
+    switch (selectorState) {
+      case "pseudo":
+        result = PSEUDO_SELECTORS.filter(item => {
+          return item[0].startsWith(":" + completing);
+        });
+        break;
+
+      case "class":
+        if (!query) {
+          nodes = this._multiFrameQuerySelectorAll("[class]");
+        } else {
+          nodes = this._multiFrameQuerySelectorAll(query);
+        }
+        for (let node of nodes) {
+          for (let className of node.classList) {
+            sugs.classes.set(className, (sugs.classes.get(className)|0) + 1);
+          }
+        }
+        sugs.classes.delete("");
+        sugs.classes.delete(HIDDEN_CLASS);
+        for (let [className, count] of sugs.classes) {
+          if (className.startsWith(completing)) {
+            result.push(["." + CSS.escape(className), count, selectorState]);
+          }
+        }
+        break;
+
+      case "id":
+        if (!query) {
+          nodes = this._multiFrameQuerySelectorAll("[id]");
+        } else {
+          nodes = this._multiFrameQuerySelectorAll(query);
+        }
+        for (let node of nodes) {
+          sugs.ids.set(node.id, (sugs.ids.get(node.id)|0) + 1);
+        }
+        for (let [id, count] of sugs.ids) {
+          if (id.startsWith(completing) && id !== "") {
+            result.push(["#" + CSS.escape(id), count, selectorState]);
+          }
+        }
+        break;
+
+      case "tag":
+        if (!query) {
+          nodes = this._multiFrameQuerySelectorAll("*");
+        } else {
+          nodes = this._multiFrameQuerySelectorAll(query);
+        }
+        for (let node of nodes) {
+          let tag = node.localName;
+          sugs.tags.set(tag, (sugs.tags.get(tag)|0) + 1);
+        }
+        for (let [tag, count] of sugs.tags) {
+          if ((new RegExp("^" + completing + ".*", "i")).test(tag)) {
+            result.push([tag, count, selectorState]);
+          }
+        }
+
+        // For state 'tag' (no preceding # or .) and when there's no query (i.e.
+        // only one word) then search for the matching classes and ids
+        if (!query) {
+          result = [
+            ...result,
+            ...this.getSuggestionsForQuery(null, completing, "class")
+                   .suggestions,
+            ...this.getSuggestionsForQuery(null, completing, "id")
+                   .suggestions
+          ];
+        }
+
+        break;
+
+      case "null":
+        nodes = this._multiFrameQuerySelectorAll(query);
+        for (let node of nodes) {
+          sugs.ids.set(node.id, (sugs.ids.get(node.id)|0) + 1);
+          let tag = node.localName;
+          sugs.tags.set(tag, (sugs.tags.get(tag)|0) + 1);
+          for (let className of node.classList) {
+            sugs.classes.set(className, (sugs.classes.get(className)|0) + 1);
+          }
+        }
+        for (let [tag, count] of sugs.tags) {
+          tag && result.push([tag, count]);
+        }
+        for (let [id, count] of sugs.ids) {
+          id && result.push(["#" + id, count]);
+        }
+        sugs.classes.delete("");
+        sugs.classes.delete(HIDDEN_CLASS);
+        for (let [className, count] of sugs.classes) {
+          className && result.push(["." + className, count]);
+        }
+    }
+
+    // Sort by count (desc) and name (asc)
+    result = result.sort((a, b) => {
+      // Computed a sortable string with first the inverted count, then the name
+      let sortA = (10000 - a[1]) + a[0];
+      let sortB = (10000 - b[1]) + b[0];
+
+      // Prefixing ids, classes and tags, to group results
+      let firstA = a[0].substring(0, 1);
+      let firstB = b[0].substring(0, 1);
+
+      if (firstA === "#") {
+        sortA = "2" + sortA;
+      } else if (firstA === ".") {
+        sortA = "1" + sortA;
+      } else {
+        sortA = "0" + sortA;
+      }
+
+      if (firstB === "#") {
+        sortB = "2" + sortB;
+      } else if (firstB === ".") {
+        sortB = "1" + sortB;
+      } else {
+        sortB = "0" + sortB;
+      }
+
+      // String compare
+      return sortA.localeCompare(sortB);
+    });
+
+    result.slice(0, 25);
+
+    return {
+      query: query,
+      suggestions: result
+    };
+  },
+
+  /**
+   * Add a pseudo-class lock to a node.
+   *
+   * @param NodeActor node
+   * @param string pseudo
+   *    A pseudoclass: ':hover', ':active', ':focus'
+   * @param options
+   *    Options object:
+   *    `parents`: True if the pseudo-class should be added
+   *      to parent nodes.
+   *
+   * @returns An empty packet.  A "pseudoClassLock" mutation will
+   *    be queued for any changed nodes.
+   */
+  addPseudoClassLock: function (node, pseudo, options = {}) {
+    if (isNodeDead(node)) {
+      return;
+    }
+
+    // There can be only one node locked per pseudo, so dismiss all existing
+    // ones
+    for (let locked of this._activePseudoClassLocks) {
+      if (DOMUtils.hasPseudoClassLock(locked.rawNode, pseudo)) {
+        this._removePseudoClassLock(locked, pseudo);
+      }
+    }
+
+    this._addPseudoClassLock(node, pseudo);
+
+    if (!options.parents) {
+      return;
+    }
+
+    let walker = this.getDocumentWalker(node.rawNode);
+    let cur;
+    while ((cur = walker.parentNode())) {
+      let curNode = this._ref(cur);
+      this._addPseudoClassLock(curNode, pseudo);
+    }
+  },
+
+  _queuePseudoClassMutation: function (node) {
+    this.queueMutation({
+      target: node.actorID,
+      type: "pseudoClassLock",
+      pseudoClassLocks: node.writePseudoClassLocks()
+    });
+  },
+
+  _addPseudoClassLock: function (node, pseudo) {
+    if (node.rawNode.nodeType !== Ci.nsIDOMNode.ELEMENT_NODE) {
+      return false;
+    }
+    DOMUtils.addPseudoClassLock(node.rawNode, pseudo);
+    this._activePseudoClassLocks.add(node);
+    this._queuePseudoClassMutation(node);
+    return true;
+  },
+
+  _installHelperSheet: function (node) {
+    if (!this.installedHelpers) {
+      this.installedHelpers = new WeakMap();
+    }
+    let win = node.rawNode.ownerDocument.defaultView;
+    if (!this.installedHelpers.has(win)) {
+      let { Style } = require("sdk/stylesheet/style");
+      let { attach } = require("sdk/content/mod");
+      let style = Style({source: HELPER_SHEET, type: "agent" });
+      attach(style, win);
+      this.installedHelpers.set(win, style);
+    }
+  },
+
+  hideNode: function (node) {
+    if (isNodeDead(node)) {
+      return;
+    }
+
+    this._installHelperSheet(node);
+    node.rawNode.classList.add(HIDDEN_CLASS);
+  },
+
+  unhideNode: function (node) {
+    if (isNodeDead(node)) {
+      return;
+    }
+
+    node.rawNode.classList.remove(HIDDEN_CLASS);
+  },
+
+  /**
+   * Remove a pseudo-class lock from a node.
+   *
+   * @param NodeActor node
+   * @param string pseudo
+   *    A pseudoclass: ':hover', ':active', ':focus'
+   * @param options
+   *    Options object:
+   *    `parents`: True if the pseudo-class should be removed
+   *      from parent nodes.
+   *
+   * @returns An empty response.  "pseudoClassLock" mutations
+   *    will be emitted for any changed nodes.
+   */
+  removePseudoClassLock: function (node, pseudo, options = {}) {
+    if (isNodeDead(node)) {
+      return;
+    }
+
+    this._removePseudoClassLock(node, pseudo);
+
+    // Remove pseudo class for children as we don't want to allow
+    // turning it on for some childs without setting it on some parents
+    for (let locked of this._activePseudoClassLocks) {
+      if (node.rawNode.contains(locked.rawNode) &&
+          DOMUtils.hasPseudoClassLock(locked.rawNode, pseudo)) {
+        this._removePseudoClassLock(locked, pseudo);
+      }
+    }
+
+    if (!options.parents) {
+      return;
+    }
+
+    let walker = this.getDocumentWalker(node.rawNode);
+    let cur;
+    while ((cur = walker.parentNode())) {
+      let curNode = this._ref(cur);
+      this._removePseudoClassLock(curNode, pseudo);
+    }
+  },
+
+  _removePseudoClassLock: function (node, pseudo) {
+    if (node.rawNode.nodeType != Ci.nsIDOMNode.ELEMENT_NODE) {
+      return false;
+    }
+    DOMUtils.removePseudoClassLock(node.rawNode, pseudo);
+    if (!node.writePseudoClassLocks()) {
+      this._activePseudoClassLocks.delete(node);
+    }
+
+    this._queuePseudoClassMutation(node);
+    return true;
+  },
+
+  /**
+   * Clear all the pseudo-classes on a given node or all nodes.
+   * @param {NodeActor} node Optional node to clear pseudo-classes on
+   */
+  clearPseudoClassLocks: function (node) {
+    if (node && isNodeDead(node)) {
+      return;
+    }
+
+    if (node) {
+      DOMUtils.clearPseudoClassLocks(node.rawNode);
+      this._activePseudoClassLocks.delete(node);
+      this._queuePseudoClassMutation(node);
+    } else {
+      for (let locked of this._activePseudoClassLocks) {
+        DOMUtils.clearPseudoClassLocks(locked.rawNode);
+        this._activePseudoClassLocks.delete(locked);
+        this._queuePseudoClassMutation(locked);
+      }
+    }
+  },
+
+  /**
+   * Get a node's innerHTML property.
+   */
+  innerHTML: function (node) {
+    let html = "";
+    if (!isNodeDead(node)) {
+      html = node.rawNode.innerHTML;
+    }
+    return LongStringActor(this.conn, html);
+  },
+
+  /**
+   * Set a node's innerHTML property.
+   *
+   * @param {NodeActor} node The node.
+   * @param {string} value The piece of HTML content.
+   */
+  setInnerHTML: function (node, value) {
+    if (isNodeDead(node)) {
+      return;
+    }
+
+    let rawNode = node.rawNode;
+    if (rawNode.nodeType !== rawNode.ownerDocument.ELEMENT_NODE) {
+      throw new Error("Can only change innerHTML to element nodes");
+    }
+    rawNode.innerHTML = value;
+  },
+
+  /**
+   * Get a node's outerHTML property.
+   *
+   * @param {NodeActor} node The node.
+   */
+  outerHTML: function (node) {
+    let outerHTML = "";
+    if (!isNodeDead(node)) {
+      outerHTML = node.rawNode.outerHTML;
+    }
+    return LongStringActor(this.conn, outerHTML);
+  },
+
+  /**
+   * Set a node's outerHTML property.
+   *
+   * @param {NodeActor} node The node.
+   * @param {string} value The piece of HTML content.
+   */
+  setOuterHTML: function (node, value) {
+    if (isNodeDead(node)) {
+      return;
+    }
+
+    let parsedDOM = DOMParser.parseFromString(value, "text/html");
+    let rawNode = node.rawNode;
+    let parentNode = rawNode.parentNode;
+
+    // Special case for head and body.  Setting document.body.outerHTML
+    // creates an extra <head> tag, and document.head.outerHTML creates
+    // an extra <body>.  So instead we will call replaceChild with the
+    // parsed DOM, assuming that they aren't trying to set both tags at once.
+    if (rawNode.tagName === "BODY") {
+      if (parsedDOM.head.innerHTML === "") {
+        parentNode.replaceChild(parsedDOM.body, rawNode);
+      } else {
+        rawNode.outerHTML = value;
+      }
+    } else if (rawNode.tagName === "HEAD") {
+      if (parsedDOM.body.innerHTML === "") {
+        parentNode.replaceChild(parsedDOM.head, rawNode);
+      } else {
+        rawNode.outerHTML = value;
+      }
+    } else if (node.isDocumentElement()) {
+      // Unable to set outerHTML on the document element.  Fall back by
+      // setting attributes manually, then replace the body and head elements.
+      let finalAttributeModifications = [];
+      let attributeModifications = {};
+      for (let attribute of rawNode.attributes) {
+        attributeModifications[attribute.name] = null;
+      }
+      for (let attribute of parsedDOM.documentElement.attributes) {
+        attributeModifications[attribute.name] = attribute.value;
+      }
+      for (let key in attributeModifications) {
+        finalAttributeModifications.push({
+          attributeName: key,
+          newValue: attributeModifications[key]
+        });
+      }
+      node.modifyAttributes(finalAttributeModifications);
+      rawNode.replaceChild(parsedDOM.head, rawNode.querySelector("head"));
+      rawNode.replaceChild(parsedDOM.body, rawNode.querySelector("body"));
+    } else {
+      rawNode.outerHTML = value;
+    }
+  },
+
+  /**
+   * Insert adjacent HTML to a node.
+   *
+   * @param {Node} node
+   * @param {string} position One of "beforeBegin", "afterBegin", "beforeEnd",
+   *                          "afterEnd" (see Element.insertAdjacentHTML).
+   * @param {string} value The HTML content.
+   */
+  insertAdjacentHTML: function (node, position, value) {
+    if (isNodeDead(node)) {
+      return {node: [], newParents: []};
+    }
+
+    let rawNode = node.rawNode;
+    let isInsertAsSibling = position === "beforeBegin" ||
+      position === "afterEnd";
+
+    // Don't insert anything adjacent to the document element.
+    if (isInsertAsSibling && node.isDocumentElement()) {
+      throw new Error("Can't insert adjacent element to the root.");
+    }
+
+    let rawParentNode = rawNode.parentNode;
+    if (!rawParentNode && isInsertAsSibling) {
+      throw new Error("Can't insert as sibling without parent node.");
+    }
+
+    // We can't use insertAdjacentHTML, because we want to return the nodes
+    // being created (so the front can remove them if the user undoes
+    // the change). So instead, use Range.createContextualFragment().
+    let range = rawNode.ownerDocument.createRange();
+    if (position === "beforeBegin" || position === "afterEnd") {
+      range.selectNode(rawNode);
+    } else {
+      range.selectNodeContents(rawNode);
+    }
+    let docFrag = range.createContextualFragment(value);
+    let newRawNodes = Array.from(docFrag.childNodes);
+    switch (position) {
+      case "beforeBegin":
+        rawParentNode.insertBefore(docFrag, rawNode);
+        break;
+      case "afterEnd":
+        // Note: if the second argument is null, rawParentNode.insertBefore
+        // behaves like rawParentNode.appendChild.
+        rawParentNode.insertBefore(docFrag, rawNode.nextSibling);
+        break;
+      case "afterBegin":
+        rawNode.insertBefore(docFrag, rawNode.firstChild);
+        break;
+      case "beforeEnd":
+        rawNode.appendChild(docFrag);
+        break;
+      default:
+        throw new Error("Invalid position value. Must be either " +
+          "'beforeBegin', 'beforeEnd', 'afterBegin' or 'afterEnd'.");
+    }
+
+    return this.attachElements(newRawNodes);
+  },
+
+  /**
+   * Duplicate a specified node
+   *
+   * @param {NodeActor} node The node to duplicate.
+   */
+  duplicateNode: function ({rawNode}) {
+    let clonedNode = rawNode.cloneNode(true);
+    rawNode.parentNode.insertBefore(clonedNode, rawNode.nextSibling);
+  },
+
+  /**
+   * Test whether a node is a document or a document element.
+   *
+   * @param {NodeActor} node The node to remove.
+   * @return {boolean} True if the node is a document or a document element.
+   */
+  isDocumentOrDocumentElementNode: function (node) {
+    return ((node.rawNode.ownerDocument &&
+      node.rawNode.ownerDocument.documentElement === this.rawNode) ||
+      node.rawNode.nodeType === Ci.nsIDOMNode.DOCUMENT_NODE);
+  },
+
+  /**
+   * Removes a node from its parent node.
+   *
+   * @param {NodeActor} node The node to remove.
+   * @returns The node's nextSibling before it was removed.
+   */
+  removeNode: function (node) {
+    if (isNodeDead(node) || this.isDocumentOrDocumentElementNode(node)) {
+      throw Error("Cannot remove document, document elements or dead nodes.");
+    }
+
+    let nextSibling = this.nextSibling(node);
+    node.rawNode.remove();
+    // Mutation events will take care of the rest.
+    return nextSibling;
+  },
+
+  /**
+   * Removes an array of nodes from their parent node.
+   *
+   * @param {NodeActor[]} nodes The nodes to remove.
+   */
+  removeNodes: function (nodes) {
+    // Check that all nodes are valid before processing the removals.
+    for (let node of nodes) {
+      if (isNodeDead(node) || this.isDocumentOrDocumentElementNode(node)) {
+        throw Error("Cannot remove document, document elements or dead nodes");
+      }
+    }
+
+    for (let node of nodes) {
+      node.rawNode.remove();
+      // Mutation events will take care of the rest.
+    }
+  },
+
+  /**
+   * Insert a node into the DOM.
+   */
+  insertBefore: function (node, parent, sibling) {
+    if (isNodeDead(node) ||
+        isNodeDead(parent) ||
+        (sibling && isNodeDead(sibling))) {
+      return;
+    }
+
+    let rawNode = node.rawNode;
+    let rawParent = parent.rawNode;
+    let rawSibling = sibling ? sibling.rawNode : null;
+
+    // Don't bother inserting a node if the document position isn't going
+    // to change. This prevents needless iframes reloading and mutations.
+    if (rawNode.parentNode === rawParent) {
+      let currentNextSibling = this.nextSibling(node);
+      currentNextSibling = currentNextSibling ? currentNextSibling.rawNode :
+                                                null;
+
+      if (rawNode === rawSibling || currentNextSibling === rawSibling) {
+        return;
+      }
+    }
+
+    rawParent.insertBefore(rawNode, rawSibling);
+  },
+
+  /**
+   * Editing a node's tagname actually means creating a new node with the same
+   * attributes, removing the node and inserting the new one instead.
+   * This method does not return anything as mutation events are taking care of
+   * informing the consumers about changes.
+   */
+  editTagName: function (node, tagName) {
+    if (isNodeDead(node)) {
+      return null;
+    }
+
+    let oldNode = node.rawNode;
+
+    // Create a new element with the same attributes as the current element and
+    // prepare to replace the current node with it.
+    let newNode;
+    try {
+      newNode = nodeDocument(oldNode).createElement(tagName);
+    } catch (x) {
+      // Failed to create a new element with that tag name, ignore the change,
+      // and signal the error to the front.
+      return Promise.reject(new Error("Could not change node's tagName to " + tagName));
+    }
+
+    let attrs = oldNode.attributes;
+    for (let i = 0; i < attrs.length; i++) {
+      newNode.setAttribute(attrs[i].name, attrs[i].value);
+    }
+
+    // Insert the new node, and transfer the old node's children.
+    oldNode.parentNode.insertBefore(newNode, oldNode);
+    while (oldNode.firstChild) {
+      newNode.appendChild(oldNode.firstChild);
+    }
+
+    oldNode.remove();
+    return null;
+  },
+
+  /**
+   * Get any pending mutation records.  Must be called by the client after
+   * the `new-mutations` notification is received.  Returns an array of
+   * mutation records.
+   *
+   * Mutation records have a basic structure:
+   *
+   * {
+   *   type: attributes|characterData|childList,
+   *   target: <domnode actor ID>,
+   * }
+   *
+   * And additional attributes based on the mutation type:
+   *
+   * `attributes` type:
+   *   attributeName: <string> - the attribute that changed
+   *   attributeNamespace: <string> - the attribute's namespace URI, if any.
+   *   newValue: <string> - The new value of the attribute, if any.
+   *
+   * `characterData` type:
+   *   newValue: <string> - the new nodeValue for the node
+   *
+   * `childList` type is returned when the set of children for a node
+   * has changed.  Includes extra data, which can be used by the client to
+   * maintain its ownership subtree.
+   *
+   *   added: array of <domnode actor ID> - The list of actors *previously
+   *     seen by the client* that were added to the target node.
+   *   removed: array of <domnode actor ID> The list of actors *previously
+   *     seen by the client* that were removed from the target node.
+   *   inlineTextChild: If the node now has a single text child, it will
+   *     be sent here.
+   *
+   * Actors that are included in a MutationRecord's `removed` but
+   * not in an `added` have been removed from the client's ownership
+   * tree (either by being moved under a node the client has seen yet
+   * or by being removed from the tree entirely), and is considered
+   * 'orphaned'.
+   *
+   * Keep in mind that if a node that the client hasn't seen is moved
+   * into or out of the target node, it will not be included in the
+   * removedNodes and addedNodes list, so if the client is interested
+   * in the new set of children it needs to issue a `children` request.
+   */
+  getMutations: function (options = {}) {
+    let pending = this._pendingMutations || [];
+    this._pendingMutations = [];
+
+    if (options.cleanup) {
+      for (let node of this._orphaned) {
+        // Release the orphaned node.  Nodes or children that have been
+        // retained will be moved to this._retainedOrphans.
+        this.releaseNode(node);
+      }
+      this._orphaned = new Set();
+    }
+
+    return pending;
+  },
+
+  queueMutation: function (mutation) {
+    if (!this.actorID || this._destroyed) {
+      // We've been destroyed, don't bother queueing this mutation.
+      return;
+    }
+    // We only send the `new-mutations` notification once, until the client
+    // fetches mutations with the `getMutations` packet.
+    let needEvent = this._pendingMutations.length === 0;
+
+    this._pendingMutations.push(mutation);
+
+    if (needEvent) {
+      events.emit(this, "new-mutations");
+    }
+  },
+
+  /**
+   * Handles mutations from the DOM mutation observer API.
+   *
+   * @param array[MutationRecord] mutations
+   *    See https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver#MutationRecord
+   */
+  onMutations: function (mutations) {
+    // Notify any observers that want *all* mutations (even on nodes that aren't
+    // referenced).  This is not sent over the protocol so can only be used by
+    // scripts running in the server process.
+    events.emit(this, "any-mutation");
+
+    for (let change of mutations) {
+      let targetActor = this.getNode(change.target);
+      if (!targetActor) {
+        continue;
+      }
+      let targetNode = change.target;
+      let type = change.type;
+      let mutation = {
+        type: type,
+        target: targetActor.actorID,
+      };
+
+      if (type === "attributes") {
+        mutation.attributeName = change.attributeName;
+        mutation.attributeNamespace = change.attributeNamespace || undefined;
+        mutation.newValue = targetNode.hasAttribute(mutation.attributeName) ?
+                            targetNode.getAttribute(mutation.attributeName)
+                            : null;
+      } else if (type === "characterData") {
+        mutation.newValue = targetNode.nodeValue;
+        this._maybeQueueInlineTextChildMutation(change, targetNode);
+      } else if (type === "childList" || type === "nativeAnonymousChildList") {
+        // Get the list of removed and added actors that the client has seen
+        // so that it can keep its ownership tree up to date.
+        let removedActors = [];
+        let addedActors = [];
+        for (let removed of change.removedNodes) {
+          let removedActor = this.getNode(removed);
+          if (!removedActor) {
+            // If the client never encountered this actor we don't need to
+            // mention that it was removed.
+            continue;
+          }
+          // While removed from the tree, nodes are saved as orphaned.
+          this._orphaned.add(removedActor);
+          removedActors.push(removedActor.actorID);
+        }
+        for (let added of change.addedNodes) {
+          let addedActor = this.getNode(added);
+          if (!addedActor) {
+            // If the client never encounted this actor we don't need to tell
+            // it about its addition for ownership tree purposes - if the
+            // client wants to see the new nodes it can ask for children.
+            continue;
+          }
+          // The actor is reconnected to the ownership tree, unorphan
+          // it and let the client know so that its ownership tree is up
+          // to date.
+          this._orphaned.delete(addedActor);
+          addedActors.push(addedActor.actorID);
+        }
+
+        mutation.numChildren = targetActor.numChildren;
+        mutation.removed = removedActors;
+        mutation.added = addedActors;
+
+        let inlineTextChild = this.inlineTextChild(targetActor);
+        if (inlineTextChild) {
+          mutation.inlineTextChild = inlineTextChild.form();
+        }
+      }
+      this.queueMutation(mutation);
+    }
+  },
+
+  /**
+   * Check if the provided mutation could change the way the target element is
+   * inlined with its parent node. If it might, a custom mutation of type
+   * "inlineTextChild" will be queued.
+   *
+   * @param {MutationRecord} mutation
+   *        A characterData type mutation
+   */
+  _maybeQueueInlineTextChildMutation: function (mutation) {
+    let {oldValue, target} = mutation;
+    let newValue = target.nodeValue;
+    let limit = gValueSummaryLength;
+
+    if ((oldValue.length <= limit && newValue.length <= limit) ||
+        (oldValue.length > limit && newValue.length > limit)) {
+      // Bail out if the new & old values are both below/above the size limit.
+      return;
+    }
+
+    let parentActor = this.getNode(target.parentNode);
+    if (!parentActor || parentActor.rawNode.children.length > 0) {
+      // If the parent node has other children, a character data mutation will
+      // not change anything regarding inlining text nodes.
+      return;
+    }
+
+    let inlineTextChild = this.inlineTextChild(parentActor);
+    this.queueMutation({
+      type: "inlineTextChild",
+      target: parentActor.actorID,
+      inlineTextChild:
+        inlineTextChild ? inlineTextChild.form() : undefined
+    });
+  },
+
+  onFrameLoad: function ({ window, isTopLevel }) {
+    if (isTopLevel) {
+      // If we initialize the inspector while the document is loading,
+      // we may already have a root document set in the constructor.
+      if (this.rootDoc && !Cu.isDeadWrapper(this.rootDoc) &&
+          this.rootDoc.defaultView) {
+        this.onFrameUnload({ window: this.rootDoc.defaultView });
+      }
+      this.rootDoc = window.document;
+      this.rootNode = this.document();
+      this.queueMutation({
+        type: "newRoot",
+        target: this.rootNode.form()
+      });
+      return;
+    }
+    let frame = getFrameElement(window);
+    let frameActor = this.getNode(frame);
+    if (!frameActor) {
+      return;
+    }
+
+    this.queueMutation({
+      type: "frameLoad",
+      target: frameActor.actorID,
+    });
+
+    // Send a childList mutation on the frame.
+    this.queueMutation({
+      type: "childList",
+      target: frameActor.actorID,
+      added: [],
+      removed: []
+    });
+  },
+
+  // Returns true if domNode is in window or a subframe.
+  _childOfWindow: function (window, domNode) {
+    let win = nodeDocument(domNode).defaultView;
+    while (win) {
+      if (win === window) {
+        return true;
+      }
+      win = getFrameElement(win);
+    }
+    return false;
+  },
+
+  onFrameUnload: function ({ window }) {
+    // Any retained orphans that belong to this document
+    // or its children need to be released, and a mutation sent
+    // to notify of that.
+    let releasedOrphans = [];
+
+    for (let retained of this._retainedOrphans) {
+      if (Cu.isDeadWrapper(retained.rawNode) ||
+          this._childOfWindow(window, retained.rawNode)) {
+        this._retainedOrphans.delete(retained);
+        releasedOrphans.push(retained.actorID);
+        this.releaseNode(retained, { force: true });
+      }
+    }
+
+    if (releasedOrphans.length > 0) {
+      this.queueMutation({
+        target: this.rootNode.actorID,
+        type: "unretained",
+        nodes: releasedOrphans
+      });
+    }
+
+    let doc = window.document;
+    let documentActor = this.getNode(doc);
+    if (!documentActor) {
+      return;
+    }
+
+    if (this.rootDoc === doc) {
+      this.rootDoc = null;
+      this.rootNode = null;
+    }
+
+    this.queueMutation({
+      type: "documentUnload",
+      target: documentActor.actorID
+    });
+
+    let walker = this.getDocumentWalker(doc);
+    let parentNode = walker.parentNode();
+    if (parentNode) {
+      // Send a childList mutation on the frame so that clients know
+      // they should reread the children list.
+      this.queueMutation({
+        type: "childList",
+        target: this.getNode(parentNode).actorID,
+        added: [],
+        removed: []
+      });
+    }
+
+    // Need to force a release of this node, because those nodes can't
+    // be accessed anymore.
+    this.releaseNode(documentActor, { force: true });
+  },
+
+  /**
+   * Check if a node is attached to the DOM tree of the current page.
+   * @param {nsIDomNode} rawNode
+   * @return {Boolean} false if the node is removed from the tree or within a
+   * document fragment
+   */
+  _isInDOMTree: function (rawNode) {
+    let walker = this.getDocumentWalker(rawNode);
+    let current = walker.currentNode;
+
+    // Reaching the top of tree
+    while (walker.parentNode()) {
+      current = walker.currentNode;
+    }
+
+    // The top of the tree is a fragment or is not rootDoc, hence rawNode isn't
+    // attached
+    if (current.nodeType === Ci.nsIDOMNode.DOCUMENT_FRAGMENT_NODE ||
+        current !== this.rootDoc) {
+      return false;
+    }
+
+    // Otherwise the top of the tree is rootDoc, hence rawNode is in rootDoc
+    return true;
+  },
+
+  /**
+   * @see _isInDomTree
+   */
+  isInDOMTree: function (node) {
+    if (isNodeDead(node)) {
+      return false;
+    }
+    return this._isInDOMTree(node.rawNode);
+  },
+
+  /**
+   * Given an ObjectActor (identified by its ID), commonly used in the debugger,
+   * webconsole and variablesView, return the corresponding inspector's
+   * NodeActor
+   */
+  getNodeActorFromObjectActor: function (objectActorID) {
+    let actor = this.conn.getActor(objectActorID);
+    if (!actor) {
+      return null;
+    }
+
+    let debuggerObject = this.conn.getActor(objectActorID).obj;
+    let rawNode = debuggerObject.unsafeDereference();
+
+    if (!this._isInDOMTree(rawNode)) {
+      return null;
+    }
+
+    // This is a special case for the document object whereby it is considered
+    // as document.documentElement (the <html> node)
+    if (rawNode.defaultView && rawNode === rawNode.defaultView.document) {
+      rawNode = rawNode.documentElement;
+    }
+
+    return this.attachElement(rawNode);
+  },
+
+  /**
+   * Given a StyleSheetActor (identified by its ID), commonly used in the
+   * style-editor, get its ownerNode and return the corresponding walker's
+   * NodeActor.
+   * Note that getNodeFromActor was added later and can now be used instead.
+   */
+  getStyleSheetOwnerNode: function (styleSheetActorID) {
+    return this.getNodeFromActor(styleSheetActorID, ["ownerNode"]);
+  },
+
+  /**
+   * This method can be used to retrieve NodeActor for DOM nodes from other
+   * actors in a way that they can later be highlighted in the page, or
+   * selected in the inspector.
+   * If an actor has a reference to a DOM node, and the UI needs to know about
+   * this DOM node (and possibly select it in the inspector), the UI should
+   * first retrieve a reference to the walkerFront:
+   *
+   * // Make sure the inspector/walker have been initialized first.
+   * toolbox.initInspector().then(() => {
+   *  // Retrieve the walker.
+   *  let walker = toolbox.walker;
+   * });
+   *
+   * And then call this method:
+   *
+   * // Get the nodeFront from my actor, passing the ID and properties path.
+   * walker.getNodeFromActor(myActorID, ["element"]).then(nodeFront => {
+   *   // Use the nodeFront, e.g. select the node in the inspector.
+   *   toolbox.getPanel("inspector").selection.setNodeFront(nodeFront);
+   * });
+   *
+   * @param {String} actorID The ID for the actor that has a reference to the
+   * DOM node.
+   * @param {Array} path Where, on the actor, is the DOM node stored. If in the
+   * scope of the actor, the node is available as `this.data.node`, then this
+   * should be ["data", "node"].
+   * @return {NodeActor} The attached NodeActor, or null if it couldn't be
+   * found.
+   */
+  getNodeFromActor: function (actorID, path) {
+    let actor = this.conn.getActor(actorID);
+    if (!actor) {
+      return null;
+    }
+
+    let obj = actor;
+    for (let name of path) {
+      if (!(name in obj)) {
+        return null;
+      }
+      obj = obj[name];
+    }
+
+    return this.attachElement(obj);
+  },
+
+  /**
+   * Returns an instance of the LayoutActor that is used to retrieve CSS layout-related
+   * information.
+   *
+   * @return {LayoutActor}
+   */
+  getLayoutInspector: function () {
+    if (!this.layoutActor) {
+      this.layoutActor = new LayoutActor(this.conn, this.tabActor, this);
+    }
+
+    return this.layoutActor;
+  },
+});
+
+/**
+ * Server side of the inspector actor, which is used to create
+ * inspector-related actors, including the walker.
+ */
+exports.InspectorActor = protocol.ActorClassWithSpec(inspectorSpec, {
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.tabActor = tabActor;
+
+    this._onColorPicked = this._onColorPicked.bind(this);
+    this._onColorPickCanceled = this._onColorPickCanceled.bind(this);
+    this.destroyEyeDropper = this.destroyEyeDropper.bind(this);
+  },
+
+  destroy: function () {
+    protocol.Actor.prototype.destroy.call(this);
+
+    this.destroyEyeDropper();
+
+    this._highlighterPromise = null;
+    this._pageStylePromise = null;
+    this._walkerPromise = null;
+    this.walker = null;
+    this.tabActor = null;
+  },
+
+  // Forces destruction of the actor and all its children
+  // like highlighter, walker and style actors.
+  disconnect: function () {
+    this.destroy();
+  },
+
+  get window() {
+    return this.tabActor.window;
+  },
+
+  getWalker: function (options = {}) {
+    if (this._walkerPromise) {
+      return this._walkerPromise;
+    }
+
+    let deferred = promise.defer();
+    this._walkerPromise = deferred.promise;
+
+    let window = this.window;
+    let domReady = () => {
+      let tabActor = this.tabActor;
+      window.removeEventListener("DOMContentLoaded", domReady, true);
+      this.walker = WalkerActor(this.conn, tabActor, options);
+      this.manage(this.walker);
+      events.once(this.walker, "destroyed", () => {
+        this._walkerPromise = null;
+        this._pageStylePromise = null;
+      });
+      deferred.resolve(this.walker);
+    };
+
+    if (window.document.readyState === "loading") {
+      window.addEventListener("DOMContentLoaded", domReady, true);
+    } else {
+      domReady();
+    }
+
+    return this._walkerPromise;
+  },
+
+  getPageStyle: function () {
+    if (this._pageStylePromise) {
+      return this._pageStylePromise;
+    }
+
+    this._pageStylePromise = this.getWalker().then(walker => {
+      let pageStyle = PageStyleActor(this);
+      this.manage(pageStyle);
+      return pageStyle;
+    });
+    return this._pageStylePromise;
+  },
+
+  /**
+   * The most used highlighter actor is the HighlighterActor which can be
+   * conveniently retrieved by this method.
+   * The same instance will always be returned by this method when called
+   * several times.
+   * The highlighter actor returned here is used to highlighter elements's
+   * box-models from the markup-view, box model, console, debugger, ... as
+   * well as select elements with the pointer (pick).
+   *
+   * @param {Boolean} autohide Optionally autohide the highlighter after an
+   * element has been picked
+   * @return {HighlighterActor}
+   */
+  getHighlighter: function (autohide) {
+    if (this._highlighterPromise) {
+      return this._highlighterPromise;
+    }
+
+    this._highlighterPromise = this.getWalker().then(walker => {
+      let highlighter = HighlighterActor(this, autohide);
+      this.manage(highlighter);
+      return highlighter;
+    });
+    return this._highlighterPromise;
+  },
+
+  /**
+   * If consumers need to display several highlighters at the same time or
+   * different types of highlighters, then this method should be used, passing
+   * the type name of the highlighter needed as argument.
+   * A new instance will be created everytime the method is called, so it's up
+   * to the consumer to release it when it is not needed anymore
+   *
+   * @param {String} type The type of highlighter to create
+   * @return {Highlighter} The highlighter actor instance or null if the
+   * typeName passed doesn't match any available highlighter
+   */
+  getHighlighterByType: function (typeName) {
+    if (isTypeRegistered(typeName)) {
+      return CustomHighlighterActor(this, typeName);
+    }
+    return null;
+  },
+
+  /**
+   * Get the node's image data if any (for canvas and img nodes).
+   * Returns an imageData object with the actual data being a LongStringActor
+   * and a size json object.
+   * The image data is transmitted as a base64 encoded png data-uri.
+   * The method rejects if the node isn't an image or if the image is missing
+   *
+   * Accepts a maxDim request parameter to resize images that are larger. This
+   * is important as the resizing occurs server-side so that image-data being
+   * transfered in the longstring back to the client will be that much smaller
+   */
+  getImageDataFromURL: function (url, maxDim) {
+    let img = new this.window.Image();
+    img.src = url;
+
+    // imageToImageData waits for the image to load.
+    return imageToImageData(img, maxDim).then(imageData => {
+      return {
+        data: LongStringActor(this.conn, imageData.data),
+        size: imageData.size
+      };
+    });
+  },
+
+  /**
+   * Resolve a URL to its absolute form, in the scope of a given content window.
+   * @param {String} url.
+   * @param {NodeActor} node If provided, the owner window of this node will be
+   * used to resolve the URL. Otherwise, the top-level content window will be
+   * used instead.
+   * @return {String} url.
+   */
+  resolveRelativeURL: function (url, node) {
+    let document = isNodeDead(node)
+                   ? this.window.document
+                   : nodeDocument(node.rawNode);
+
+    if (!document) {
+      return url;
+    }
+
+    let baseURI = Services.io.newURI(document.location.href, null, null);
+    return Services.io.newURI(url, null, baseURI).spec;
+  },
+
+  /**
+   * Create an instance of the eye-dropper highlighter and store it on this._eyeDropper.
+   * Note that for now, a new instance is created every time to deal with page navigation.
+   */
+  createEyeDropper: function () {
+    this.destroyEyeDropper();
+    this._highlighterEnv = new HighlighterEnvironment();
+    this._highlighterEnv.initFromTabActor(this.tabActor);
+    this._eyeDropper = new EyeDropper(this._highlighterEnv);
+  },
+
+  /**
+   * Destroy the current eye-dropper highlighter instance.
+   */
+  destroyEyeDropper: function () {
+    if (this._eyeDropper) {
+      this.cancelPickColorFromPage();
+      this._eyeDropper.destroy();
+      this._eyeDropper = null;
+      this._highlighterEnv.destroy();
+      this._highlighterEnv = null;
+    }
+  },
+
+  /**
+   * Pick a color from the page using the eye-dropper. This method doesn't return anything
+   * but will cause events to be sent to the front when a color is picked or when the user
+   * cancels the picker.
+   * @param {Object} options
+   */
+  pickColorFromPage: function (options) {
+    this.createEyeDropper();
+    this._eyeDropper.show(this.window.document.documentElement, options);
+    this._eyeDropper.once("selected", this._onColorPicked);
+    this._eyeDropper.once("canceled", this._onColorPickCanceled);
+    events.once(this.tabActor, "will-navigate", this.destroyEyeDropper);
+  },
+
+  /**
+   * After the pickColorFromPage method is called, the only way to dismiss the eye-dropper
+   * highlighter is for the user to click in the page and select a color. If you need to
+   * dismiss the eye-dropper programatically instead, use this method.
+   */
+  cancelPickColorFromPage: function () {
+    if (this._eyeDropper) {
+      this._eyeDropper.hide();
+      this._eyeDropper.off("selected", this._onColorPicked);
+      this._eyeDropper.off("canceled", this._onColorPickCanceled);
+      events.off(this.tabActor, "will-navigate", this.destroyEyeDropper);
+    }
+  },
+
+  _onColorPicked: function (e, color) {
+    events.emit(this, "color-picked", color);
+  },
+
+  _onColorPickCanceled: function () {
+    events.emit(this, "color-pick-canceled");
+  }
+});
+
+// Exported for test purposes.
+exports._documentWalker = DocumentWalker;
+
+function nodeDocument(node) {
+  if (Cu.isDeadWrapper(node)) {
+    return null;
+  }
+  return node.ownerDocument ||
+         (node.nodeType == Ci.nsIDOMNode.DOCUMENT_NODE ? node : null);
+}
+
+function nodeDocshell(node) {
+  let doc = node ? nodeDocument(node) : null;
+  let win = doc ? doc.defaultView : null;
+  if (win) {
+    return win.QueryInterface(Ci.nsIInterfaceRequestor)
+              .getInterface(Ci.nsIDocShell);
+  }
+  return null;
+}
+
+function isNodeDead(node) {
+  return !node || !node.rawNode || Cu.isDeadWrapper(node.rawNode);
+}
+
+/**
+ * Wrapper for inDeepTreeWalker.  Adds filtering to the traversal methods.
+ * See inDeepTreeWalker for more information about the methods.
+ *
+ * @param {DOMNode} node
+ * @param {Window} rootWin
+ * @param {Int} whatToShow See nodeFilterConstants / inIDeepTreeWalker for
+ * options.
+ * @param {Function} filter A custom filter function Taking in a DOMNode
+ *        and returning an Int. See WalkerActor.nodeFilter for an example.
+ */
+function DocumentWalker(node, rootWin,
+    whatToShow = nodeFilterConstants.SHOW_ALL,
+    filter = standardTreeWalkerFilter) {
+  if (!rootWin.location) {
+    throw new Error("Got an invalid root window in DocumentWalker");
+  }
+
+  this.walker = Cc["@mozilla.org/inspector/deep-tree-walker;1"]
+    .createInstance(Ci.inIDeepTreeWalker);
+  this.walker.showAnonymousContent = true;
+  this.walker.showSubDocuments = true;
+  this.walker.showDocumentsAsNodes = true;
+  this.walker.init(rootWin.document, whatToShow);
+  this.filter = filter;
+
+  // Make sure that the walker knows about the initial node (which could
+  // be skipped due to a filter).  Note that simply calling parentNode()
+  // causes currentNode to be updated.
+  this.walker.currentNode = node;
+  while (node &&
+         this.filter(node) === nodeFilterConstants.FILTER_SKIP) {
+    node = this.walker.parentNode();
+  }
+}
+
+DocumentWalker.prototype = {
+  get node() {
+    return this.walker.node;
+  },
+  get whatToShow() {
+    return this.walker.whatToShow;
+  },
+  get currentNode() {
+    return this.walker.currentNode;
+  },
+  set currentNode(val) {
+    this.walker.currentNode = val;
+  },
+
+  parentNode: function () {
+    return this.walker.parentNode();
+  },
+
+  nextNode: function () {
+    let node = this.walker.currentNode;
+    if (!node) {
+      return null;
+    }
+
+    let nextNode = this.walker.nextNode();
+    while (nextNode &&
+           this.filter(nextNode) === nodeFilterConstants.FILTER_SKIP) {
+      nextNode = this.walker.nextNode();
+    }
+
+    return nextNode;
+  },
+
+  firstChild: function () {
+    let node = this.walker.currentNode;
+    if (!node) {
+      return null;
+    }
+
+    let firstChild = this.walker.firstChild();
+    while (firstChild &&
+           this.filter(firstChild) === nodeFilterConstants.FILTER_SKIP) {
+      firstChild = this.walker.nextSibling();
+    }
+
+    return firstChild;
+  },
+
+  lastChild: function () {
+    let node = this.walker.currentNode;
+    if (!node) {
+      return null;
+    }
+
+    let lastChild = this.walker.lastChild();
+    while (lastChild &&
+           this.filter(lastChild) === nodeFilterConstants.FILTER_SKIP) {
+      lastChild = this.walker.previousSibling();
+    }
+
+    return lastChild;
+  },
+
+  previousSibling: function () {
+    let node = this.walker.previousSibling();
+    while (node && this.filter(node) === nodeFilterConstants.FILTER_SKIP) {
+      node = this.walker.previousSibling();
+    }
+    return node;
+  },
+
+  nextSibling: function () {
+    let node = this.walker.nextSibling();
+    while (node && this.filter(node) === nodeFilterConstants.FILTER_SKIP) {
+      node = this.walker.nextSibling();
+    }
+    return node;
+  }
+};
+
+function isInXULDocument(el) {
+  let doc = nodeDocument(el);
+  return doc &&
+         doc.documentElement &&
+         doc.documentElement.namespaceURI === XUL_NS;
+}
+
+/**
+ * This DeepTreeWalker filter skips whitespace text nodes and anonymous
+ * content with the exception of ::before and ::after and anonymous content
+ * in XUL document (needed to show all elements in the browser toolbox).
+ */
+function standardTreeWalkerFilter(node) {
+  // ::before and ::after are native anonymous content, but we always
+  // want to show them
+  if (node.nodeName === "_moz_generated_content_before" ||
+      node.nodeName === "_moz_generated_content_after") {
+    return nodeFilterConstants.FILTER_ACCEPT;
+  }
+
+  // Ignore empty whitespace text nodes that do not impact the layout.
+  if (isWhitespaceTextNode(node)) {
+    return nodeHasSize(node)
+           ? nodeFilterConstants.FILTER_ACCEPT
+           : nodeFilterConstants.FILTER_SKIP;
+  }
+
+  // Ignore all native and XBL anonymous content inside a non-XUL document
+  if (!isInXULDocument(node) && (isXBLAnonymous(node) ||
+                                  isNativeAnonymous(node))) {
+    // Note: this will skip inspecting the contents of feedSubscribeLine since
+    // that's XUL content injected in an HTML document, but we need to because
+    // this also skips many other elements that need to be skipped - like form
+    // controls, scrollbars, video controls, etc (see bug 1187482).
+    return nodeFilterConstants.FILTER_SKIP;
+  }
+
+  return nodeFilterConstants.FILTER_ACCEPT;
+}
+
+/**
+ * This DeepTreeWalker filter is like standardTreeWalkerFilter except that
+ * it also includes all anonymous content (like internal form controls).
+ */
+function allAnonymousContentTreeWalkerFilter(node) {
+  // Ignore empty whitespace text nodes that do not impact the layout.
+  if (isWhitespaceTextNode(node)) {
+    return nodeHasSize(node)
+           ? nodeFilterConstants.FILTER_ACCEPT
+           : nodeFilterConstants.FILTER_SKIP;
+  }
+  return nodeFilterConstants.FILTER_ACCEPT;
+}
+
+/**
+ * Is the given node a text node composed of whitespace only?
+ * @param {DOMNode} node
+ * @return {Boolean}
+ */
+function isWhitespaceTextNode(node) {
+  return node.nodeType == Ci.nsIDOMNode.TEXT_NODE && !/[^\s]/.exec(node.nodeValue);
+}
+
+/**
+ * Does the given node have non-0 width and height?
+ * @param {DOMNode} node
+ * @return {Boolean}
+ */
+function nodeHasSize(node) {
+  if (!node.getBoxQuads) {
+    return false;
+  }
+
+  let quads = node.getBoxQuads();
+  return quads.length && quads.some(quad => quad.bounds.width && quad.bounds.height);
+}
+
+/**
+ * Returns a promise that is settled once the given HTMLImageElement has
+ * finished loading.
+ *
+ * @param {HTMLImageElement} image - The image element.
+ * @param {Number} timeout - Maximum amount of time the image is allowed to load
+ * before the waiting is aborted. Ignored if flags.testing is set.
+ *
+ * @return {Promise} that is fulfilled once the image has loaded. If the image
+ * fails to load or the load takes too long, the promise is rejected.
+ */
+function ensureImageLoaded(image, timeout) {
+  let { HTMLImageElement } = image.ownerDocument.defaultView;
+  if (!(image instanceof HTMLImageElement)) {
+    return promise.reject("image must be an HTMLImageELement");
+  }
+
+  if (image.complete) {
+    // The image has already finished loading.
+    return promise.resolve();
+  }
+
+  // This image is still loading.
+  let onLoad = AsyncUtils.listenOnce(image, "load");
+
+  // Reject if loading fails.
+  let onError = AsyncUtils.listenOnce(image, "error").then(() => {
+    return promise.reject("Image '" + image.src + "' failed to load.");
+  });
+
+  // Don't timeout when testing. This is never settled.
+  let onAbort = new Promise(() => {});
+
+  if (!flags.testing) {
+    // Tests are not running. Reject the promise after given timeout.
+    onAbort = DevToolsUtils.waitForTime(timeout).then(() => {
+      return promise.reject("Image '" + image.src + "' took too long to load.");
+    });
+  }
+
+  // See which happens first.
+  return promise.race([onLoad, onError, onAbort]);
+}
+
+/**
+ * Given an <img> or <canvas> element, return the image data-uri. If @param node
+ * is an <img> element, the method waits a while for the image to load before
+ * the data is generated. If the image does not finish loading in a reasonable
+ * time (IMAGE_FETCHING_TIMEOUT milliseconds) the process aborts.
+ *
+ * @param {HTMLImageElement|HTMLCanvasElement} node - The <img> or <canvas>
+ * element, or Image() object. Other types cause the method to reject.
+ * @param {Number} maxDim - Optionally pass a maximum size you want the longest
+ * side of the image to be resized to before getting the image data.
+
+ * @return {Promise} A promise that is fulfilled with an object containing the
+ * data-uri and size-related information:
+ * { data: "...",
+ *   size: {
+ *     naturalWidth: 400,
+ *     naturalHeight: 300,
+ *     resized: true }
+ *  }.
+ *
+ * If something goes wrong, the promise is rejected.
+ */
+var imageToImageData = Task.async(function* (node, maxDim) {
+  let { HTMLCanvasElement, HTMLImageElement } = node.ownerDocument.defaultView;
+
+  let isImg = node instanceof HTMLImageElement;
+  let isCanvas = node instanceof HTMLCanvasElement;
+
+  if (!isImg && !isCanvas) {
+    throw new Error("node is not a <canvas> or <img> element.");
+  }
+
+  if (isImg) {
+    // Ensure that the image is ready.
+    yield ensureImageLoaded(node, IMAGE_FETCHING_TIMEOUT);
+  }
+
+  // Get the image resize ratio if a maxDim was provided
+  let resizeRatio = 1;
+  let imgWidth = node.naturalWidth || node.width;
+  let imgHeight = node.naturalHeight || node.height;
+  let imgMax = Math.max(imgWidth, imgHeight);
+  if (maxDim && imgMax > maxDim) {
+    resizeRatio = maxDim / imgMax;
+  }
+
+  // Extract the image data
+  let imageData;
+  // The image may already be a data-uri, in which case, save ourselves the
+  // trouble of converting via the canvas.drawImage.toDataURL method, but only
+  // if the image doesn't need resizing
+  if (isImg && node.src.startsWith("data:") && resizeRatio === 1) {
+    imageData = node.src;
+  } else {
+    // Create a canvas to copy the rawNode into and get the imageData from
+    let canvas = node.ownerDocument.createElementNS(XHTML_NS, "canvas");
+    canvas.width = imgWidth * resizeRatio;
+    canvas.height = imgHeight * resizeRatio;
+    let ctx = canvas.getContext("2d");
+
+    // Copy the rawNode image or canvas in the new canvas and extract data
+    ctx.drawImage(node, 0, 0, canvas.width, canvas.height);
+    imageData = canvas.toDataURL("image/png");
+  }
+
+  return {
+    data: imageData,
+    size: {
+      naturalWidth: imgWidth,
+      naturalHeight: imgHeight,
+      resized: resizeRatio !== 1
+    }
+  };
+});
+
+loader.lazyGetter(this, "DOMUtils", function () {
+  return Cc["@mozilla.org/inspector/dom-utils;1"].getService(Ci.inIDOMUtils);
+});
diff --git a/devtools/server/actors/layout.js b/devtools/server/actors/layout.js
new file mode 100644
index 000000000..0b9242b5f
--- /dev/null
+++ b/devtools/server/actors/layout.js
@@ -0,0 +1,131 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Actor, ActorClassWithSpec } = require("devtools/shared/protocol");
+const { gridSpec, layoutSpec } = require("devtools/shared/specs/layout");
+const { getStringifiableFragments } = require("devtools/server/actors/utils/css-grid-utils");
+
+/**
+ * Set of actors the expose the CSS layout information to the devtools protocol clients.
+ *
+ * The |Layout| actor is the main entry point. It is used to get various CSS
+ * layout-related information from the document.
+ *
+ * The |Grid| actor provides the grid fragment information to inspect the grid container.
+ */
+
+/**
+ * The GridActor provides information about a given grid's fragment data.
+ */
+var GridActor = ActorClassWithSpec(gridSpec, {
+  /**
+   * @param  {LayoutActor} layoutActor
+   *         The LayoutActor instance.
+   * @param  {DOMNode} containerEl
+   *         The grid container element.
+   */
+  initialize: function (layoutActor, containerEl) {
+    Actor.prototype.initialize.call(this, layoutActor.conn);
+
+    this.containerEl = containerEl;
+    this.walker = layoutActor.walker;
+  },
+
+  destroy: function () {
+    Actor.prototype.destroy.call(this);
+
+    this.containerEl = null;
+    this.gridFragments = null;
+    this.walker = null;
+  },
+
+  form: function (detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    // Seralize the grid fragment data into JSON so protocol.js knows how to write
+    // and read the data.
+    let gridFragments = this.containerEl.getGridFragments();
+    this.gridFragments = getStringifiableFragments(gridFragments);
+
+    let form = {
+      actor: this.actorID,
+      gridFragments: this.gridFragments
+    };
+
+    return form;
+  },
+});
+
+/**
+ * The CSS layout actor provides layout information for the given document.
+ */
+var LayoutActor = ActorClassWithSpec(layoutSpec, {
+  initialize: function (conn, tabActor, walker) {
+    Actor.prototype.initialize.call(this, conn);
+
+    this.tabActor = tabActor;
+    this.walker = walker;
+  },
+
+  destroy: function () {
+    Actor.prototype.destroy.call(this);
+
+    this.tabActor = null;
+    this.walker = null;
+  },
+
+  /**
+   * Returns an array of GridActor objects for all the grid containers found by iterating
+   * below the given rootNode.
+   *
+   * @param  {Node|NodeActor} rootNode
+   *         The root node to start iterating at.
+   * @return {Array} An array of GridActor objects.
+   */
+  getGrids: function (rootNode) {
+    let grids = [];
+
+    let treeWalker = this.walker.getDocumentWalker(rootNode);
+    while (treeWalker.nextNode()) {
+      let currentNode = treeWalker.currentNode;
+
+      if (currentNode.getGridFragments && currentNode.getGridFragments().length > 0) {
+        let gridActor = new GridActor(this, currentNode);
+        grids.push(gridActor);
+      }
+    }
+
+    return grids;
+  },
+
+  /**
+   * Returns an array of GridActor objects for all existing grid containers found by
+   * iterating below the given rootNode and optionally including nested frames.
+   *
+   * @param  {NodeActor} rootNode
+   * @param  {Boolean} traverseFrames
+   *         Whether or not we should iterate through nested frames.
+   * @return {Array} An array of GridActor objects.
+   */
+  getAllGrids: function (rootNode, traverseFrames) {
+    if (!traverseFrames) {
+      return this.getGridActors(rootNode);
+    }
+
+    let grids = [];
+    for (let {document} of this.tabActor.windows) {
+      grids = [...grids, ...this.getGrids(document.documentElement)];
+    }
+
+    return grids;
+  },
+
+});
+
+exports.GridActor = GridActor;
+exports.LayoutActor = LayoutActor;
diff --git a/devtools/server/actors/memory.js b/devtools/server/actors/memory.js
new file mode 100644
index 000000000..5c41a7dc1
--- /dev/null
+++ b/devtools/server/actors/memory.js
@@ -0,0 +1,83 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const protocol = require("devtools/shared/protocol");
+const { Memory } = require("devtools/server/performance/memory");
+const { actorBridgeWithSpec } = require("devtools/server/actors/common");
+const { memorySpec } = require("devtools/shared/specs/memory");
+loader.lazyRequireGetter(this, "events", "sdk/event/core");
+loader.lazyRequireGetter(this, "StackFrameCache",
+                         "devtools/server/actors/utils/stack", true);
+
+/**
+ * An actor that returns memory usage data for its parent actor's window.
+ * A tab-scoped instance of this actor will measure the memory footprint of its
+ * parent tab. A global-scoped instance however, will measure the memory
+ * footprint of the chrome window referenced by the root actor.
+ *
+ * This actor wraps the Memory module at devtools/server/performance/memory.js
+ * and provides RDP definitions.
+ *
+ * @see devtools/server/performance/memory.js for documentation.
+ */
+exports.MemoryActor = protocol.ActorClassWithSpec(memorySpec, {
+  initialize: function (conn, parent, frameCache = new StackFrameCache()) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+
+    this._onGarbageCollection = this._onGarbageCollection.bind(this);
+    this._onAllocations = this._onAllocations.bind(this);
+    this.bridge = new Memory(parent, frameCache);
+    this.bridge.on("garbage-collection", this._onGarbageCollection);
+    this.bridge.on("allocations", this._onAllocations);
+  },
+
+  destroy: function () {
+    this.bridge.off("garbage-collection", this._onGarbageCollection);
+    this.bridge.off("allocations", this._onAllocations);
+    this.bridge.destroy();
+    protocol.Actor.prototype.destroy.call(this);
+  },
+
+  attach: actorBridgeWithSpec("attach"),
+
+  detach: actorBridgeWithSpec("detach"),
+
+  getState: actorBridgeWithSpec("getState"),
+
+  saveHeapSnapshot: function (boundaries) {
+    return this.bridge.saveHeapSnapshot(boundaries);
+  },
+
+  takeCensus: actorBridgeWithSpec("takeCensus"),
+
+  startRecordingAllocations: actorBridgeWithSpec("startRecordingAllocations"),
+
+  stopRecordingAllocations: actorBridgeWithSpec("stopRecordingAllocations"),
+
+  getAllocationsSettings: actorBridgeWithSpec("getAllocationsSettings"),
+
+  getAllocations: actorBridgeWithSpec("getAllocations"),
+
+  forceGarbageCollection: actorBridgeWithSpec("forceGarbageCollection"),
+
+  forceCycleCollection: actorBridgeWithSpec("forceCycleCollection"),
+
+  measure: actorBridgeWithSpec("measure"),
+
+  residentUnique: actorBridgeWithSpec("residentUnique"),
+
+  _onGarbageCollection: function (data) {
+    if (this.conn.transport) {
+      events.emit(this, "garbage-collection", data);
+    }
+  },
+
+  _onAllocations: function (data) {
+    if (this.conn.transport) {
+      events.emit(this, "allocations", data);
+    }
+  },
+});
diff --git a/devtools/server/actors/monitor.js b/devtools/server/actors/monitor.js
new file mode 100644
index 000000000..17b076a9e
--- /dev/null
+++ b/devtools/server/actors/monitor.js
@@ -0,0 +1,145 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {Ci, Cc} = require("chrome");
+const {XPCOMUtils} = require("resource://gre/modules/XPCOMUtils.jsm");
+const Services = require("Services");
+
+function MonitorActor(aConnection) {
+  this.conn = aConnection;
+  this._updates = [];
+  this._started = false;
+}
+
+MonitorActor.prototype = {
+  actorPrefix: "monitor",
+
+  // Updates.
+
+  _sendUpdate: function () {
+    if (this._started) {
+      this.conn.sendActorEvent(this.actorID, "update", { data: this._updates });
+      this._updates = [];
+    }
+  },
+
+  // Methods available from the front.
+
+  start: function () {
+    if (!this._started) {
+      this._started = true;
+      Services.obs.addObserver(this, "devtools-monitor-update", false);
+      Services.obs.notifyObservers(null, "devtools-monitor-start", "");
+      this._agents.forEach(agent => this._startAgent(agent));
+    }
+    return {};
+  },
+
+  stop: function () {
+    if (this._started) {
+      this._agents.forEach(agent => agent.stop());
+      Services.obs.notifyObservers(null, "devtools-monitor-stop", "");
+      Services.obs.removeObserver(this, "devtools-monitor-update");
+      this._started = false;
+    }
+    return {};
+  },
+
+  disconnect: function () {
+    this.stop();
+  },
+
+  // nsIObserver.
+
+  observe: function (subject, topic, data) {
+    if (topic == "devtools-monitor-update") {
+      try {
+        data = JSON.parse(data);
+      } catch (e) {
+        console.error("Observer notification data is not a valid JSON-string:",
+                      data, e.message);
+        return;
+      }
+      if (!Array.isArray(data)) {
+        this._updates.push(data);
+      } else {
+        this._updates = this._updates.concat(data);
+      }
+      this._sendUpdate();
+    }
+  },
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver]),
+
+  // Update agents (see USSAgent for an example).
+
+  _agents: [],
+
+  _startAgent: function (agent) {
+    try {
+      agent.start();
+    } catch (e) {
+      this._removeAgent(agent);
+    }
+  },
+
+  _addAgent: function (agent) {
+    this._agents.push(agent);
+    if (this._started) {
+      this._startAgent(agent);
+    }
+  },
+
+  _removeAgent: function (agent) {
+    let index = this._agents.indexOf(agent);
+    if (index > -1) {
+      this._agents.splice(index, 1);
+    }
+  },
+};
+
+MonitorActor.prototype.requestTypes = {
+  "start": MonitorActor.prototype.start,
+  "stop": MonitorActor.prototype.stop,
+};
+
+exports.MonitorActor = MonitorActor;
+
+var USSAgent = {
+  _mgr: null,
+  _timeout: null,
+  _packet: {
+    graph: "USS",
+    time: null,
+    value: null
+  },
+
+  start: function () {
+    USSAgent._mgr = Cc["@mozilla.org/memory-reporter-manager;1"].getService(Ci.nsIMemoryReporterManager);
+    if (!USSAgent._mgr.residentUnique) {
+      throw "Couldn't get USS.";
+    }
+    USSAgent.update();
+  },
+
+  update: function () {
+    if (!USSAgent._mgr) {
+      USSAgent.stop();
+      return;
+    }
+    USSAgent._packet.time = Date.now();
+    USSAgent._packet.value = USSAgent._mgr.residentUnique;
+    Services.obs.notifyObservers(null, "devtools-monitor-update", JSON.stringify(USSAgent._packet));
+    USSAgent._timeout = setTimeout(USSAgent.update, 300);
+  },
+
+  stop: function () {
+    clearTimeout(USSAgent._timeout);
+    USSAgent._mgr = null;
+  }
+};
+
+MonitorActor.prototype._addAgent(USSAgent);
diff --git a/devtools/server/actors/moz.build b/devtools/server/actors/moz.build
new file mode 100644
index 000000000..5980876e2
--- /dev/null
+++ b/devtools/server/actors/moz.build
@@ -0,0 +1,69 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIRS += [
+    'highlighters',
+    'utils',
+]
+
+DevToolsModules(
+    'actor-registry.js',
+    'addon.js',
+    'addons.js',
+    'animation.js',
+    'breakpoint.js',
+    'call-watcher.js',
+    'canvas.js',
+    'child-process.js',
+    'childtab.js',
+    'chrome.js',
+    'common.js',
+    'css-properties.js',
+    'csscoverage.js',
+    'device.js',
+    'director-manager.js',
+    'director-registry.js',
+    'emulation.js',
+    'environment.js',
+    'errordocs.js',
+    'eventlooplag.js',
+    'frame.js',
+    'framerate.js',
+    'gcli.js',
+    'heap-snapshot-file.js',
+    'highlighters.css',
+    'highlighters.js',
+    'inspector.js',
+    'layout.js',
+    'memory.js',
+    'monitor.js',
+    'object.js',
+    'performance-entries.js',
+    'performance-recording.js',
+    'performance.js',
+    'preference.js',
+    'pretty-print-worker.js',
+    'process.js',
+    'profiler.js',
+    'promises.js',
+    'reflow.js',
+    'root.js',
+    'script.js',
+    'settings.js',
+    'source.js',
+    'storage.js',
+    'string.js',
+    'styleeditor.js',
+    'styles.js',
+    'stylesheets.js',
+    'timeline.js',
+    'webaudio.js',
+    'webbrowser.js',
+    'webconsole.js',
+    'webextension.js',
+    'webgl.js',
+    'worker.js',
+)
diff --git a/devtools/server/actors/object.js b/devtools/server/actors/object.js
new file mode 100644
index 000000000..1f417b951
--- /dev/null
+++ b/devtools/server/actors/object.js
@@ -0,0 +1,2251 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cu, Ci } = require("chrome");
+const { GeneratedLocation } = require("devtools/server/actors/common");
+const { DebuggerServer } = require("devtools/server/main");
+const DevToolsUtils = require("devtools/shared/DevToolsUtils");
+const { assert, dumpn } = DevToolsUtils;
+
+loader.lazyRequireGetter(this, "ThreadSafeChromeUtils");
+
+const TYPED_ARRAY_CLASSES = ["Uint8Array", "Uint8ClampedArray", "Uint16Array",
+      "Uint32Array", "Int8Array", "Int16Array", "Int32Array", "Float32Array",
+      "Float64Array"];
+
+// Number of items to preview in objects, arrays, maps, sets, lists,
+// collections, etc.
+const OBJECT_PREVIEW_MAX_ITEMS = 10;
+
+/**
+ * Creates an actor for the specified object.
+ *
+ * @param obj Debugger.Object
+ *        The debuggee object.
+ * @param hooks Object
+ *        A collection of abstract methods that are implemented by the caller.
+ *        ObjectActor requires the following functions to be implemented by
+ *        the caller:
+ *          - createValueGrip
+ *              Creates a value grip for the given object
+ *          - sources
+ *              TabSources getter that manages the sources of a thread
+ *          - createEnvironmentActor
+ *              Creates and return an environment actor
+ *          - getGripDepth
+ *              An actor's grip depth getter
+ *          - incrementGripDepth
+ *              Increment the actor's grip depth
+ *          - decrementGripDepth
+ *              Decrement the actor's grip depth
+ *          - globalDebugObject
+ *              The Debuggee Global Object as given by the ThreadActor
+ */
+function ObjectActor(obj, {
+  createValueGrip,
+  sources,
+  createEnvironmentActor,
+  getGripDepth,
+  incrementGripDepth,
+  decrementGripDepth,
+  getGlobalDebugObject
+}) {
+  assert(!obj.optimizedOut,
+         "Should not create object actors for optimized out values!");
+  this.obj = obj;
+  this.hooks = {
+    createValueGrip,
+    sources,
+    createEnvironmentActor,
+    getGripDepth,
+    incrementGripDepth,
+    decrementGripDepth,
+    getGlobalDebugObject
+  };
+  this.iterators = new Set();
+}
+
+ObjectActor.prototype = {
+  actorPrefix: "obj",
+
+  /**
+   * Returns a grip for this actor for returning in a protocol message.
+   */
+  grip: function () {
+    this.hooks.incrementGripDepth();
+
+    let g = {
+      "type": "object",
+      "actor": this.actorID
+    };
+
+    // If it's a proxy, lie and tell that it belongs to an invented
+    // "Proxy" class, and avoid calling the [[IsExtensible]] trap
+    if(this.obj.isProxy) {
+      g.class = "Proxy";
+      g.proxyTarget = this.hooks.createValueGrip(this.obj.proxyTarget);
+      g.proxyHandler = this.hooks.createValueGrip(this.obj.proxyHandler);
+    } else {
+      g.class = this.obj.class;
+      g.extensible = this.obj.isExtensible();
+      g.frozen = this.obj.isFrozen();
+      g.sealed = this.obj.isSealed();
+    }
+
+    if (g.class != "DeadObject") {
+      if (g.class == "Promise") {
+        g.promiseState = this._createPromiseState();
+      }
+
+      // FF40+: Allow to know how many properties an object has
+      // to lazily display them when there is a bunch.
+      // Throws on some MouseEvent object in tests.
+      try {
+        // Bug 1163520: Assert on internal functions
+        if (!["Function", "Proxy"].includes(g.class)) {
+          g.ownPropertyLength = this.obj.getOwnPropertyNames().length;
+        }
+      } catch (e) {}
+
+      let raw = this.obj.unsafeDereference();
+
+      // If Cu is not defined, we are running on a worker thread, where xrays
+      // don't exist.
+      if (Cu) {
+        raw = Cu.unwaiveXrays(raw);
+      }
+
+      if (!DevToolsUtils.isSafeJSObject(raw)) {
+        raw = null;
+      }
+
+      let previewers = DebuggerServer.ObjectActorPreviewers[g.class] ||
+                       DebuggerServer.ObjectActorPreviewers.Object;
+      for (let fn of previewers) {
+        try {
+          if (fn(this, g, raw)) {
+            break;
+          }
+        } catch (e) {
+          let msg = "ObjectActor.prototype.grip previewer function";
+          DevToolsUtils.reportException(msg, e);
+        }
+      }
+    }
+
+    this.hooks.decrementGripDepth();
+    return g;
+  },
+
+  /**
+   * Returns an object exposing the internal Promise state.
+   */
+  _createPromiseState: function () {
+    const { state, value, reason } = getPromiseState(this.obj);
+    let promiseState = { state };
+
+    if (state == "fulfilled") {
+      promiseState.value = this.hooks.createValueGrip(value);
+    } else if (state == "rejected") {
+      promiseState.reason = this.hooks.createValueGrip(reason);
+    }
+
+    promiseState.creationTimestamp = Date.now() - this.obj.promiseLifetime;
+
+    // Only add the timeToSettle property if the Promise isn't pending.
+    if (state !== "pending") {
+      promiseState.timeToSettle = this.obj.promiseTimeToResolution;
+    }
+
+    return promiseState;
+  },
+
+  /**
+   * Releases this actor from the pool.
+   */
+  release: function () {
+    if (this.registeredPool.objectActors) {
+      this.registeredPool.objectActors.delete(this.obj);
+    }
+    this.iterators.forEach(actor => this.registeredPool.removeActor(actor));
+    this.iterators.clear();
+    this.registeredPool.removeActor(this);
+  },
+
+  /**
+   * Handle a protocol request to provide the definition site of this function
+   * object.
+   */
+  onDefinitionSite: function () {
+    if (this.obj.class != "Function") {
+      return {
+        from: this.actorID,
+        error: "objectNotFunction",
+        message: this.actorID + " is not a function."
+      };
+    }
+
+    if (!this.obj.script) {
+      return {
+        from: this.actorID,
+        error: "noScript",
+        message: this.actorID + " has no Debugger.Script"
+      };
+    }
+
+    return this.hooks.sources().getOriginalLocation(new GeneratedLocation(
+      this.hooks.sources().createNonSourceMappedActor(this.obj.script.source),
+      this.obj.script.startLine,
+      0 // TODO bug 901138: use Debugger.Script.prototype.startColumn
+    )).then((originalLocation) => {
+      return {
+        source: originalLocation.originalSourceActor.form(),
+        line: originalLocation.originalLine,
+        column: originalLocation.originalColumn
+      };
+    });
+  },
+
+  /**
+   * Handle a protocol request to provide the names of the properties defined on
+   * the object and not its prototype.
+   */
+  onOwnPropertyNames: function () {
+    return { from: this.actorID,
+             ownPropertyNames: this.obj.getOwnPropertyNames() };
+  },
+
+  /**
+   * Creates an actor to iterate over an object property names and values.
+   * See PropertyIteratorActor constructor for more info about options param.
+   *
+   * @param request object
+   *        The protocol request object.
+   */
+  onEnumProperties: function (request) {
+    let actor = new PropertyIteratorActor(this, request.options);
+    this.registeredPool.addActor(actor);
+    this.iterators.add(actor);
+    return { iterator: actor.grip() };
+  },
+
+  /**
+   * Creates an actor to iterate over entries of a Map/Set-like object.
+   */
+  onEnumEntries: function () {
+    let actor = new PropertyIteratorActor(this, { enumEntries: true });
+    this.registeredPool.addActor(actor);
+    this.iterators.add(actor);
+    return { iterator: actor.grip() };
+  },
+
+  /**
+   * Handle a protocol request to provide the prototype and own properties of
+   * the object.
+   */
+  onPrototypeAndProperties: function () {
+    let ownProperties = Object.create(null);
+    let names;
+    try {
+      names = this.obj.getOwnPropertyNames();
+    } catch (ex) {
+      // The above can throw if this.obj points to a dead object.
+      // TODO: we should use Cu.isDeadWrapper() - see bug 885800.
+      return { from: this.actorID,
+               prototype: this.hooks.createValueGrip(null),
+               ownProperties: ownProperties,
+               safeGetterValues: Object.create(null) };
+    }
+    for (let name of names) {
+      ownProperties[name] = this._propertyDescriptor(name);
+    }
+    return { from: this.actorID,
+             prototype: this.hooks.createValueGrip(this.obj.proto),
+             ownProperties: ownProperties,
+             safeGetterValues: this._findSafeGetterValues(names) };
+  },
+
+  /**
+   * Find the safe getter values for the current Debugger.Object, |this.obj|.
+   *
+   * @private
+   * @param array ownProperties
+   *        The array that holds the list of known ownProperties names for
+   *        |this.obj|.
+   * @param number [limit=0]
+   *        Optional limit of getter values to find.
+   * @return object
+   *         An object that maps property names to safe getter descriptors as
+   *         defined by the remote debugging protocol.
+   */
+  _findSafeGetterValues: function (ownProperties, limit = 0) {
+    let safeGetterValues = Object.create(null);
+    let obj = this.obj;
+    let level = 0, i = 0;
+
+    // Most objects don't have any safe getters but inherit some from their
+    // prototype. Avoid calling getOwnPropertyNames on objects that may have
+    // many properties like Array, strings or js objects. That to avoid
+    // freezing firefox when doing so.
+    if (TYPED_ARRAY_CLASSES.includes(this.obj.class) ||
+        ["Array", "Object", "String"].includes(this.obj.class)) {
+      obj = obj.proto;
+      level++;
+    }
+
+    while (obj) {
+      let getters = this._findSafeGetters(obj);
+      for (let name of getters) {
+        // Avoid overwriting properties from prototypes closer to this.obj. Also
+        // avoid providing safeGetterValues from prototypes if property |name|
+        // is already defined as an own property.
+        if (name in safeGetterValues ||
+            (obj != this.obj && ownProperties.indexOf(name) !== -1)) {
+          continue;
+        }
+
+        // Ignore __proto__ on Object.prototye.
+        if (!obj.proto && name == "__proto__") {
+          continue;
+        }
+
+        let desc = null, getter = null;
+        try {
+          desc = obj.getOwnPropertyDescriptor(name);
+          getter = desc.get;
+        } catch (ex) {
+          // The above can throw if the cache becomes stale.
+        }
+        if (!getter) {
+          obj._safeGetters = null;
+          continue;
+        }
+
+        let result = getter.call(this.obj);
+        if (result && !("throw" in result)) {
+          let getterValue = undefined;
+          if ("return" in result) {
+            getterValue = result.return;
+          } else if ("yield" in result) {
+            getterValue = result.yield;
+          }
+          // WebIDL attributes specified with the LenientThis extended attribute
+          // return undefined and should be ignored.
+          if (getterValue !== undefined) {
+            safeGetterValues[name] = {
+              getterValue: this.hooks.createValueGrip(getterValue),
+              getterPrototypeLevel: level,
+              enumerable: desc.enumerable,
+              writable: level == 0 ? desc.writable : true,
+            };
+            if (limit && ++i == limit) {
+              break;
+            }
+          }
+        }
+      }
+      if (limit && i == limit) {
+        break;
+      }
+
+      obj = obj.proto;
+      level++;
+    }
+
+    return safeGetterValues;
+  },
+
+  /**
+   * Find the safe getters for a given Debugger.Object. Safe getters are native
+   * getters which are safe to execute.
+   *
+   * @private
+   * @param Debugger.Object object
+   *        The Debugger.Object where you want to find safe getters.
+   * @return Set
+   *         A Set of names of safe getters. This result is cached for each
+   *         Debugger.Object.
+   */
+  _findSafeGetters: function (object) {
+    if (object._safeGetters) {
+      return object._safeGetters;
+    }
+
+    let getters = new Set();
+    let names = [];
+    try {
+      names = object.getOwnPropertyNames();
+    } catch (ex) {
+      // Calling getOwnPropertyNames() on some wrapped native prototypes is not
+      // allowed: "cannot modify properties of a WrappedNative". See bug 952093.
+    }
+
+    for (let name of names) {
+      let desc = null;
+      try {
+        desc = object.getOwnPropertyDescriptor(name);
+      } catch (e) {
+        // Calling getOwnPropertyDescriptor on wrapped native prototypes is not
+        // allowed (bug 560072).
+      }
+      if (!desc || desc.value !== undefined || !("get" in desc)) {
+        continue;
+      }
+
+      if (DevToolsUtils.hasSafeGetter(desc)) {
+        getters.add(name);
+      }
+    }
+
+    object._safeGetters = getters;
+    return getters;
+  },
+
+  /**
+   * Handle a protocol request to provide the prototype of the object.
+   */
+  onPrototype: function () {
+    return { from: this.actorID,
+             prototype: this.hooks.createValueGrip(this.obj.proto) };
+  },
+
+  /**
+   * Handle a protocol request to provide the property descriptor of the
+   * object's specified property.
+   *
+   * @param request object
+   *        The protocol request object.
+   */
+  onProperty: function (request) {
+    if (!request.name) {
+      return { error: "missingParameter",
+               message: "no property name was specified" };
+    }
+
+    return { from: this.actorID,
+             descriptor: this._propertyDescriptor(request.name) };
+  },
+
+  /**
+   * Handle a protocol request to provide the display string for the object.
+   */
+  onDisplayString: function () {
+    const string = stringify(this.obj);
+    return { from: this.actorID,
+             displayString: this.hooks.createValueGrip(string) };
+  },
+
+  /**
+   * A helper method that creates a property descriptor for the provided object,
+   * properly formatted for sending in a protocol response.
+   *
+   * @private
+   * @param string name
+   *        The property that the descriptor is generated for.
+   * @param boolean [onlyEnumerable]
+   *        Optional: true if you want a descriptor only for an enumerable
+   *        property, false otherwise.
+   * @return object|undefined
+   *         The property descriptor, or undefined if this is not an enumerable
+   *         property and onlyEnumerable=true.
+   */
+  _propertyDescriptor: function (name, onlyEnumerable) {
+    let desc;
+    try {
+      desc = this.obj.getOwnPropertyDescriptor(name);
+    } catch (e) {
+      // Calling getOwnPropertyDescriptor on wrapped native prototypes is not
+      // allowed (bug 560072). Inform the user with a bogus, but hopefully
+      // explanatory, descriptor.
+      return {
+        configurable: false,
+        writable: false,
+        enumerable: false,
+        value: e.name
+      };
+    }
+
+    if (!desc || onlyEnumerable && !desc.enumerable) {
+      return undefined;
+    }
+
+    let retval = {
+      configurable: desc.configurable,
+      enumerable: desc.enumerable
+    };
+
+    if ("value" in desc) {
+      retval.writable = desc.writable;
+      retval.value = this.hooks.createValueGrip(desc.value);
+    } else {
+      if ("get" in desc) {
+        retval.get = this.hooks.createValueGrip(desc.get);
+      }
+      if ("set" in desc) {
+        retval.set = this.hooks.createValueGrip(desc.set);
+      }
+    }
+    return retval;
+  },
+
+  /**
+   * Handle a protocol request to provide the source code of a function.
+   *
+   * @param request object
+   *        The protocol request object.
+   */
+  onDecompile: function (request) {
+    if (this.obj.class !== "Function") {
+      return { error: "objectNotFunction",
+               message: "decompile request is only valid for object grips " +
+                        "with a 'Function' class." };
+    }
+
+    return { from: this.actorID,
+             decompiledCode: this.obj.decompile(!!request.pretty) };
+  },
+
+  /**
+   * Handle a protocol request to provide the parameters of a function.
+   */
+  onParameterNames: function () {
+    if (this.obj.class !== "Function") {
+      return { error: "objectNotFunction",
+               message: "'parameterNames' request is only valid for object " +
+                        "grips with a 'Function' class." };
+    }
+
+    return { parameterNames: this.obj.parameterNames };
+  },
+
+  /**
+   * Handle a protocol request to release a thread-lifetime grip.
+   */
+  onRelease: function () {
+    this.release();
+    return {};
+  },
+
+  /**
+   * Handle a protocol request to provide the lexical scope of a function.
+   */
+  onScope: function () {
+    if (this.obj.class !== "Function") {
+      return { error: "objectNotFunction",
+               message: "scope request is only valid for object grips with a" +
+                        " 'Function' class." };
+    }
+
+    let envActor = this.hooks.createEnvironmentActor(this.obj.environment,
+                                                     this.registeredPool);
+    if (!envActor) {
+      return { error: "notDebuggee",
+               message: "cannot access the environment of this function." };
+    }
+
+    return { from: this.actorID, scope: envActor.form() };
+  },
+
+  /**
+   * Handle a protocol request to get the list of dependent promises of a
+   * promise.
+   *
+   * @return object
+   *         Returns an object containing an array of object grips of the
+   *         dependent promises
+   */
+  onDependentPromises: function () {
+    if (this.obj.class != "Promise") {
+      return { error: "objectNotPromise",
+               message: "'dependentPromises' request is only valid for " +
+                        "object grips with a 'Promise' class." };
+    }
+
+    let promises = this.obj.promiseDependentPromises.map(p => this.hooks.createValueGrip(p));
+
+    return { promises };
+  },
+
+  /**
+   * Handle a protocol request to get the allocation stack of a promise.
+   */
+  onAllocationStack: function () {
+    if (this.obj.class != "Promise") {
+      return { error: "objectNotPromise",
+               message: "'allocationStack' request is only valid for " +
+                        "object grips with a 'Promise' class." };
+    }
+
+    let stack = this.obj.promiseAllocationSite;
+    let allocationStacks = [];
+
+    while (stack) {
+      if (stack.source) {
+        let source = this._getSourceOriginalLocation(stack);
+
+        if (source) {
+          allocationStacks.push(source);
+        }
+      }
+      stack = stack.parent;
+    }
+
+    return Promise.all(allocationStacks).then(stacks => {
+      return { allocationStack: stacks };
+    });
+  },
+
+  /**
+   * Handle a protocol request to get the fulfillment stack of a promise.
+   */
+  onFulfillmentStack: function () {
+    if (this.obj.class != "Promise") {
+      return { error: "objectNotPromise",
+               message: "'fulfillmentStack' request is only valid for " +
+                        "object grips with a 'Promise' class." };
+    }
+
+    let stack = this.obj.promiseResolutionSite;
+    let fulfillmentStacks = [];
+
+    while (stack) {
+      if (stack.source) {
+        let source = this._getSourceOriginalLocation(stack);
+
+        if (source) {
+          fulfillmentStacks.push(source);
+        }
+      }
+      stack = stack.parent;
+    }
+
+    return Promise.all(fulfillmentStacks).then(stacks => {
+      return { fulfillmentStack: stacks };
+    });
+  },
+
+  /**
+   * Handle a protocol request to get the rejection stack of a promise.
+   */
+  onRejectionStack: function () {
+    if (this.obj.class != "Promise") {
+      return { error: "objectNotPromise",
+               message: "'rejectionStack' request is only valid for " +
+                        "object grips with a 'Promise' class." };
+    }
+
+    let stack = this.obj.promiseResolutionSite;
+    let rejectionStacks = [];
+
+    while (stack) {
+      if (stack.source) {
+        let source = this._getSourceOriginalLocation(stack);
+
+        if (source) {
+          rejectionStacks.push(source);
+        }
+      }
+      stack = stack.parent;
+    }
+
+    return Promise.all(rejectionStacks).then(stacks => {
+      return { rejectionStack: stacks };
+    });
+  },
+
+  /**
+   * Helper function for fetching the source location of a SavedFrame stack.
+   *
+   * @param SavedFrame stack
+   *        The promise allocation stack frame
+   * @return object
+   *         Returns an object containing the source location of the SavedFrame
+   *         stack.
+   */
+  _getSourceOriginalLocation: function (stack) {
+    let source;
+
+    // Catch any errors if the source actor cannot be found
+    try {
+      source = this.hooks.sources().getSourceActorByURL(stack.source);
+    } catch (e) {}
+
+    if (!source) {
+      return null;
+    }
+
+    return this.hooks.sources().getOriginalLocation(new GeneratedLocation(
+      source,
+      stack.line,
+      stack.column
+    )).then((originalLocation) => {
+      return {
+        source: originalLocation.originalSourceActor.form(),
+        line: originalLocation.originalLine,
+        column: originalLocation.originalColumn,
+        functionDisplayName: stack.functionDisplayName
+      };
+    });
+  }
+};
+
+ObjectActor.prototype.requestTypes = {
+  "definitionSite": ObjectActor.prototype.onDefinitionSite,
+  "parameterNames": ObjectActor.prototype.onParameterNames,
+  "prototypeAndProperties": ObjectActor.prototype.onPrototypeAndProperties,
+  "enumProperties": ObjectActor.prototype.onEnumProperties,
+  "prototype": ObjectActor.prototype.onPrototype,
+  "property": ObjectActor.prototype.onProperty,
+  "displayString": ObjectActor.prototype.onDisplayString,
+  "ownPropertyNames": ObjectActor.prototype.onOwnPropertyNames,
+  "decompile": ObjectActor.prototype.onDecompile,
+  "release": ObjectActor.prototype.onRelease,
+  "scope": ObjectActor.prototype.onScope,
+  "dependentPromises": ObjectActor.prototype.onDependentPromises,
+  "allocationStack": ObjectActor.prototype.onAllocationStack,
+  "fulfillmentStack": ObjectActor.prototype.onFulfillmentStack,
+  "rejectionStack": ObjectActor.prototype.onRejectionStack,
+  "enumEntries": ObjectActor.prototype.onEnumEntries,
+};
+
+/**
+ * Creates an actor to iterate over an object's property names and values.
+ *
+ * @param objectActor ObjectActor
+ *        The object actor.
+ * @param options Object
+ *        A dictionary object with various boolean attributes:
+ *        - enumEntries Boolean
+ *          If true, enumerates the entries of a Map or Set object
+ *          instead of enumerating properties.
+ *        - ignoreIndexedProperties Boolean
+ *          If true, filters out Array items.
+ *          e.g. properties names between `0` and `object.length`.
+ *        - ignoreNonIndexedProperties Boolean
+ *          If true, filters out items that aren't array items
+ *          e.g. properties names that are not a number between `0`
+ *          and `object.length`.
+ *        - sort Boolean
+ *          If true, the iterator will sort the properties by name
+ *          before dispatching them.
+ *        - query String
+ *          If non-empty, will filter the properties by names and values
+ *          containing this query string. The match is not case-sensitive.
+ *          Regarding value filtering it just compare to the stringification
+ *          of the property value.
+ */
+function PropertyIteratorActor(objectActor, options) {
+  if (options.enumEntries) {
+    let cls = objectActor.obj.class;
+    if (cls == "Map") {
+      this.iterator = enumMapEntries(objectActor);
+    } else if (cls == "WeakMap") {
+      this.iterator = enumWeakMapEntries(objectActor);
+    } else if (cls == "Set") {
+      this.iterator = enumSetEntries(objectActor);
+    } else if (cls == "WeakSet") {
+      this.iterator = enumWeakSetEntries(objectActor);
+    } else {
+      throw new Error("Unsupported class to enumerate entries from: " + cls);
+    }
+  } else if (options.ignoreNonIndexedProperties && !options.query) {
+    this.iterator = enumArrayProperties(objectActor, options);
+  } else {
+    this.iterator = enumObjectProperties(objectActor, options);
+  }
+}
+
+PropertyIteratorActor.prototype = {
+  actorPrefix: "propertyIterator",
+
+  grip() {
+    return {
+      type: this.actorPrefix,
+      actor: this.actorID,
+      count: this.iterator.size
+    };
+  },
+
+  names({ indexes }) {
+    let list = [];
+    for (let idx of indexes) {
+      list.push(this.iterator.propertyName(idx));
+    }
+    return {
+      names: indexes
+    };
+  },
+
+  slice({ start, count }) {
+    let ownProperties = Object.create(null);
+    for (let i = start, m = start + count; i < m; i++) {
+      let name = this.iterator.propertyName(i);
+      ownProperties[name] = this.iterator.propertyDescription(i);
+    }
+    return {
+      ownProperties
+    };
+  },
+
+  all() {
+    return this.slice({ start: 0, count: this.length });
+  }
+};
+
+PropertyIteratorActor.prototype.requestTypes = {
+  "names": PropertyIteratorActor.prototype.names,
+  "slice": PropertyIteratorActor.prototype.slice,
+  "all": PropertyIteratorActor.prototype.all,
+};
+
+function enumArrayProperties(objectActor, options) {
+  let length = DevToolsUtils.getProperty(objectActor.obj, "length");
+  if (typeof length !== "number") {
+    // Pseudo arrays are flagged as ArrayLike if they have
+    // subsequent indexed properties without having any length attribute.
+    length = 0;
+    let names = objectActor.obj.getOwnPropertyNames();
+    for (let key of names) {
+      if (isNaN(key) || key != length++) {
+        break;
+      }
+    }
+  }
+
+  return {
+    size: length,
+    propertyName(index) {
+      return index;
+    },
+    propertyDescription(index) {
+      return objectActor._propertyDescriptor(index);
+    }
+  };
+}
+
+function enumObjectProperties(objectActor, options) {
+  let names = [];
+  try {
+    names = objectActor.obj.getOwnPropertyNames();
+  } catch (ex) {
+    // Calling getOwnPropertyNames() on some wrapped native prototypes is not
+    // allowed: "cannot modify properties of a WrappedNative". See bug 952093.
+  }
+
+  if (options.ignoreNonIndexedProperties || options.ignoreIndexedProperties) {
+    let length = DevToolsUtils.getProperty(objectActor.obj, "length");
+    if (typeof length !== "number") {
+      // Pseudo arrays are flagged as ArrayLike if they have
+      // subsequent indexed properties without having any length attribute.
+      length = 0;
+      for (let key of names) {
+        if (isNaN(key) || key != length++) {
+          break;
+        }
+      }
+    }
+
+    // It appears that getOwnPropertyNames always returns indexed properties
+    // first, so we can safely slice `names` for/against indexed properties.
+    // We do such clever operation to optimize very large array inspection,
+    // like webaudio buffers.
+    if (options.ignoreIndexedProperties) {
+      // Keep items after `length` index
+      names = names.slice(length);
+    } else if (options.ignoreNonIndexedProperties) {
+      // Remove `length` first items
+      names.splice(length);
+    }
+  }
+
+  let safeGetterValues = objectActor._findSafeGetterValues(names, 0);
+  let safeGetterNames = Object.keys(safeGetterValues);
+  // Merge the safe getter values into the existing properties list.
+  for (let name of safeGetterNames) {
+    if (!names.includes(name)) {
+      names.push(name);
+    }
+  }
+
+  if (options.query) {
+    let { query } = options;
+    query = query.toLowerCase();
+    names = names.filter(name => {
+      // Filter on attribute names
+      if (name.toLowerCase().includes(query)) {
+        return true;
+      }
+      // and then on attribute values
+      let desc;
+      try {
+        desc = objectActor.obj.getOwnPropertyDescriptor(name);
+      } catch (e) {
+        // Calling getOwnPropertyDescriptor on wrapped native prototypes is not
+        // allowed (bug 560072).
+      }
+      if (desc && desc.value &&
+          String(desc.value).includes(query)) {
+        return true;
+      }
+      return false;
+    });
+  }
+
+  if (options.sort) {
+    names.sort();
+  }
+
+  return {
+    size: names.length,
+    propertyName(index) {
+      return names[index];
+    },
+    propertyDescription(index) {
+      let name = names[index];
+      let desc = objectActor._propertyDescriptor(name);
+      if (!desc) {
+        desc = safeGetterValues[name];
+      } else if (name in safeGetterValues) {
+        // Merge the safe getter values into the existing properties list.
+        let { getterValue, getterPrototypeLevel } = safeGetterValues[name];
+        desc.getterValue = getterValue;
+        desc.getterPrototypeLevel = getterPrototypeLevel;
+      }
+      return desc;
+    }
+  };
+}
+
+/**
+ * Helper function to create a grip from a Map/Set entry
+ */
+function gripFromEntry({ obj, hooks }, entry) {
+  return hooks.createValueGrip(
+    makeDebuggeeValueIfNeeded(obj, Cu.unwaiveXrays(entry)));
+}
+
+function enumMapEntries(objectActor) {
+  // Iterating over a Map via .entries goes through various intermediate
+  // objects - an Iterator object, then a 2-element Array object, then the
+  // actual values we care about. We don't have Xrays to Iterator objects,
+  // so we get Opaque wrappers for them. And even though we have Xrays to
+  // Arrays, the semantics often deny access to the entires based on the
+  // nature of the values. So we need waive Xrays for the iterator object
+  // and the tupes, and then re-apply them on the underlying values until
+  // we fix bug 1023984.
+  //
+  // Even then though, we might want to continue waiving Xrays here for the
+  // same reason we do so for Arrays above - this filtering behavior is likely
+  // to be more confusing than beneficial in the case of Object previews.
+  let raw = objectActor.obj.unsafeDereference();
+
+  let keys = [...Cu.waiveXrays(Map.prototype.keys.call(raw))];
+  return {
+    [Symbol.iterator]: function* () {
+      for (let key of keys) {
+        let value = Map.prototype.get.call(raw, key);
+        yield [ key, value ].map(val => gripFromEntry(objectActor, val));
+      }
+    },
+    size: keys.length,
+    propertyName(index) {
+      return index;
+    },
+    propertyDescription(index) {
+      let key = keys[index];
+      let val = Map.prototype.get.call(raw, key);
+      return {
+        enumerable: true,
+        value: {
+          type: "mapEntry",
+          preview: {
+            key: gripFromEntry(objectActor, key),
+            value: gripFromEntry(objectActor, val)
+          }
+        }
+      };
+    }
+  };
+}
+
+function enumWeakMapEntries(objectActor) {
+  // We currently lack XrayWrappers for WeakMap, so when we iterate over
+  // the values, the temporary iterator objects get created in the target
+  // compartment. However, we _do_ have Xrays to Object now, so we end up
+  // Xraying those temporary objects, and filtering access to |it.value|
+  // based on whether or not it's Xrayable and/or callable, which breaks
+  // the for/of iteration.
+  //
+  // This code is designed to handle untrusted objects, so we can safely
+  // waive Xrays on the iterable, and relying on the Debugger machinery to
+  // make sure we handle the resulting objects carefully.
+  let raw = objectActor.obj.unsafeDereference();
+  let keys = Cu.waiveXrays(
+    ThreadSafeChromeUtils.nondeterministicGetWeakMapKeys(raw));
+
+  return {
+    [Symbol.iterator]: function* () {
+      for (let key of keys) {
+        let value = WeakMap.prototype.get.call(raw, key);
+        yield [ key, value ].map(val => gripFromEntry(objectActor, val));
+      }
+    },
+    size: keys.length,
+    propertyName(index) {
+      return index;
+    },
+    propertyDescription(index) {
+      let key = keys[index];
+      let val = WeakMap.prototype.get.call(raw, key);
+      return {
+        enumerable: true,
+        value: {
+          type: "mapEntry",
+          preview: {
+            key: gripFromEntry(objectActor, key),
+            value: gripFromEntry(objectActor, val)
+          }
+        }
+      };
+    }
+  };
+}
+
+function enumSetEntries(objectActor) {
+  // We currently lack XrayWrappers for Set, so when we iterate over
+  // the values, the temporary iterator objects get created in the target
+  // compartment. However, we _do_ have Xrays to Object now, so we end up
+  // Xraying those temporary objects, and filtering access to |it.value|
+  // based on whether or not it's Xrayable and/or callable, which breaks
+  // the for/of iteration.
+  //
+  // This code is designed to handle untrusted objects, so we can safely
+  // waive Xrays on the iterable, and relying on the Debugger machinery to
+  // make sure we handle the resulting objects carefully.
+  let raw = objectActor.obj.unsafeDereference();
+  let values = [...Cu.waiveXrays(Set.prototype.values.call(raw))];
+
+  return {
+    [Symbol.iterator]: function* () {
+      for (let item of values) {
+        yield gripFromEntry(objectActor, item);
+      }
+    },
+    size: values.length,
+    propertyName(index) {
+      return index;
+    },
+    propertyDescription(index) {
+      let val = values[index];
+      return {
+        enumerable: true,
+        value: gripFromEntry(objectActor, val)
+      };
+    }
+  };
+}
+
+function enumWeakSetEntries(objectActor) {
+  // We currently lack XrayWrappers for WeakSet, so when we iterate over
+  // the values, the temporary iterator objects get created in the target
+  // compartment. However, we _do_ have Xrays to Object now, so we end up
+  // Xraying those temporary objects, and filtering access to |it.value|
+  // based on whether or not it's Xrayable and/or callable, which breaks
+  // the for/of iteration.
+  //
+  // This code is designed to handle untrusted objects, so we can safely
+  // waive Xrays on the iterable, and relying on the Debugger machinery to
+  // make sure we handle the resulting objects carefully.
+  let raw = objectActor.obj.unsafeDereference();
+  let keys = Cu.waiveXrays(
+    ThreadSafeChromeUtils.nondeterministicGetWeakSetKeys(raw));
+
+  return {
+    [Symbol.iterator]: function* () {
+      for (let item of keys) {
+        yield gripFromEntry(objectActor, item);
+      }
+    },
+    size: keys.length,
+    propertyName(index) {
+      return index;
+    },
+    propertyDescription(index) {
+      let val = keys[index];
+      return {
+        enumerable: true,
+        value: gripFromEntry(objectActor, val)
+      };
+    }
+  };
+}
+
+/**
+ * Functions for adding information to ObjectActor grips for the purpose of
+ * having customized output. This object holds arrays mapped by
+ * Debugger.Object.prototype.class.
+ *
+ * In each array you can add functions that take three
+ * arguments:
+ *   - the ObjectActor instance and its hooks to make a preview for,
+ *   - the grip object being prepared for the client,
+ *   - the raw JS object after calling Debugger.Object.unsafeDereference(). This
+ *   argument is only provided if the object is safe for reading properties and
+ *   executing methods. See DevToolsUtils.isSafeJSObject().
+ *
+ * Functions must return false if they cannot provide preview
+ * information for the debugger object, or true otherwise.
+ */
+DebuggerServer.ObjectActorPreviewers = {
+  String: [function (objectActor, grip, rawObj) {
+    return wrappedPrimitivePreviewer("String", String, objectActor, grip, rawObj);
+  }],
+
+  Boolean: [function (objectActor, grip, rawObj) {
+    return wrappedPrimitivePreviewer("Boolean", Boolean, objectActor, grip, rawObj);
+  }],
+
+  Number: [function (objectActor, grip, rawObj) {
+    return wrappedPrimitivePreviewer("Number", Number, objectActor, grip, rawObj);
+  }],
+
+  Function: [function ({obj, hooks}, grip) {
+    if (obj.name) {
+      grip.name = obj.name;
+    }
+
+    if (obj.displayName) {
+      grip.displayName = obj.displayName.substr(0, 500);
+    }
+
+    if (obj.parameterNames) {
+      grip.parameterNames = obj.parameterNames;
+    }
+
+    // Check if the developer has added a de-facto standard displayName
+    // property for us to use.
+    let userDisplayName;
+    try {
+      userDisplayName = obj.getOwnPropertyDescriptor("displayName");
+    } catch (e) {
+      // Calling getOwnPropertyDescriptor with displayName might throw
+      // with "permission denied" errors for some functions.
+      dumpn(e);
+    }
+
+    if (userDisplayName && typeof userDisplayName.value == "string" &&
+        userDisplayName.value) {
+      grip.userDisplayName = hooks.createValueGrip(userDisplayName.value);
+    }
+
+    let dbgGlobal = hooks.getGlobalDebugObject();
+    if (dbgGlobal) {
+      let script = dbgGlobal.makeDebuggeeValue(obj.unsafeDereference()).script;
+      if (script) {
+        grip.location = {
+          url: script.url,
+          line: script.startLine
+        };
+      }
+    }
+
+    return true;
+  }],
+
+  RegExp: [function ({obj, hooks}, grip) {
+    // Avoid having any special preview for the RegExp.prototype itself.
+    if (!obj.proto || obj.proto.class != "RegExp") {
+      return false;
+    }
+
+    let str = RegExp.prototype.toString.call(obj.unsafeDereference());
+    grip.displayString = hooks.createValueGrip(str);
+    return true;
+  }],
+
+  Date: [function ({obj, hooks}, grip) {
+    let time = Date.prototype.getTime.call(obj.unsafeDereference());
+
+    grip.preview = {
+      timestamp: hooks.createValueGrip(time),
+    };
+    return true;
+  }],
+
+  Array: [function ({obj, hooks}, grip) {
+    let length = DevToolsUtils.getProperty(obj, "length");
+    if (typeof length != "number") {
+      return false;
+    }
+
+    grip.preview = {
+      kind: "ArrayLike",
+      length: length,
+    };
+
+    if (hooks.getGripDepth() > 1) {
+      return true;
+    }
+
+    let raw = obj.unsafeDereference();
+    let items = grip.preview.items = [];
+
+    for (let i = 0; i < length; ++i) {
+      // Array Xrays filter out various possibly-unsafe properties (like
+      // functions, and claim that the value is undefined instead. This
+      // is generally the right thing for privileged code accessing untrusted
+      // objects, but quite confusing for Object previews. So we manually
+      // override this protection by waiving Xrays on the array, and re-applying
+      // Xrays on any indexed value props that we pull off of it.
+      let desc = Object.getOwnPropertyDescriptor(Cu.waiveXrays(raw), i);
+      if (desc && !desc.get && !desc.set) {
+        let value = Cu.unwaiveXrays(desc.value);
+        value = makeDebuggeeValueIfNeeded(obj, value);
+        items.push(hooks.createValueGrip(value));
+      } else {
+        items.push(null);
+      }
+
+      if (items.length == OBJECT_PREVIEW_MAX_ITEMS) {
+        break;
+      }
+    }
+
+    return true;
+  }],
+
+  Set: [function (objectActor, grip) {
+    let size = DevToolsUtils.getProperty(objectActor.obj, "size");
+    if (typeof size != "number") {
+      return false;
+    }
+
+    grip.preview = {
+      kind: "ArrayLike",
+      length: size,
+    };
+
+    // Avoid recursive object grips.
+    if (objectActor.hooks.getGripDepth() > 1) {
+      return true;
+    }
+
+    let items = grip.preview.items = [];
+    for (let item of enumSetEntries(objectActor)) {
+      items.push(item);
+      if (items.length == OBJECT_PREVIEW_MAX_ITEMS) {
+        break;
+      }
+    }
+
+    return true;
+  }],
+
+  WeakSet: [function (objectActor, grip) {
+    let enumEntries = enumWeakSetEntries(objectActor);
+
+    grip.preview = {
+      kind: "ArrayLike",
+      length: enumEntries.size
+    };
+
+    // Avoid recursive object grips.
+    if (objectActor.hooks.getGripDepth() > 1) {
+      return true;
+    }
+
+    let items = grip.preview.items = [];
+    for (let item of enumEntries) {
+      items.push(item);
+      if (items.length == OBJECT_PREVIEW_MAX_ITEMS) {
+        break;
+      }
+    }
+
+    return true;
+  }],
+
+  Map: [function (objectActor, grip) {
+    let size = DevToolsUtils.getProperty(objectActor.obj, "size");
+    if (typeof size != "number") {
+      return false;
+    }
+
+    grip.preview = {
+      kind: "MapLike",
+      size: size,
+    };
+
+    if (objectActor.hooks.getGripDepth() > 1) {
+      return true;
+    }
+
+    let entries = grip.preview.entries = [];
+    for (let entry of enumMapEntries(objectActor)) {
+      entries.push(entry);
+      if (entries.length == OBJECT_PREVIEW_MAX_ITEMS) {
+        break;
+      }
+    }
+
+    return true;
+  }],
+
+  WeakMap: [function (objectActor, grip) {
+    let enumEntries = enumWeakMapEntries(objectActor);
+
+    grip.preview = {
+      kind: "MapLike",
+      size: enumEntries.size
+    };
+
+    if (objectActor.hooks.getGripDepth() > 1) {
+      return true;
+    }
+
+    let entries = grip.preview.entries = [];
+    for (let entry of enumEntries) {
+      entries.push(entry);
+      if (entries.length == OBJECT_PREVIEW_MAX_ITEMS) {
+        break;
+      }
+    }
+
+    return true;
+  }],
+
+  DOMStringMap: [function ({obj, hooks}, grip, rawObj) {
+    if (!rawObj) {
+      return false;
+    }
+
+    let keys = obj.getOwnPropertyNames();
+    grip.preview = {
+      kind: "MapLike",
+      size: keys.length,
+    };
+
+    if (hooks.getGripDepth() > 1) {
+      return true;
+    }
+
+    let entries = grip.preview.entries = [];
+    for (let key of keys) {
+      let value = makeDebuggeeValueIfNeeded(obj, rawObj[key]);
+      entries.push([key, hooks.createValueGrip(value)]);
+      if (entries.length == OBJECT_PREVIEW_MAX_ITEMS) {
+        break;
+      }
+    }
+
+    return true;
+  }],
+
+  Proxy: [function ({obj, hooks}, grip, rawObj) {
+    grip.preview = {
+      kind: "Object",
+      ownProperties: Object.create(null),
+      ownPropertiesLength: 2
+    };
+
+    if (hooks.getGripDepth() > 1) {
+      return true;
+    }
+
+    grip.preview.ownProperties['<target>'] = {value: grip.proxyTarget};
+    grip.preview.ownProperties['<handler>'] = {value: grip.proxyHandler};
+
+    return true;
+  }],
+};
+
+/**
+ * Generic previewer for classes wrapping primitives, like String,
+ * Number and Boolean.
+ *
+ * @param string className
+ *        Class name to expect.
+ * @param object classObj
+ *        The class to expect, eg. String. The valueOf() method of the class is
+ *        invoked on the given object.
+ * @param ObjectActor objectActor
+ *        The object actor
+ * @param Object grip
+ *        The result grip to fill in
+ * @return Booolean true if the object was handled, false otherwise
+ */
+function wrappedPrimitivePreviewer(className, classObj, objectActor, grip, rawObj) {
+  let {obj, hooks} = objectActor;
+
+  if (!obj.proto || obj.proto.class != className) {
+    return false;
+  }
+
+  let v = null;
+  try {
+    v = classObj.prototype.valueOf.call(rawObj);
+  } catch (ex) {
+    // valueOf() can throw if the raw JS object is "misbehaved".
+    return false;
+  }
+
+  if (v === null) {
+    return false;
+  }
+
+  let canHandle = GenericObject(objectActor, grip, rawObj, className === "String");
+  if (!canHandle) {
+    return false;
+  }
+
+  grip.preview.wrappedValue =
+    hooks.createValueGrip(makeDebuggeeValueIfNeeded(obj, v));
+  return true;
+}
+
+function GenericObject(objectActor, grip, rawObj, specialStringBehavior = false) {
+  let {obj, hooks} = objectActor;
+  if (grip.preview || grip.displayString || hooks.getGripDepth() > 1) {
+    return false;
+  }
+
+  let i = 0, names = [];
+  let preview = grip.preview = {
+    kind: "Object",
+    ownProperties: Object.create(null),
+  };
+
+  try {
+    names = obj.getOwnPropertyNames();
+  } catch (ex) {
+    // Calling getOwnPropertyNames() on some wrapped native prototypes is not
+    // allowed: "cannot modify properties of a WrappedNative". See bug 952093.
+  }
+
+  preview.ownPropertiesLength = names.length;
+
+  let length;
+  if (specialStringBehavior) {
+    length = DevToolsUtils.getProperty(obj, "length");
+    if (typeof length != "number") {
+      specialStringBehavior = false;
+    }
+  }
+
+  for (let name of names) {
+    if (specialStringBehavior && /^[0-9]+$/.test(name)) {
+      let num = parseInt(name, 10);
+      if (num.toString() === name && num >= 0 && num < length) {
+        continue;
+      }
+    }
+
+    let desc = objectActor._propertyDescriptor(name, true);
+    if (!desc) {
+      continue;
+    }
+
+    preview.ownProperties[name] = desc;
+    if (++i == OBJECT_PREVIEW_MAX_ITEMS) {
+      break;
+    }
+  }
+
+  if (i < OBJECT_PREVIEW_MAX_ITEMS) {
+    preview.safeGetterValues = objectActor._findSafeGetterValues(
+      Object.keys(preview.ownProperties),
+      OBJECT_PREVIEW_MAX_ITEMS - i);
+  }
+
+  return true;
+}
+
+// Preview functions that do not rely on the object class.
+DebuggerServer.ObjectActorPreviewers.Object = [
+  function TypedArray({obj, hooks}, grip) {
+    if (TYPED_ARRAY_CLASSES.indexOf(obj.class) == -1) {
+      return false;
+    }
+
+    let length = DevToolsUtils.getProperty(obj, "length");
+    if (typeof length != "number") {
+      return false;
+    }
+
+    grip.preview = {
+      kind: "ArrayLike",
+      length: length,
+    };
+
+    if (hooks.getGripDepth() > 1) {
+      return true;
+    }
+
+    let raw = obj.unsafeDereference();
+    let global = Cu.getGlobalForObject(DebuggerServer);
+    let classProto = global[obj.class].prototype;
+    // The Xray machinery for TypedArrays denies indexed access on the grounds
+    // that it's slow, and advises callers to do a structured clone instead.
+    let safeView = Cu.cloneInto(classProto.subarray.call(raw, 0,
+      OBJECT_PREVIEW_MAX_ITEMS), global);
+    let items = grip.preview.items = [];
+    for (let i = 0; i < safeView.length; i++) {
+      items.push(safeView[i]);
+    }
+
+    return true;
+  },
+
+  function Error({obj, hooks}, grip) {
+    switch (obj.class) {
+      case "Error":
+      case "EvalError":
+      case "RangeError":
+      case "ReferenceError":
+      case "SyntaxError":
+      case "TypeError":
+      case "URIError":
+        let name = DevToolsUtils.getProperty(obj, "name");
+        let msg = DevToolsUtils.getProperty(obj, "message");
+        let stack = DevToolsUtils.getProperty(obj, "stack");
+        let fileName = DevToolsUtils.getProperty(obj, "fileName");
+        let lineNumber = DevToolsUtils.getProperty(obj, "lineNumber");
+        let columnNumber = DevToolsUtils.getProperty(obj, "columnNumber");
+        grip.preview = {
+          kind: "Error",
+          name: hooks.createValueGrip(name),
+          message: hooks.createValueGrip(msg),
+          stack: hooks.createValueGrip(stack),
+          fileName: hooks.createValueGrip(fileName),
+          lineNumber: hooks.createValueGrip(lineNumber),
+          columnNumber: hooks.createValueGrip(columnNumber),
+        };
+        return true;
+      default:
+        return false;
+    }
+  },
+
+  function CSSMediaRule({obj, hooks}, grip, rawObj) {
+    if (isWorker || !rawObj || !(rawObj instanceof Ci.nsIDOMCSSMediaRule)) {
+      return false;
+    }
+    grip.preview = {
+      kind: "ObjectWithText",
+      text: hooks.createValueGrip(rawObj.conditionText),
+    };
+    return true;
+  },
+
+  function CSSStyleRule({obj, hooks}, grip, rawObj) {
+    if (isWorker || !rawObj || !(rawObj instanceof Ci.nsIDOMCSSStyleRule)) {
+      return false;
+    }
+    grip.preview = {
+      kind: "ObjectWithText",
+      text: hooks.createValueGrip(rawObj.selectorText),
+    };
+    return true;
+  },
+
+  function ObjectWithURL({obj, hooks}, grip, rawObj) {
+    if (isWorker || !rawObj || !(rawObj instanceof Ci.nsIDOMCSSImportRule ||
+                                 rawObj instanceof Ci.nsIDOMCSSStyleSheet ||
+                                 rawObj instanceof Ci.nsIDOMLocation ||
+                                 rawObj instanceof Ci.nsIDOMWindow)) {
+      return false;
+    }
+
+    let url;
+    if (rawObj instanceof Ci.nsIDOMWindow && rawObj.location) {
+      url = rawObj.location.href;
+    } else if (rawObj.href) {
+      url = rawObj.href;
+    } else {
+      return false;
+    }
+
+    grip.preview = {
+      kind: "ObjectWithURL",
+      url: hooks.createValueGrip(url),
+    };
+
+    return true;
+  },
+
+  function ArrayLike({obj, hooks}, grip, rawObj) {
+    if (isWorker || !rawObj ||
+        obj.class != "DOMStringList" &&
+        obj.class != "DOMTokenList" &&
+        !(rawObj instanceof Ci.nsIDOMMozNamedAttrMap ||
+          rawObj instanceof Ci.nsIDOMCSSRuleList ||
+          rawObj instanceof Ci.nsIDOMCSSValueList ||
+          rawObj instanceof Ci.nsIDOMFileList ||
+          rawObj instanceof Ci.nsIDOMFontFaceList ||
+          rawObj instanceof Ci.nsIDOMMediaList ||
+          rawObj instanceof Ci.nsIDOMNodeList ||
+          rawObj instanceof Ci.nsIDOMStyleSheetList)) {
+      return false;
+    }
+
+    if (typeof rawObj.length != "number") {
+      return false;
+    }
+
+    grip.preview = {
+      kind: "ArrayLike",
+      length: rawObj.length,
+    };
+
+    if (hooks.getGripDepth() > 1) {
+      return true;
+    }
+
+    let items = grip.preview.items = [];
+
+    for (let i = 0; i < rawObj.length &&
+                    items.length < OBJECT_PREVIEW_MAX_ITEMS; i++) {
+      let value = makeDebuggeeValueIfNeeded(obj, rawObj[i]);
+      items.push(hooks.createValueGrip(value));
+    }
+
+    return true;
+  },
+
+  function CSSStyleDeclaration({obj, hooks}, grip, rawObj) {
+    if (isWorker || !rawObj ||
+        !(rawObj instanceof Ci.nsIDOMCSSStyleDeclaration)) {
+      return false;
+    }
+
+    grip.preview = {
+      kind: "MapLike",
+      size: rawObj.length,
+    };
+
+    let entries = grip.preview.entries = [];
+
+    for (let i = 0; i < OBJECT_PREVIEW_MAX_ITEMS &&
+                    i < rawObj.length; i++) {
+      let prop = rawObj[i];
+      let value = rawObj.getPropertyValue(prop);
+      entries.push([prop, hooks.createValueGrip(value)]);
+    }
+
+    return true;
+  },
+
+  function DOMNode({obj, hooks}, grip, rawObj) {
+    if (isWorker || obj.class == "Object" || !rawObj ||
+        !(rawObj instanceof Ci.nsIDOMNode)) {
+      return false;
+    }
+
+    let preview = grip.preview = {
+      kind: "DOMNode",
+      nodeType: rawObj.nodeType,
+      nodeName: rawObj.nodeName,
+    };
+
+    if (rawObj instanceof Ci.nsIDOMDocument && rawObj.location) {
+      preview.location = hooks.createValueGrip(rawObj.location.href);
+    } else if (rawObj instanceof Ci.nsIDOMDocumentFragment) {
+      preview.childNodesLength = rawObj.childNodes.length;
+
+      if (hooks.getGripDepth() < 2) {
+        preview.childNodes = [];
+        for (let node of rawObj.childNodes) {
+          let actor = hooks.createValueGrip(obj.makeDebuggeeValue(node));
+          preview.childNodes.push(actor);
+          if (preview.childNodes.length == OBJECT_PREVIEW_MAX_ITEMS) {
+            break;
+          }
+        }
+      }
+    } else if (rawObj instanceof Ci.nsIDOMElement) {
+      // Add preview for DOM element attributes.
+      if (rawObj instanceof Ci.nsIDOMHTMLElement) {
+        preview.nodeName = preview.nodeName.toLowerCase();
+      }
+
+      let i = 0;
+      preview.attributes = {};
+      preview.attributesLength = rawObj.attributes.length;
+      for (let attr of rawObj.attributes) {
+        preview.attributes[attr.nodeName] = hooks.createValueGrip(attr.value);
+      }
+    } else if (rawObj instanceof Ci.nsIDOMAttr) {
+      preview.value = hooks.createValueGrip(rawObj.value);
+    } else if (rawObj instanceof Ci.nsIDOMText ||
+               rawObj instanceof Ci.nsIDOMComment) {
+      preview.textContent = hooks.createValueGrip(rawObj.textContent);
+    }
+
+    return true;
+  },
+
+  function DOMEvent({obj, hooks}, grip, rawObj) {
+    if (isWorker || !rawObj || !(rawObj instanceof Ci.nsIDOMEvent)) {
+      return false;
+    }
+
+    let preview = grip.preview = {
+      kind: "DOMEvent",
+      type: rawObj.type,
+      properties: Object.create(null),
+    };
+
+    if (hooks.getGripDepth() < 2) {
+      let target = obj.makeDebuggeeValue(rawObj.target);
+      preview.target = hooks.createValueGrip(target);
+    }
+
+    let props = [];
+    if (rawObj instanceof Ci.nsIDOMMouseEvent) {
+      props.push("buttons", "clientX", "clientY", "layerX", "layerY");
+    } else if (rawObj instanceof Ci.nsIDOMKeyEvent) {
+      let modifiers = [];
+      if (rawObj.altKey) {
+        modifiers.push("Alt");
+      }
+      if (rawObj.ctrlKey) {
+        modifiers.push("Control");
+      }
+      if (rawObj.metaKey) {
+        modifiers.push("Meta");
+      }
+      if (rawObj.shiftKey) {
+        modifiers.push("Shift");
+      }
+      preview.eventKind = "key";
+      preview.modifiers = modifiers;
+
+      props.push("key", "charCode", "keyCode");
+    } else if (rawObj instanceof Ci.nsIDOMTransitionEvent) {
+      props.push("propertyName", "pseudoElement");
+    } else if (rawObj instanceof Ci.nsIDOMAnimationEvent) {
+      props.push("animationName", "pseudoElement");
+    } else if (rawObj instanceof Ci.nsIDOMClipboardEvent) {
+      props.push("clipboardData");
+    }
+
+    // Add event-specific properties.
+    for (let prop of props) {
+      let value = rawObj[prop];
+      if (value && (typeof value == "object" || typeof value == "function")) {
+        // Skip properties pointing to objects.
+        if (hooks.getGripDepth() > 1) {
+          continue;
+        }
+        value = obj.makeDebuggeeValue(value);
+      }
+      preview.properties[prop] = hooks.createValueGrip(value);
+    }
+
+    // Add any properties we find on the event object.
+    if (!props.length) {
+      let i = 0;
+      for (let prop in rawObj) {
+        let value = rawObj[prop];
+        if (prop == "target" || prop == "type" || value === null ||
+            typeof value == "function") {
+          continue;
+        }
+        if (value && typeof value == "object") {
+          if (hooks.getGripDepth() > 1) {
+            continue;
+          }
+          value = obj.makeDebuggeeValue(value);
+        }
+        preview.properties[prop] = hooks.createValueGrip(value);
+        if (++i == OBJECT_PREVIEW_MAX_ITEMS) {
+          break;
+        }
+      }
+    }
+
+    return true;
+  },
+
+  function DOMException({obj, hooks}, grip, rawObj) {
+    if (isWorker || !rawObj || !(rawObj instanceof Ci.nsIDOMDOMException)) {
+      return false;
+    }
+
+    grip.preview = {
+      kind: "DOMException",
+      name: hooks.createValueGrip(rawObj.name),
+      message: hooks.createValueGrip(rawObj.message),
+      code: hooks.createValueGrip(rawObj.code),
+      result: hooks.createValueGrip(rawObj.result),
+      filename: hooks.createValueGrip(rawObj.filename),
+      lineNumber: hooks.createValueGrip(rawObj.lineNumber),
+      columnNumber: hooks.createValueGrip(rawObj.columnNumber),
+    };
+
+    return true;
+  },
+
+  function PseudoArray({obj, hooks}, grip, rawObj) {
+    let length;
+
+    let keys = obj.getOwnPropertyNames();
+    if (keys.length == 0) {
+      return false;
+    }
+
+    // If no item is going to be displayed in preview, better display as sparse object.
+    // The first key should contain the smallest integer index (if any).
+    if(keys[0] >= OBJECT_PREVIEW_MAX_ITEMS) {
+      return false;
+    }
+
+    // Pseudo-arrays should only have array indices and, optionally, a "length" property.
+    // Since integer indices are sorted first, check if the last property is "length".
+    if(keys[keys.length-1] === "length") {
+      keys.pop();
+      length = DevToolsUtils.getProperty(obj, "length");
+    } else {
+      // Otherwise, let length be the (presumably) greatest array index plus 1.
+      length = +keys[keys.length-1] + 1;
+    }
+    // Check if length is a valid array length, i.e. is a Uint32 number.
+    if(typeof length !== "number" || length >>> 0 !== length) {
+      return false;
+    }
+
+    // Ensure all keys are increasing array indices smaller than length. The order is not
+    // guaranteed for exotic objects but, in most cases, big array indices and properties
+    // which are not integer indices should be at the end. Then, iterating backwards
+    // allows us to return earlier when the object is not completely a pseudo-array.
+    let prev = length;
+    for(let i = keys.length - 1; i >= 0; --i) {
+      let key = keys[i];
+      let numKey = key >>> 0; // ToUint32(key)
+      if (numKey + '' !== key || numKey >= prev) {
+        return false;
+      }
+      prev = numKey;
+    }
+
+    grip.preview = {
+      kind: "ArrayLike",
+      length: length,
+    };
+
+    // Avoid recursive object grips.
+    if (hooks.getGripDepth() > 1) {
+      return true;
+    }
+
+    let items = grip.preview.items = [];
+    let numItems = Math.min(OBJECT_PREVIEW_MAX_ITEMS, length);
+
+    for (let i = 0; i < numItems; ++i) {
+      let desc = obj.getOwnPropertyDescriptor(i);
+      if (desc && 'value' in desc) {
+        items.push(hooks.createValueGrip(desc.value));
+      } else {
+        items.push(null);
+      }
+    }
+
+    return true;
+  },
+
+  function Object(objectActor, grip, rawObj) {
+    return GenericObject(objectActor, grip, rawObj, /* specialStringBehavior = */ false);
+  },
+];
+
+/**
+ * Get thisDebugger.Object referent's `promiseState`.
+ *
+ * @returns Object
+ *          An object of one of the following forms:
+ *          - { state: "pending" }
+ *          - { state: "fulfilled", value }
+ *          - { state: "rejected", reason }
+ */
+function getPromiseState(obj) {
+  if (obj.class != "Promise") {
+    throw new Error(
+      "Can't call `getPromiseState` on `Debugger.Object`s that don't " +
+      "refer to Promise objects.");
+  }
+
+  let state = { state: obj.promiseState };
+  if (state.state === "fulfilled") {
+    state.value = obj.promiseValue;
+  } else if (state.state === "rejected") {
+    state.reason = obj.promiseReason;
+  }
+  return state;
+}
+
+/**
+ * Determine if a given value is non-primitive.
+ *
+ * @param Any value
+ *        The value to test.
+ * @return Boolean
+ *         Whether the value is non-primitive.
+ */
+function isObject(value) {
+  const type = typeof value;
+  return type == "object" ? value !== null : type == "function";
+}
+
+/**
+ * Create a function that can safely stringify Debugger.Objects of a given
+ * builtin type.
+ *
+ * @param Function ctor
+ *        The builtin class constructor.
+ * @return Function
+ *         The stringifier for the class.
+ */
+function createBuiltinStringifier(ctor) {
+  return obj => ctor.prototype.toString.call(obj.unsafeDereference());
+}
+
+/**
+ * Stringify a Debugger.Object-wrapped Error instance.
+ *
+ * @param Debugger.Object obj
+ *        The object to stringify.
+ * @return String
+ *         The stringification of the object.
+ */
+function errorStringify(obj) {
+  let name = DevToolsUtils.getProperty(obj, "name");
+  if (name === "" || name === undefined) {
+    name = obj.class;
+  } else if (isObject(name)) {
+    name = stringify(name);
+  }
+
+  let message = DevToolsUtils.getProperty(obj, "message");
+  if (isObject(message)) {
+    message = stringify(message);
+  }
+
+  if (message === "" || message === undefined) {
+    return name;
+  }
+  return name + ": " + message;
+}
+
+/**
+ * Stringify a Debugger.Object based on its class.
+ *
+ * @param Debugger.Object obj
+ *        The object to stringify.
+ * @return String
+ *         The stringification for the object.
+ */
+function stringify(obj) {
+  if (obj.class == "DeadObject") {
+    const error = new Error("Dead object encountered.");
+    DevToolsUtils.reportException("stringify", error);
+    return "<dead object>";
+  }
+
+  const stringifier = stringifiers[obj.class] || stringifiers.Object;
+
+  try {
+    return stringifier(obj);
+  } catch (e) {
+    DevToolsUtils.reportException("stringify", e);
+    return "<failed to stringify object>";
+  }
+}
+
+// Used to prevent infinite recursion when an array is found inside itself.
+var seen = null;
+
+var stringifiers = {
+  Error: errorStringify,
+  EvalError: errorStringify,
+  RangeError: errorStringify,
+  ReferenceError: errorStringify,
+  SyntaxError: errorStringify,
+  TypeError: errorStringify,
+  URIError: errorStringify,
+  Boolean: createBuiltinStringifier(Boolean),
+  Function: createBuiltinStringifier(Function),
+  Number: createBuiltinStringifier(Number),
+  RegExp: createBuiltinStringifier(RegExp),
+  String: createBuiltinStringifier(String),
+  Object: obj => "[object " + obj.class + "]",
+  Array: obj => {
+    // If we're at the top level then we need to create the Set for tracking
+    // previously stringified arrays.
+    const topLevel = !seen;
+    if (topLevel) {
+      seen = new Set();
+    } else if (seen.has(obj)) {
+      return "";
+    }
+
+    seen.add(obj);
+
+    const len = DevToolsUtils.getProperty(obj, "length");
+    let string = "";
+
+    // The following check is only required because the debuggee could possibly
+    // be a Proxy and return any value. For normal objects, array.length is
+    // always a non-negative integer.
+    if (typeof len == "number" && len > 0) {
+      for (let i = 0; i < len; i++) {
+        const desc = obj.getOwnPropertyDescriptor(i);
+        if (desc) {
+          const { value } = desc;
+          if (value != null) {
+            string += isObject(value) ? stringify(value) : value;
+          }
+        }
+
+        if (i < len - 1) {
+          string += ",";
+        }
+      }
+    }
+
+    if (topLevel) {
+      seen = null;
+    }
+
+    return string;
+  },
+  DOMException: obj => {
+    const message = DevToolsUtils.getProperty(obj, "message") || "<no message>";
+    const result = (+DevToolsUtils.getProperty(obj, "result")).toString(16);
+    const code = DevToolsUtils.getProperty(obj, "code");
+    const name = DevToolsUtils.getProperty(obj, "name") || "<unknown>";
+
+    return '[Exception... "' + message + '" ' +
+           'code: "' + code + '" ' +
+           'nsresult: "0x' + result + " (" + name + ')"]';
+  },
+  Promise: obj => {
+    const { state, value, reason } = getPromiseState(obj);
+    let statePreview = state;
+    if (state != "pending") {
+      const settledValue = state === "fulfilled" ? value : reason;
+      statePreview += ": " + (typeof settledValue === "object" && settledValue !== null
+                                ? stringify(settledValue)
+                                : settledValue);
+    }
+    return "Promise (" + statePreview + ")";
+  },
+};
+
+/**
+ * Make a debuggee value for the given object, if needed. Primitive values
+ * are left the same.
+ *
+ * Use case: you have a raw JS object (after unsafe dereference) and you want to
+ * send it to the client. In that case you need to use an ObjectActor which
+ * requires a debuggee value. The Debugger.Object.prototype.makeDebuggeeValue()
+ * method works only for JS objects and functions.
+ *
+ * @param Debugger.Object obj
+ * @param any value
+ * @return object
+ */
+function makeDebuggeeValueIfNeeded(obj, value) {
+  if (value && (typeof value == "object" || typeof value == "function")) {
+    return obj.makeDebuggeeValue(value);
+  }
+  return value;
+}
+
+/**
+ * Creates an actor for the specied "very long" string. "Very long" is specified
+ * at the server's discretion.
+ *
+ * @param string String
+ *        The string.
+ */
+function LongStringActor(string) {
+  this.string = string;
+  this.stringLength = string.length;
+}
+
+LongStringActor.prototype = {
+  actorPrefix: "longString",
+
+  disconnect: function () {
+    // Because longStringActors is not a weak map, we won't automatically leave
+    // it so we need to manually leave on disconnect so that we don't leak
+    // memory.
+    this._releaseActor();
+  },
+
+  /**
+   * Returns a grip for this actor for returning in a protocol message.
+   */
+  grip: function () {
+    return {
+      "type": "longString",
+      "initial": this.string.substring(
+        0, DebuggerServer.LONG_STRING_INITIAL_LENGTH),
+      "length": this.stringLength,
+      "actor": this.actorID
+    };
+  },
+
+  /**
+   * Handle a request to extract part of this actor's string.
+   *
+   * @param request object
+   *        The protocol request object.
+   */
+  onSubstring: function (request) {
+    return {
+      "from": this.actorID,
+      "substring": this.string.substring(request.start, request.end)
+    };
+  },
+
+  /**
+   * Handle a request to release this LongStringActor instance.
+   */
+  onRelease: function () {
+    // TODO: also check if registeredPool === threadActor.threadLifetimePool
+    // when the web console moves aray from manually releasing pause-scoped
+    // actors.
+    this._releaseActor();
+    this.registeredPool.removeActor(this);
+    return {};
+  },
+
+  _releaseActor: function () {
+    if (this.registeredPool && this.registeredPool.longStringActors) {
+      delete this.registeredPool.longStringActors[this.string];
+    }
+  }
+};
+
+LongStringActor.prototype.requestTypes = {
+  "substring": LongStringActor.prototype.onSubstring,
+  "release": LongStringActor.prototype.onRelease
+};
+
+/**
+ * Create a grip for the given debuggee value.  If the value is an
+ * object, will create an actor with the given lifetime.
+ */
+function createValueGrip(value, pool, makeObjectGrip) {
+  switch (typeof value) {
+    case "boolean":
+      return value;
+
+    case "string":
+      if (stringIsLong(value)) {
+        return longStringGrip(value, pool);
+      }
+      return value;
+
+    case "number":
+      if (value === Infinity) {
+        return { type: "Infinity" };
+      } else if (value === -Infinity) {
+        return { type: "-Infinity" };
+      } else if (Number.isNaN(value)) {
+        return { type: "NaN" };
+      } else if (!value && 1 / value === -Infinity) {
+        return { type: "-0" };
+      }
+      return value;
+
+    case "undefined":
+      return { type: "undefined" };
+
+    case "object":
+      if (value === null) {
+        return { type: "null" };
+      }
+      else if (value.optimizedOut ||
+             value.uninitialized ||
+             value.missingArguments) {
+        // The slot is optimized out, an uninitialized binding, or
+        // arguments on a dead scope
+        return {
+          type: "null",
+          optimizedOut: value.optimizedOut,
+          uninitialized: value.uninitialized,
+          missingArguments: value.missingArguments
+        };
+      }
+      return makeObjectGrip(value, pool);
+
+    case "symbol":
+      let form = {
+        type: "symbol"
+      };
+      let name = getSymbolName(value);
+      if (name !== undefined) {
+        form.name = createValueGrip(name, pool, makeObjectGrip);
+      }
+      return form;
+
+    default:
+      assert(false, "Failed to provide a grip for: " + value);
+      return null;
+  }
+}
+
+const symbolProtoToString = Symbol.prototype.toString;
+
+function getSymbolName(symbol) {
+  const name = symbolProtoToString.call(symbol).slice("Symbol(".length, -1);
+  return name || undefined;
+}
+
+/**
+ * Returns true if the string is long enough to use a LongStringActor instead
+ * of passing the value directly over the protocol.
+ *
+ * @param str String
+ *        The string we are checking the length of.
+ */
+function stringIsLong(str) {
+  return str.length >= DebuggerServer.LONG_STRING_LENGTH;
+}
+
+/**
+ * Create a grip for the given string.
+ *
+ * @param str String
+ *        The string we are creating a grip for.
+ * @param pool ActorPool
+ *        The actor pool where the new actor will be added.
+ */
+function longStringGrip(str, pool) {
+  if (!pool.longStringActors) {
+    pool.longStringActors = {};
+  }
+
+  if (pool.longStringActors.hasOwnProperty(str)) {
+    return pool.longStringActors[str].grip();
+  }
+
+  let actor = new LongStringActor(str);
+  pool.addActor(actor);
+  pool.longStringActors[str] = actor;
+  return actor.grip();
+}
+
+exports.ObjectActor = ObjectActor;
+exports.PropertyIteratorActor = PropertyIteratorActor;
+exports.LongStringActor = LongStringActor;
+exports.createValueGrip = createValueGrip;
+exports.stringIsLong = stringIsLong;
+exports.longStringGrip = longStringGrip;
diff --git a/devtools/server/actors/performance-entries.js b/devtools/server/actors/performance-entries.js
new file mode 100644
index 000000000..89434324a
--- /dev/null
+++ b/devtools/server/actors/performance-entries.js
@@ -0,0 +1,65 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * The performanceEntries actor emits events corresponding to performance
+ * entries. It receives `performanceentry` events containing the performance
+ * entry details and emits an event containing the name, type, origin, and
+ * epoch of the performance entry.
+ */
+
+const { Actor, ActorClassWithSpec } = require("devtools/shared/protocol");
+const performanceSpec = require("devtools/shared/specs/performance-entries");
+const events = require("sdk/event/core");
+
+var PerformanceEntriesActor = ActorClassWithSpec(performanceSpec, {
+  listenerAdded: false,
+
+  initialize: function (conn, tabActor) {
+    Actor.prototype.initialize.call(this, conn);
+    this.window = tabActor.window;
+  },
+
+  /**
+   * Start tracking the user timings.
+   */
+  start: function () {
+    if (!this.listenerAdded) {
+      this.onPerformanceEntry = this.onPerformanceEntry.bind(this);
+      this.window.addEventListener("performanceentry", this.onPerformanceEntry, true);
+      this.listenerAdded = true;
+    }
+  },
+
+  /**
+   * Stop tracking the user timings.
+   */
+  stop: function () {
+    if (this.listenerAdded) {
+      this.window.removeEventListener("performanceentry", this.onPerformanceEntry, true);
+      this.listenerAdded = false;
+    }
+  },
+
+  disconnect: function () {
+    this.destroy();
+  },
+
+  destroy: function () {
+    this.stop();
+    Actor.prototype.destroy.call(this);
+  },
+
+  onPerformanceEntry: function (e) {
+    let emitDetail = {
+      type: e.entryType,
+      name: e.name,
+      origin: e.origin,
+      epoch: e.epoch
+    };
+    events.emit(this, "entry", emitDetail);
+  }
+});
+
+exports.PerformanceEntriesActor = PerformanceEntriesActor;
diff --git a/devtools/server/actors/performance-recording.js b/devtools/server/actors/performance-recording.js
new file mode 100644
index 000000000..ef5907495
--- /dev/null
+++ b/devtools/server/actors/performance-recording.js
@@ -0,0 +1,148 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cu } = require("chrome");
+const { Actor, ActorClassWithSpec } = require("devtools/shared/protocol");
+const { performanceRecordingSpec } = require("devtools/shared/specs/performance-recording");
+
+loader.lazyRequireGetter(this, "merge", "sdk/util/object", true);
+loader.lazyRequireGetter(this, "RecordingUtils",
+  "devtools/shared/performance/recording-utils");
+loader.lazyRequireGetter(this, "PerformanceRecordingCommon",
+  "devtools/shared/performance/recording-common", true);
+
+/**
+ * This actor wraps the Performance module at devtools/shared/shared/performance.js
+ * and provides RDP definitions.
+ *
+ * @see devtools/shared/shared/performance.js for documentation.
+ */
+const PerformanceRecordingActor = ActorClassWithSpec(performanceRecordingSpec, merge({
+  form: function (detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    let form = {
+      actor: this.actorID,  // actorID is set when this is added to a pool
+      configuration: this._configuration,
+      startingBufferStatus: this._startingBufferStatus,
+      console: this._console,
+      label: this._label,
+      startTime: this._startTime,
+      localStartTime: this._localStartTime,
+      recording: this._recording,
+      completed: this._completed,
+      duration: this._duration,
+    };
+
+    // Only send profiler data once it exists and it has
+    // not yet been sent
+    if (this._profile && !this._sentFinalizedData) {
+      form.finalizedData = true;
+      form.profile = this.getProfile();
+      form.systemHost = this.getHostSystemInfo();
+      form.systemClient = this.getClientSystemInfo();
+      this._sentFinalizedData = true;
+    }
+
+    return form;
+  },
+
+  /**
+   * @param {object} conn
+   * @param {object} options
+   *        A hash of features that this recording is utilizing.
+   * @param {object} meta
+   *        A hash of temporary metadata for a recording that is recording
+   *        (as opposed to an imported recording).
+   */
+  initialize: function (conn, options, meta) {
+    Actor.prototype.initialize.call(this, conn);
+    this._configuration = {
+      withMarkers: options.withMarkers || false,
+      withTicks: options.withTicks || false,
+      withMemory: options.withMemory || false,
+      withAllocations: options.withAllocations || false,
+      allocationsSampleProbability: options.allocationsSampleProbability || 0,
+      allocationsMaxLogLength: options.allocationsMaxLogLength || 0,
+      bufferSize: options.bufferSize || 0,
+      sampleFrequency: options.sampleFrequency || 1
+    };
+
+    this._console = !!options.console;
+    this._label = options.label || "";
+
+    if (meta) {
+      // Store the start time roughly with Date.now() so when we
+      // are checking the duration during a recording, we can get close
+      // to the approximate duration to render elements without
+      // making a real request
+      this._localStartTime = Date.now();
+
+      this._startTime = meta.startTime;
+      this._startingBufferStatus = {
+        position: meta.position,
+        totalSize: meta.totalSize,
+        generation: meta.generation
+      };
+
+      this._recording = true;
+      this._markers = [];
+      this._frames = [];
+      this._memory = [];
+      this._ticks = [];
+      this._allocations = { sites: [], timestamps: [], frames: [], sizes: [] };
+
+      this._systemHost = meta.systemHost || {};
+      this._systemClient = meta.systemClient || {};
+    }
+  },
+
+  destroy: function () {
+    Actor.prototype.destroy.call(this);
+  },
+
+  /**
+   * Internal utility called by the PerformanceActor and PerformanceFront on state changes
+   * to update the internal state of the PerformanceRecording.
+   *
+   * @param {string} state
+   * @param {object} extraData
+   */
+  _setState: function (state, extraData) {
+    switch (state) {
+      case "recording-started": {
+        this._recording = true;
+        break;
+      }
+      case "recording-stopping": {
+        this._recording = false;
+        break;
+      }
+      case "recording-stopped": {
+        this._profile = extraData.profile;
+        this._duration = extraData.duration;
+
+        // We filter out all samples that fall out of current profile's range
+        // since the profiler is continuously running. Because of this, sample
+        // times are not guaranteed to have a zero epoch, so offset the
+        // timestamps.
+        RecordingUtils.offsetSampleTimes(this._profile, this._startTime);
+
+        // Markers need to be sorted ascending by time, to be properly displayed
+        // in a waterfall view.
+        this._markers = this._markers.sort((a, b) => (a.start > b.start));
+
+        this._completed = true;
+        break;
+      }
+    }
+  },
+
+}, PerformanceRecordingCommon));
+
+exports.PerformanceRecordingActor = PerformanceRecordingActor;
diff --git a/devtools/server/actors/performance.js b/devtools/server/actors/performance.js
new file mode 100644
index 000000000..8b294a4de
--- /dev/null
+++ b/devtools/server/actors/performance.js
@@ -0,0 +1,116 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cu } = require("chrome");
+const { Task } = require("devtools/shared/task");
+const { Actor, ActorClassWithSpec } = require("devtools/shared/protocol");
+const { actorBridgeWithSpec } = require("devtools/server/actors/common");
+const { performanceSpec } = require("devtools/shared/specs/performance");
+
+loader.lazyRequireGetter(this, "events", "sdk/event/core");
+loader.lazyRequireGetter(this, "extend", "sdk/util/object", true);
+
+loader.lazyRequireGetter(this, "PerformanceRecorder",
+  "devtools/server/performance/recorder", true);
+loader.lazyRequireGetter(this, "normalizePerformanceFeatures",
+  "devtools/shared/performance/recording-utils", true);
+
+const PIPE_TO_FRONT_EVENTS = new Set([
+  "recording-started", "recording-stopping", "recording-stopped",
+  "profiler-status", "timeline-data", "console-profile-start"
+]);
+
+const RECORDING_STATE_CHANGE_EVENTS = new Set([
+  "recording-started", "recording-stopping", "recording-stopped"
+]);
+
+/**
+ * This actor wraps the Performance module at devtools/shared/shared/performance.js
+ * and provides RDP definitions.
+ *
+ * @see devtools/shared/shared/performance.js for documentation.
+ */
+var PerformanceActor = ActorClassWithSpec(performanceSpec, {
+  traits: {
+    features: {
+      withMarkers: true,
+      withTicks: true,
+      withMemory: true,
+      withFrames: true,
+      withGCEvents: true,
+      withDocLoadingEvents: true,
+      withAllocations: true,
+    },
+  },
+
+  initialize: function (conn, tabActor) {
+    Actor.prototype.initialize.call(this, conn);
+    this._onRecorderEvent = this._onRecorderEvent.bind(this);
+    this.bridge = new PerformanceRecorder(conn, tabActor);
+    events.on(this.bridge, "*", this._onRecorderEvent);
+  },
+
+  /**
+   * `disconnect` method required to call destroy, since this
+   * actor is not managed by a parent actor.
+   */
+  disconnect: function () {
+    this.destroy();
+  },
+
+  destroy: function () {
+    events.off(this.bridge, "*", this._onRecorderEvent);
+    this.bridge.destroy();
+    Actor.prototype.destroy.call(this);
+  },
+
+  connect: function (config) {
+    this.bridge.connect({ systemClient: config.systemClient });
+    return { traits: this.traits };
+  },
+
+  canCurrentlyRecord: function () {
+    return this.bridge.canCurrentlyRecord();
+  },
+
+  startRecording: Task.async(function* (options = {}) {
+    if (!this.bridge.canCurrentlyRecord().success) {
+      return null;
+    }
+
+    let normalizedOptions = normalizePerformanceFeatures(options, this.traits.features);
+    let recording = yield this.bridge.startRecording(normalizedOptions);
+    this.manage(recording);
+
+    return recording;
+  }),
+
+  stopRecording: actorBridgeWithSpec("stopRecording"),
+  isRecording: actorBridgeWithSpec("isRecording"),
+  getRecordings: actorBridgeWithSpec("getRecordings"),
+  getConfiguration: actorBridgeWithSpec("getConfiguration"),
+  setProfilerStatusInterval: actorBridgeWithSpec("setProfilerStatusInterval"),
+
+  /**
+   * Filter which events get piped to the front.
+   */
+  _onRecorderEvent: function (eventName, ...data) {
+    // If this is a recording state change, call
+    // a method on the related PerformanceRecordingActor so it can
+    // update its internal state.
+    if (RECORDING_STATE_CHANGE_EVENTS.has(eventName)) {
+      let recording = data[0];
+      let extraData = data[1];
+      recording._setState(eventName, extraData);
+    }
+
+    if (PIPE_TO_FRONT_EVENTS.has(eventName)) {
+      events.emit(this, eventName, ...data);
+    }
+  },
+});
+
+exports.PerformanceActor = PerformanceActor;
diff --git a/devtools/server/actors/preference.js b/devtools/server/actors/preference.js
new file mode 100644
index 000000000..8d4140155
--- /dev/null
+++ b/devtools/server/actors/preference.js
@@ -0,0 +1,81 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const {Cc, Ci, Cu, CC} = require("chrome");
+const protocol = require("devtools/shared/protocol");
+const {Arg, method, RetVal} = protocol;
+const Services = require("Services");
+const {preferenceSpec} = require("devtools/shared/specs/preference");
+
+exports.register = function (handle) {
+  handle.addGlobalActor(PreferenceActor, "preferenceActor");
+};
+
+exports.unregister = function (handle) {
+};
+
+var PreferenceActor = exports.PreferenceActor = protocol.ActorClassWithSpec(preferenceSpec, {
+  typeName: "preference",
+
+  getBoolPref: function (name) {
+    return Services.prefs.getBoolPref(name);
+  },
+
+  getCharPref: function (name) {
+    return Services.prefs.getCharPref(name);
+  },
+
+  getIntPref: function (name) {
+    return Services.prefs.getIntPref(name);
+  },
+
+  getAllPrefs: function () {
+    let prefs = {};
+    Services.prefs.getChildList("").forEach(function (name, index) {
+      // append all key/value pairs into a huge json object.
+      try {
+        let value;
+        switch (Services.prefs.getPrefType(name)) {
+          case Ci.nsIPrefBranch.PREF_STRING:
+            value = Services.prefs.getCharPref(name);
+            break;
+          case Ci.nsIPrefBranch.PREF_INT:
+            value = Services.prefs.getIntPref(name);
+            break;
+          case Ci.nsIPrefBranch.PREF_BOOL:
+            value = Services.prefs.getBoolPref(name);
+            break;
+          default:
+        }
+        prefs[name] = {
+          value: value,
+          hasUserValue: Services.prefs.prefHasUserValue(name)
+        };
+      } catch (e) {
+        // pref exists but has no user or default value
+      }
+    });
+    return prefs;
+  },
+
+  setBoolPref: function (name, value) {
+    Services.prefs.setBoolPref(name, value);
+    Services.prefs.savePrefFile(null);
+  },
+
+  setCharPref: function (name, value) {
+    Services.prefs.setCharPref(name, value);
+    Services.prefs.savePrefFile(null);
+  },
+
+  setIntPref: function (name, value) {
+    Services.prefs.setIntPref(name, value);
+    Services.prefs.savePrefFile(null);
+  },
+
+  clearUserPref: function (name) {
+    Services.prefs.clearUserPref(name);
+    Services.prefs.savePrefFile(null);
+  },
+});
diff --git a/devtools/server/actors/pretty-print-worker.js b/devtools/server/actors/pretty-print-worker.js
new file mode 100644
index 000000000..5fc6b6959
--- /dev/null
+++ b/devtools/server/actors/pretty-print-worker.js
@@ -0,0 +1,50 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This file is meant to be loaded as a ChromeWorker. It accepts messages which
+ * have data of the form:
+ *
+ *     { id, url, indent, source }
+ *
+ * Where `id` is a unique ID to identify this request, `url` is the url of the
+ * source being pretty printed, `indent` is the number of spaces to indent the
+ * code by, and `source` is the source text.
+ *
+ * On success, the worker responds with a message of the form:
+ *
+ *     { id, code, mappings }
+ *
+ * Where `id` is the same unique ID from the request, `code` is the pretty
+ * printed source text, and `mappings` is an array or source mappings from the
+ * pretty printed code back to the ugly source text.
+ *
+ * In the case of an error, the worker responds with a message of the form:
+ *
+ *     { id, error }
+ */
+
+importScripts("resource://devtools/shared/worker/helper.js");
+importScripts("resource://devtools/shared/acorn/acorn.js");
+importScripts("resource://devtools/shared/sourcemap/source-map.js");
+importScripts("resource://devtools/shared/pretty-fast/pretty-fast.js");
+
+workerHelper.createTask(self, "pretty-print", ({ url, indent, source }) => {
+  try {
+    const prettified = prettyFast(source, {
+      url: url,
+      indent: " ".repeat(indent)
+    });
+
+    return {
+      code: prettified.code,
+      mappings: prettified.map._mappings
+    };
+  }
+  catch (e) {
+    return new Error(e.message + "\n" + e.stack);
+  }
+});
diff --git a/devtools/server/actors/process.js b/devtools/server/actors/process.js
new file mode 100644
index 000000000..ff1c4313f
--- /dev/null
+++ b/devtools/server/actors/process.js
@@ -0,0 +1,83 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { Cc, Ci } = require("chrome");
+
+loader.lazyGetter(this, "ppmm", () => {
+  return Cc["@mozilla.org/parentprocessmessagemanager;1"].getService(Ci.nsIMessageBroadcaster);
+});
+
+function ProcessActorList() {
+  this._actors = new Map();
+  this._onListChanged = null;
+  this._mustNotify = false;
+
+  this._onMessage = this._onMessage.bind(this);
+  this._processScript = "data:text/javascript,sendAsyncMessage('debug:new-process');";
+}
+
+ProcessActorList.prototype = {
+  getList: function () {
+    let processes = [];
+    for (let i = 0; i < ppmm.childCount; i++) {
+      processes.push({
+        id: i, // XXX: may not be a perfect id, but process message manager doesn't expose anything...
+        parent: i == 0, // XXX Weak, but appear to be stable
+        tabCount: undefined, // TODO: exposes process message manager on frameloaders in order to compute this
+      });
+    }
+    this._mustNotify = true;
+    this._checkListening();
+
+    return processes;
+  },
+
+  get onListChanged() {
+    return this._onListChanged;
+  },
+
+  set onListChanged(onListChanged) {
+    if (typeof onListChanged !== "function" && onListChanged !== null) {
+      throw new Error("onListChanged must be either a function or null.");
+    }
+    if (onListChanged === this._onListChanged) {
+      return;
+    }
+
+    this._onListChanged = onListChanged;
+    this._checkListening();
+  },
+
+  _checkListening: function () {
+    if (this._onListChanged !== null && this._mustNotify) {
+      this._knownProcesses = [];
+      for (let i = 0; i < ppmm.childCount; i++) {
+        this._knownProcesses.push(ppmm.getChildAt(i));
+      }
+      ppmm.addMessageListener("debug:new-process", this._onMessage);
+      ppmm.loadProcessScript(this._processScript, true);
+    } else {
+      ppmm.removeMessageListener("debug:new-process", this._onMessage);
+      ppmm.removeDelayedProcessScript(this._processScript);
+    }
+  },
+
+  _notifyListChanged: function () {
+    if (this._mustNotify) {
+      this._onListChanged();
+      this._mustNotify = false;
+    }
+  },
+
+  _onMessage: function ({ target }) {
+    if (this._knownProcesses.includes(target)) {
+      return;
+    }
+    this._notifyListChanged();
+  },
+};
+
+exports.ProcessActorList = ProcessActorList;
diff --git a/devtools/server/actors/profiler.js b/devtools/server/actors/profiler.js
new file mode 100644
index 000000000..c4b594408
--- /dev/null
+++ b/devtools/server/actors/profiler.js
@@ -0,0 +1,60 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const { Actor, ActorClassWithSpec } = require("devtools/shared/protocol");
+const { Profiler } = require("devtools/server/performance/profiler");
+const { actorBridgeWithSpec } = require("devtools/server/actors/common");
+const { profilerSpec } = require("devtools/shared/specs/profiler");
+
+loader.lazyRequireGetter(this, "events", "sdk/event/core");
+
+/**
+ * This actor wraps the Profiler module at devtools/server/performance/profiler.js
+ * and provides RDP definitions.
+ *
+ * @see devtools/server/performance/profiler.js for documentation.
+ */
+var ProfilerActor = exports.ProfilerActor = ActorClassWithSpec(profilerSpec, {
+  initialize: function (conn) {
+    Actor.prototype.initialize.call(this, conn);
+    this._onProfilerEvent = this._onProfilerEvent.bind(this);
+
+    this.bridge = new Profiler();
+    events.on(this.bridge, "*", this._onProfilerEvent);
+  },
+
+  /**
+   * `disconnect` method required to call destroy, since this
+   * actor is not managed by a parent actor.
+   */
+  disconnect: function () {
+    this.destroy();
+  },
+
+  destroy: function () {
+    events.off(this.bridge, "*", this._onProfilerEvent);
+    this.bridge.destroy();
+    Actor.prototype.destroy.call(this);
+  },
+
+  startProfiler: actorBridgeWithSpec("start"),
+  stopProfiler: actorBridgeWithSpec("stop"),
+  getProfile: actorBridgeWithSpec("getProfile"),
+  getFeatures: actorBridgeWithSpec("getFeatures"),
+  getBufferInfo: actorBridgeWithSpec("getBufferInfo"),
+  getStartOptions: actorBridgeWithSpec("getStartOptions"),
+  isActive: actorBridgeWithSpec("isActive"),
+  getSharedLibraryInformation: actorBridgeWithSpec("getSharedLibraryInformation"),
+  registerEventNotifications: actorBridgeWithSpec("registerEventNotifications"),
+  unregisterEventNotifications: actorBridgeWithSpec("unregisterEventNotifications"),
+  setProfilerStatusInterval: actorBridgeWithSpec("setProfilerStatusInterval"),
+
+  /**
+   * Pipe events from Profiler module to this actor.
+   */
+  _onProfilerEvent: function (eventName, ...data) {
+    events.emit(this, eventName, ...data);
+  },
+});
diff --git a/devtools/server/actors/promises.js b/devtools/server/actors/promises.js
new file mode 100644
index 000000000..a9a56219d
--- /dev/null
+++ b/devtools/server/actors/promises.js
@@ -0,0 +1,200 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const protocol = require("devtools/shared/protocol");
+const { promisesSpec } = require("devtools/shared/specs/promises");
+const { expectState, ActorPool } = require("devtools/server/actors/common");
+const { ObjectActor, createValueGrip } = require("devtools/server/actors/object");
+const DevToolsUtils = require("devtools/shared/DevToolsUtils");
+loader.lazyRequireGetter(this, "events", "sdk/event/core");
+
+/**
+ * The Promises Actor provides support for getting the list of live promises and
+ * observing changes to their settlement state.
+ */
+var PromisesActor = protocol.ActorClassWithSpec(promisesSpec, {
+  /**
+   * @param conn DebuggerServerConnection.
+   * @param parent TabActor|RootActor
+   */
+  initialize: function (conn, parent) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+
+    this.conn = conn;
+    this.parent = parent;
+    this.state = "detached";
+    this._dbg = null;
+    this._gripDepth = 0;
+    this._navigationLifetimePool = null;
+    this._newPromises = null;
+    this._promisesSettled = null;
+
+    this.objectGrip = this.objectGrip.bind(this);
+    this._makePromiseEventHandler = this._makePromiseEventHandler.bind(this);
+    this._onWindowReady = this._onWindowReady.bind(this);
+  },
+
+  destroy: function () {
+    protocol.Actor.prototype.destroy.call(this, this.conn);
+
+    if (this.state === "attached") {
+      this.detach();
+    }
+  },
+
+  get dbg() {
+    if (!this._dbg) {
+      this._dbg = this.parent.makeDebugger();
+    }
+    return this._dbg;
+  },
+
+  /**
+   * Attach to the PromisesActor.
+   */
+  attach: expectState("detached", function () {
+    this.dbg.addDebuggees();
+
+    this._navigationLifetimePool = this._createActorPool();
+    this.conn.addActorPool(this._navigationLifetimePool);
+
+    this._newPromises = [];
+    this._promisesSettled = [];
+
+    this.dbg.findScripts().forEach(s => {
+      this.parent.sources.createSourceActors(s.source);
+    });
+
+    this.dbg.onNewScript = s => {
+      this.parent.sources.createSourceActors(s.source);
+    };
+
+    events.on(this.parent, "window-ready", this._onWindowReady);
+
+    this.state = "attached";
+  }, "attaching to the PromisesActor"),
+
+  /**
+   * Detach from the PromisesActor upon Debugger closing.
+   */
+  detach: expectState("attached", function () {
+    this.dbg.removeAllDebuggees();
+    this.dbg.enabled = false;
+    this._dbg = null;
+    this._newPromises = null;
+    this._promisesSettled = null;
+
+    if (this._navigationLifetimePool) {
+      this.conn.removeActorPool(this._navigationLifetimePool);
+      this._navigationLifetimePool = null;
+    }
+
+    events.off(this.parent, "window-ready", this._onWindowReady);
+
+    this.state = "detached";
+  }),
+
+  _createActorPool: function () {
+    let pool = new ActorPool(this.conn);
+    pool.objectActors = new WeakMap();
+    return pool;
+  },
+
+  /**
+   * Create an ObjectActor for the given Promise object.
+   *
+   * @param object promise
+   *        The promise object
+   * @return object
+   *        An ObjectActor object that wraps the given Promise object
+   */
+  _createObjectActorForPromise: function (promise) {
+    if (this._navigationLifetimePool.objectActors.has(promise)) {
+      return this._navigationLifetimePool.objectActors.get(promise);
+    }
+
+    let actor = new ObjectActor(promise, {
+      getGripDepth: () => this._gripDepth,
+      incrementGripDepth: () => this._gripDepth++,
+      decrementGripDepth: () => this._gripDepth--,
+      createValueGrip: v =>
+        createValueGrip(v, this._navigationLifetimePool, this.objectGrip),
+      sources: () => this.parent.sources,
+      createEnvironmentActor: () => DevToolsUtils.reportException(
+        "PromisesActor", Error("createEnvironmentActor not yet implemented")),
+      getGlobalDebugObject: () => DevToolsUtils.reportException(
+        "PromisesActor", Error("getGlobalDebugObject not yet implemented")),
+    });
+
+    this._navigationLifetimePool.addActor(actor);
+    this._navigationLifetimePool.objectActors.set(promise, actor);
+
+    return actor;
+  },
+
+  /**
+   * Get a grip for the given Promise object.
+   *
+   * @param object value
+   *        The Promise object
+   * @return object
+   *        The grip for the given Promise object
+   */
+  objectGrip: function (value) {
+    return this._createObjectActorForPromise(value).grip();
+  },
+
+  /**
+   * Get a list of ObjectActors for all live Promise Objects.
+   */
+  listPromises: function () {
+    let promises = this.dbg.findObjects({ class: "Promise" });
+
+    this.dbg.onNewPromise = this._makePromiseEventHandler(this._newPromises,
+      "new-promises");
+    this.dbg.onPromiseSettled = this._makePromiseEventHandler(
+      this._promisesSettled, "promises-settled");
+
+    return promises.map(p => this._createObjectActorForPromise(p));
+  },
+
+  /**
+   * Creates an event handler for onNewPromise that will add the new
+   * Promise ObjectActor to the array and schedule it to be emitted as a
+   * batch for the provided event.
+   *
+   * @param array array
+   *        The list of Promise ObjectActors to emit
+   * @param string eventName
+   *        The event name
+   */
+  _makePromiseEventHandler: function (array, eventName) {
+    return promise => {
+      let actor = this._createObjectActorForPromise(promise);
+      let needsScheduling = array.length == 0;
+
+      array.push(actor);
+
+      if (needsScheduling) {
+        DevToolsUtils.executeSoon(() => {
+          events.emit(this, eventName, array.splice(0, array.length));
+        });
+      }
+    };
+  },
+
+  _onWindowReady: expectState("attached", function ({ isTopLevel }) {
+    if (!isTopLevel) {
+      return;
+    }
+
+    this._navigationLifetimePool.cleanup();
+    this.dbg.removeAllDebuggees();
+    this.dbg.addDebuggees();
+  })
+});
+
+exports.PromisesActor = PromisesActor;
diff --git a/devtools/server/actors/reflow.js b/devtools/server/actors/reflow.js
new file mode 100644
index 000000000..0ebe00207
--- /dev/null
+++ b/devtools/server/actors/reflow.js
@@ -0,0 +1,514 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * About the types of objects in this file:
+ *
+ * - ReflowActor: the actor class used for protocol purposes.
+ *   Mostly empty, just gets an instance of LayoutChangesObserver and forwards
+ *   its "reflows" events to clients.
+ *
+ * - LayoutChangesObserver: extends Observable and uses the ReflowObserver, to
+ *   track reflows on the page.
+ *   Used by the LayoutActor, but is also exported on the module, so can be used
+ *   by any other actor that needs it.
+ *
+ * - Observable: A utility parent class, meant at being extended by classes that
+ *   need a to observe something on the tabActor's windows.
+ *
+ * - Dedicated observers: There's only one of them for now: ReflowObserver which
+ *   listens to reflow events via the docshell,
+ *   These dedicated classes are used by the LayoutChangesObserver.
+ */
+
+const {Ci} = require("chrome");
+const {XPCOMUtils} = require("resource://gre/modules/XPCOMUtils.jsm");
+const protocol = require("devtools/shared/protocol");
+const {method, Arg} = protocol;
+const events = require("sdk/event/core");
+const Heritage = require("sdk/core/heritage");
+const EventEmitter = require("devtools/shared/event-emitter");
+const {reflowSpec} = require("devtools/shared/specs/reflow");
+
+/**
+ * The reflow actor tracks reflows and emits events about them.
+ */
+var ReflowActor = exports.ReflowActor = protocol.ActorClassWithSpec(reflowSpec, {
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+
+    this.tabActor = tabActor;
+    this._onReflow = this._onReflow.bind(this);
+    this.observer = getLayoutChangesObserver(tabActor);
+    this._isStarted = false;
+  },
+
+  /**
+   * The reflow actor is the first (and last) in its hierarchy to use
+   * protocol.js so it doesn't have a parent protocol actor that takes care of
+   * its lifetime. So it needs a disconnect method to cleanup.
+   */
+  disconnect: function () {
+    this.destroy();
+  },
+
+  destroy: function () {
+    this.stop();
+    releaseLayoutChangesObserver(this.tabActor);
+    this.observer = null;
+    this.tabActor = null;
+
+    protocol.Actor.prototype.destroy.call(this);
+  },
+
+  /**
+   * Start tracking reflows and sending events to clients about them.
+   * This is a oneway method, do not expect a response and it won't return a
+   * promise.
+   */
+  start: function () {
+    if (!this._isStarted) {
+      this.observer.on("reflows", this._onReflow);
+      this._isStarted = true;
+    }
+  },
+
+  /**
+   * Stop tracking reflows and sending events to clients about them.
+   * This is a oneway method, do not expect a response and it won't return a
+   * promise.
+   */
+  stop: function () {
+    if (this._isStarted) {
+      this.observer.off("reflows", this._onReflow);
+      this._isStarted = false;
+    }
+  },
+
+  _onReflow: function (event, reflows) {
+    if (this._isStarted) {
+      events.emit(this, "reflows", reflows);
+    }
+  }
+});
+
+/**
+ * Base class for all sorts of observers that need to listen to events on the
+ * tabActor's windows.
+ * @param {TabActor} tabActor
+ * @param {Function} callback Executed everytime the observer observes something
+ */
+function Observable(tabActor, callback) {
+  this.tabActor = tabActor;
+  this.callback = callback;
+
+  this._onWindowReady = this._onWindowReady.bind(this);
+  this._onWindowDestroyed = this._onWindowDestroyed.bind(this);
+
+  events.on(this.tabActor, "window-ready", this._onWindowReady);
+  events.on(this.tabActor, "window-destroyed", this._onWindowDestroyed);
+}
+
+Observable.prototype = {
+  /**
+   * Is the observer currently observing
+   */
+  isObserving: false,
+
+  /**
+   * Stop observing and detroy this observer instance
+   */
+  destroy: function () {
+    if (this.isDestroyed) {
+      return;
+    }
+    this.isDestroyed = true;
+
+    this.stop();
+
+    events.off(this.tabActor, "window-ready", this._onWindowReady);
+    events.off(this.tabActor, "window-destroyed", this._onWindowDestroyed);
+
+    this.callback = null;
+    this.tabActor = null;
+  },
+
+  /**
+   * Start observing whatever it is this observer is supposed to observe
+   */
+  start: function () {
+    if (this.isObserving) {
+      return;
+    }
+    this.isObserving = true;
+
+    this._startListeners(this.tabActor.windows);
+  },
+
+  /**
+   * Stop observing
+   */
+  stop: function () {
+    if (!this.isObserving) {
+      return;
+    }
+    this.isObserving = false;
+
+    if (this.tabActor.attached && this.tabActor.docShell) {
+      // It's only worth stopping if the tabActor is still attached
+      this._stopListeners(this.tabActor.windows);
+    }
+  },
+
+  _onWindowReady: function ({window}) {
+    if (this.isObserving) {
+      this._startListeners([window]);
+    }
+  },
+
+  _onWindowDestroyed: function ({window}) {
+    if (this.isObserving) {
+      this._stopListeners([window]);
+    }
+  },
+
+  _startListeners: function (windows) {
+    // To be implemented by sub-classes.
+  },
+
+  _stopListeners: function (windows) {
+    // To be implemented by sub-classes.
+  },
+
+  /**
+   * To be called by sub-classes when something has been observed
+   */
+  notifyCallback: function (...args) {
+    this.isObserving && this.callback && this.callback.apply(null, args);
+  }
+};
+
+/**
+ * The LayouChangesObserver will observe reflows as soon as it is started.
+ * Some devtools actors may cause reflows and it may be wanted to "hide" these
+ * reflows from the LayouChangesObserver consumers.
+ * If this is the case, such actors should require this module and use this
+ * global function to turn the ignore mode on and off temporarily.
+ *
+ * Note that if a node is provided, it will be used to force a sync reflow to
+ * make sure all reflows which occurred before switching the mode on or off are
+ * either observed or ignored depending on the current mode.
+ *
+ * @param {Boolean} ignore
+ * @param {DOMNode} syncReflowNode The node to use to force a sync reflow
+ */
+var gIgnoreLayoutChanges = false;
+exports.setIgnoreLayoutChanges = function (ignore, syncReflowNode) {
+  if (syncReflowNode) {
+    let forceSyncReflow = syncReflowNode.offsetWidth;
+  }
+  gIgnoreLayoutChanges = ignore;
+};
+
+/**
+ * The LayoutChangesObserver class is instantiated only once per given tab
+ * and is used to track reflows and dom and style changes in that tab.
+ * The LayoutActor uses this class to send reflow events to its clients.
+ *
+ * This class isn't exported on the module because it shouldn't be instantiated
+ * to avoid creating several instances per tabs.
+ * Use `getLayoutChangesObserver(tabActor)`
+ * and `releaseLayoutChangesObserver(tabActor)`
+ * which are exported to get and release instances.
+ *
+ * The observer loops every EVENT_BATCHING_DELAY ms and checks if layout changes
+ * have happened since the last loop iteration. If there are, it sends the
+ * corresponding events:
+ *
+ * - "reflows", with an array of all the reflows that occured,
+ * - "resizes", with an array of all the resizes that occured,
+ *
+ * @param {TabActor} tabActor
+ */
+function LayoutChangesObserver(tabActor) {
+  this.tabActor = tabActor;
+
+  this._startEventLoop = this._startEventLoop.bind(this);
+  this._onReflow = this._onReflow.bind(this);
+  this._onResize = this._onResize.bind(this);
+
+  // Creating the various observers we're going to need
+  // For now, just the reflow observer, but later we can add markupMutation,
+  // styleSheetChanges and styleRuleChanges
+  this.reflowObserver = new ReflowObserver(this.tabActor, this._onReflow);
+  this.resizeObserver = new WindowResizeObserver(this.tabActor, this._onResize);
+
+  EventEmitter.decorate(this);
+}
+
+exports.LayoutChangesObserver = LayoutChangesObserver;
+
+LayoutChangesObserver.prototype = {
+  /**
+   * How long does this observer waits before emitting batched events.
+   * The lower the value, the more event packets will be sent to clients,
+   * potentially impacting performance.
+   * The higher the value, the more time we'll wait, this is better for
+   * performance but has an effect on how soon changes are shown in the toolbox.
+   */
+  EVENT_BATCHING_DELAY: 300,
+
+  /**
+   * Destroying this instance of LayoutChangesObserver will stop the batched
+   * events from being sent.
+   */
+  destroy: function () {
+    this.isObserving = false;
+
+    this.reflowObserver.destroy();
+    this.reflows = null;
+
+    this.resizeObserver.destroy();
+    this.hasResized = false;
+
+    this.tabActor = null;
+  },
+
+  start: function () {
+    if (this.isObserving) {
+      return;
+    }
+    this.isObserving = true;
+
+    this.reflows = [];
+    this.hasResized = false;
+
+    this._startEventLoop();
+
+    this.reflowObserver.start();
+    this.resizeObserver.start();
+  },
+
+  stop: function () {
+    if (!this.isObserving) {
+      return;
+    }
+    this.isObserving = false;
+
+    this._stopEventLoop();
+
+    this.reflows = [];
+    this.hasResized = false;
+
+    this.reflowObserver.stop();
+    this.resizeObserver.stop();
+  },
+
+  /**
+   * Start the event loop, which regularly checks if there are any observer
+   * events to be sent as batched events
+   * Calls itself in a loop.
+   */
+  _startEventLoop: function () {
+    // Avoid emitting events if the tabActor has been detached (may happen
+    // during shutdown)
+    if (!this.tabActor || !this.tabActor.attached) {
+      return;
+    }
+
+    // Send any reflows we have
+    if (this.reflows && this.reflows.length) {
+      this.emit("reflows", this.reflows);
+      this.reflows = [];
+    }
+
+    // Send any resizes we have
+    if (this.hasResized) {
+      this.emit("resize");
+      this.hasResized = false;
+    }
+
+    this.eventLoopTimer = this._setTimeout(this._startEventLoop,
+      this.EVENT_BATCHING_DELAY);
+  },
+
+  _stopEventLoop: function () {
+    this._clearTimeout(this.eventLoopTimer);
+  },
+
+  // Exposing set/clearTimeout here to let tests override them if needed
+  _setTimeout: function (cb, ms) {
+    return setTimeout(cb, ms);
+  },
+  _clearTimeout: function (t) {
+    return clearTimeout(t);
+  },
+
+  /**
+   * Executed whenever a reflow is observed. Only stacks the reflow in the
+   * reflows array.
+   * The EVENT_BATCHING_DELAY loop will take care of it later.
+   * @param {Number} start When the reflow started
+   * @param {Number} end When the reflow ended
+   * @param {Boolean} isInterruptible
+   */
+  _onReflow: function (start, end, isInterruptible) {
+    if (gIgnoreLayoutChanges) {
+      return;
+    }
+
+    // XXX: when/if bug 997092 gets fixed, we will be able to know which
+    // elements have been reflowed, which would be a nice thing to add here.
+    this.reflows.push({
+      start: start,
+      end: end,
+      isInterruptible: isInterruptible
+    });
+  },
+
+  /**
+   * Executed whenever a resize is observed. Only store a flag saying that a
+   * resize occured.
+   * The EVENT_BATCHING_DELAY loop will take care of it later.
+   */
+  _onResize: function () {
+    if (gIgnoreLayoutChanges) {
+      return;
+    }
+
+    this.hasResized = true;
+  }
+};
+
+/**
+ * Get a LayoutChangesObserver instance for a given window. This function makes
+ * sure there is only one instance per window.
+ * @param {TabActor} tabActor
+ * @return {LayoutChangesObserver}
+ */
+var observedWindows = new Map();
+function getLayoutChangesObserver(tabActor) {
+  let observerData = observedWindows.get(tabActor);
+  if (observerData) {
+    observerData.refCounting ++;
+    return observerData.observer;
+  }
+
+  let obs = new LayoutChangesObserver(tabActor);
+  observedWindows.set(tabActor, {
+    observer: obs,
+    // counting references allows to stop the observer when no tabActor owns an
+    // instance.
+    refCounting: 1
+  });
+  obs.start();
+  return obs;
+}
+exports.getLayoutChangesObserver = getLayoutChangesObserver;
+
+/**
+ * Release a LayoutChangesObserver instance that was retrieved by
+ * getLayoutChangesObserver. This is required to ensure the tabActor reference
+ * is removed and the observer is eventually stopped and destroyed.
+ * @param {TabActor} tabActor
+ */
+function releaseLayoutChangesObserver(tabActor) {
+  let observerData = observedWindows.get(tabActor);
+  if (!observerData) {
+    return;
+  }
+
+  observerData.refCounting --;
+  if (!observerData.refCounting) {
+    observerData.observer.destroy();
+    observedWindows.delete(tabActor);
+  }
+}
+exports.releaseLayoutChangesObserver = releaseLayoutChangesObserver;
+
+/**
+ * Reports any reflow that occurs in the tabActor's docshells.
+ * @extends Observable
+ * @param {TabActor} tabActor
+ * @param {Function} callback Executed everytime a reflow occurs
+ */
+function ReflowObserver(tabActor, callback) {
+  Observable.call(this, tabActor, callback);
+}
+
+ReflowObserver.prototype = Heritage.extend(Observable.prototype, {
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIReflowObserver,
+    Ci.nsISupportsWeakReference]),
+
+  _startListeners: function (windows) {
+    for (let window of windows) {
+      let docshell = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                     .getInterface(Ci.nsIWebNavigation)
+                     .QueryInterface(Ci.nsIDocShell);
+      docshell.addWeakReflowObserver(this);
+    }
+  },
+
+  _stopListeners: function (windows) {
+    for (let window of windows) {
+      try {
+        let docshell = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                       .getInterface(Ci.nsIWebNavigation)
+                       .QueryInterface(Ci.nsIDocShell);
+        docshell.removeWeakReflowObserver(this);
+      } catch (e) {
+        // Corner cases where a global has already been freed may happen, in
+        // which case, no need to remove the observer.
+      }
+    }
+  },
+
+  reflow: function (start, end) {
+    this.notifyCallback(start, end, false);
+  },
+
+  reflowInterruptible: function (start, end) {
+    this.notifyCallback(start, end, true);
+  }
+});
+
+/**
+ * Reports window resize events on the tabActor's windows.
+ * @extends Observable
+ * @param {TabActor} tabActor
+ * @param {Function} callback Executed everytime a resize occurs
+ */
+function WindowResizeObserver(tabActor, callback) {
+  Observable.call(this, tabActor, callback);
+  this.onResize = this.onResize.bind(this);
+}
+
+WindowResizeObserver.prototype = Heritage.extend(Observable.prototype, {
+  _startListeners: function () {
+    this.listenerTarget.addEventListener("resize", this.onResize);
+  },
+
+  _stopListeners: function () {
+    this.listenerTarget.removeEventListener("resize", this.onResize);
+  },
+
+  onResize: function () {
+    this.notifyCallback();
+  },
+
+  get listenerTarget() {
+    // For the rootActor, return its window.
+    if (this.tabActor.isRootActor) {
+      return this.tabActor.window;
+    }
+
+    // Otherwise, get the tabActor's chromeEventHandler.
+    return this.tabActor.window.QueryInterface(Ci.nsIInterfaceRequestor)
+                               .getInterface(Ci.nsIWebNavigation)
+                               .QueryInterface(Ci.nsIDocShell)
+                               .chromeEventHandler;
+  }
+});
diff --git a/devtools/server/actors/root.js b/devtools/server/actors/root.js
new file mode 100644
index 000000000..b6f8c0ee4
--- /dev/null
+++ b/devtools/server/actors/root.js
@@ -0,0 +1,535 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cc, Ci, Cu } = require("chrome");
+const Services = require("Services");
+const { ActorPool, appendExtraActors, createExtraActors } = require("devtools/server/actors/common");
+const { DebuggerServer } = require("devtools/server/main");
+
+loader.lazyGetter(this, "ppmm", () => {
+  return Cc["@mozilla.org/parentprocessmessagemanager;1"].getService(Ci.nsIMessageBroadcaster);
+});
+
+/* Root actor for the remote debugging protocol. */
+
+/**
+ * Create a remote debugging protocol root actor.
+ *
+ * @param aConnection
+ *     The DebuggerServerConnection whose root actor we are constructing.
+ *
+ * @param aParameters
+ *     The properties of |aParameters| provide backing objects for the root
+ *     actor's requests; if a given property is omitted from |aParameters|, the
+ *     root actor won't implement the corresponding requests or notifications.
+ *     Supported properties:
+ *
+ *     - tabList: a live list (see below) of tab actors. If present, the
+ *       new root actor supports the 'listTabs' request, providing the live
+ *       list's elements as its tab actors, and sending 'tabListChanged'
+ *       notifications when the live list's contents change. One actor in
+ *       this list must have a true '.selected' property.
+ *
+ *     - addonList: a live list (see below) of addon actors. If present, the
+ *       new root actor supports the 'listAddons' request, providing the live
+ *       list's elements as its addon actors, and sending 'addonListchanged'
+ *       notifications when the live list's contents change.
+ *
+ *     - globalActorFactories: an object |A| describing further actors to
+ *       attach to the 'listTabs' reply. This is the type accumulated by
+ *       DebuggerServer.addGlobalActor. For each own property |P| of |A|,
+ *       the root actor adds a property named |P| to the 'listTabs'
+ *       reply whose value is the name of an actor constructed by
+ *       |A[P]|.
+ *
+ *     - onShutdown: a function to call when the root actor is disconnected.
+ *
+ * Instance properties:
+ *
+ * - applicationType: the string the root actor will include as the
+ *      "applicationType" property in the greeting packet. By default, this
+ *      is "browser".
+ *
+ * Live lists:
+ *
+ * A "live list", as used for the |tabList|, is an object that presents a
+ * list of actors, and also notifies its clients of changes to the list. A
+ * live list's interface is two properties:
+ *
+ * - getList: a method that returns a promise to the contents of the list.
+ *
+ * - onListChanged: a handler called, with no arguments, when the set of
+ *             values the iterator would produce has changed since the last
+ *             time 'iterator' was called. This may only be set to null or a
+ *             callable value (one for which the typeof operator returns
+ *             'function'). (Note that the live list will not call the
+ *             onListChanged handler until the list has been iterated over
+ *             once; if nobody's seen the list in the first place, nobody
+ *             should care if its contents have changed!)
+ *
+ * When the list changes, the list implementation should ensure that any
+ * actors yielded in previous iterations whose referents (tabs) still exist
+ * get yielded again in subsequent iterations. If the underlying referent
+ * is the same, the same actor should be presented for it.
+ *
+ * The root actor registers an 'onListChanged' handler on the appropriate
+ * list when it may need to send the client 'tabListChanged' notifications,
+ * and is careful to remove the handler whenever it does not need to send
+ * such notifications (including when it is disconnected). This means that
+ * live list implementations can use the state of the handler property (set
+ * or null) to install and remove observers and event listeners.
+ *
+ * Note that, as the only way for the root actor to see the members of the
+ * live list is to begin an iteration over the list, the live list need not
+ * actually produce any actors until they are reached in the course of
+ * iteration: alliterative lazy live lists.
+ */
+function RootActor(aConnection, aParameters) {
+  this.conn = aConnection;
+  this._parameters = aParameters;
+  this._onTabListChanged = this.onTabListChanged.bind(this);
+  this._onAddonListChanged = this.onAddonListChanged.bind(this);
+  this._onWorkerListChanged = this.onWorkerListChanged.bind(this);
+  this._onServiceWorkerRegistrationListChanged = this.onServiceWorkerRegistrationListChanged.bind(this);
+  this._onProcessListChanged = this.onProcessListChanged.bind(this);
+  this._extraActors = {};
+
+  this._globalActorPool = new ActorPool(this.conn);
+  this.conn.addActorPool(this._globalActorPool);
+
+  this._chromeActor = null;
+}
+
+RootActor.prototype = {
+  constructor: RootActor,
+  applicationType: "browser",
+
+  traits: {
+    sources: true,
+    // Whether the inspector actor allows modifying outer HTML.
+    editOuterHTML: true,
+    // Whether the inspector actor allows modifying innerHTML and inserting
+    // adjacent HTML.
+    pasteHTML: true,
+    // Whether the server-side highlighter actor exists and can be used to
+    // remotely highlight nodes (see server/actors/highlighters.js)
+    highlightable: true,
+    // Which custom highlighter does the server-side highlighter actor supports?
+    // (see server/actors/highlighters.js)
+    customHighlighters: true,
+    // Whether the inspector actor implements the getImageDataFromURL
+    // method that returns data-uris for image URLs. This is used for image
+    // tooltips for instance
+    urlToImageDataResolver: true,
+    networkMonitor: true,
+    // Whether the storage inspector actor to inspect cookies, etc.
+    storageInspector: true,
+    // Whether storage inspector is read only
+    storageInspectorReadOnly: true,
+    // Whether conditional breakpoints are supported
+    conditionalBreakpoints: true,
+    // Whether the server supports full source actors (breakpoints on
+    // eval scripts, etc)
+    debuggerSourceActors: true,
+    bulk: true,
+    // Whether the style rule actor implements the modifySelector method
+    // that modifies the rule's selector
+    selectorEditable: true,
+    // Whether the page style actor implements the addNewRule method that
+    // adds new rules to the page
+    addNewRule: true,
+    // Whether the dom node actor implements the getUniqueSelector method
+    getUniqueSelector: true,
+    // Whether the director scripts are supported
+    directorScripts: true,
+    // Whether the debugger server supports
+    // blackboxing/pretty-printing (not supported in Fever Dream yet)
+    noBlackBoxing: false,
+    noPrettyPrinting: false,
+    // Whether the page style actor implements the getUsedFontFaces method
+    // that returns the font faces used on a node
+    getUsedFontFaces: true,
+    // Trait added in Gecko 38, indicating that all features necessary for
+    // grabbing allocations from the MemoryActor are available for the performance tool
+    memoryActorAllocations: true,
+    // Added in Gecko 40, indicating that the backend isn't stupid about
+    // sending resumption packets on tab navigation.
+    noNeedToFakeResumptionOnNavigation: true,
+    // Added in Firefox 40. Indicates that the backend supports registering custom
+    // commands through the WebConsoleCommands API.
+    webConsoleCommands: true,
+    // Whether root actor exposes tab actors
+    // if allowChromeProcess is true, you can fetch a ChromeActor instance
+    // to debug chrome and any non-content ressource via getProcess request
+    // if allocChromeProcess is defined, but not true, it means that root actor
+    // no longer expose tab actors, but also that getProcess forbids
+    // exposing actors for security reasons
+    get allowChromeProcess() {
+      return DebuggerServer.allowChromeProcess;
+    },
+    // Whether or not `getProfile()` supports specifying a `startTime`
+    // and `endTime` to filter out samples. Fx40+
+    profilerDataFilterable: true,
+    // Whether or not the MemoryActor's heap snapshot abilities are
+    // fully equipped to handle heap snapshots for the memory tool. Fx44+
+    heapSnapshots: true,
+    // Whether or not the timeline actor can emit DOMContentLoaded and Load
+    // markers, currently in use by the network monitor. Fx45+
+    documentLoadingMarkers: true
+  },
+
+  /**
+   * Return a 'hello' packet as specified by the Remote Debugging Protocol.
+   */
+  sayHello: function () {
+    return {
+      from: this.actorID,
+      applicationType: this.applicationType,
+      /* This is not in the spec, but it's used by tests. */
+      testConnectionPrefix: this.conn.prefix,
+      traits: this.traits
+    };
+  },
+
+  forwardingCancelled: function (prefix) {
+    return {
+      from: this.actorID,
+      type: "forwardingCancelled",
+      prefix,
+    };
+  },
+
+  /**
+   * Disconnects the actor from the browser window.
+   */
+  disconnect: function () {
+    /* Tell the live lists we aren't watching any more. */
+    if (this._parameters.tabList) {
+      this._parameters.tabList.onListChanged = null;
+    }
+    if (this._parameters.addonList) {
+      this._parameters.addonList.onListChanged = null;
+    }
+    if (this._parameters.workerList) {
+      this._parameters.workerList.onListChanged = null;
+    }
+    if (this._parameters.serviceWorkerRegistrationList) {
+      this._parameters.serviceWorkerRegistrationList.onListChanged = null;
+    }
+    if (typeof this._parameters.onShutdown === "function") {
+      this._parameters.onShutdown();
+    }
+    this._extraActors = null;
+    this.conn = null;
+    this._tabActorPool = null;
+    this._globalActorPool = null;
+    this._parameters = null;
+    this._chromeActor = null;
+  },
+
+  /* The 'listTabs' request and the 'tabListChanged' notification. */
+
+  /**
+   * Handles the listTabs request. The actors will survive until at least
+   * the next listTabs request.
+   */
+  onListTabs: function () {
+    let tabList = this._parameters.tabList;
+    if (!tabList) {
+      return { from: this.actorID, error: "noTabs",
+               message: "This root actor has no browser tabs." };
+    }
+
+    /*
+     * Walk the tab list, accumulating the array of tab actors for the
+     * reply, and moving all the actors to a new ActorPool. We'll
+     * replace the old tab actor pool with the one we build here, thus
+     * retiring any actors that didn't get listed again, and preparing any
+     * new actors to receive packets.
+     */
+    let newActorPool = new ActorPool(this.conn);
+    let tabActorList = [];
+    let selected;
+    return tabList.getList().then((tabActors) => {
+      for (let tabActor of tabActors) {
+        if (tabActor.selected) {
+          selected = tabActorList.length;
+        }
+        tabActor.parentID = this.actorID;
+        newActorPool.addActor(tabActor);
+        tabActorList.push(tabActor);
+      }
+      /* DebuggerServer.addGlobalActor support: create actors. */
+      if (!this._globalActorPool) {
+        this._globalActorPool = new ActorPool(this.conn);
+        this.conn.addActorPool(this._globalActorPool);
+      }
+      this._createExtraActors(this._parameters.globalActorFactories, this._globalActorPool);
+      /*
+       * Drop the old actorID -> actor map. Actors that still mattered were
+       * added to the new map; others will go away.
+       */
+      if (this._tabActorPool) {
+        this.conn.removeActorPool(this._tabActorPool);
+      }
+      this._tabActorPool = newActorPool;
+      this.conn.addActorPool(this._tabActorPool);
+
+      let reply = {
+        "from": this.actorID,
+        "selected": selected || 0,
+        "tabs": tabActorList.map(actor => actor.form())
+      };
+
+      /* If a root window is accessible, include its URL. */
+      if (this.url) {
+        reply.url = this.url;
+      }
+
+      /* DebuggerServer.addGlobalActor support: name actors in 'listTabs' reply. */
+      this._appendExtraActors(reply);
+
+      /*
+       * Now that we're actually going to report the contents of tabList to
+       * the client, we're responsible for letting the client know if it
+       * changes.
+       */
+      tabList.onListChanged = this._onTabListChanged;
+
+      return reply;
+    });
+  },
+
+  onGetTab: function (options) {
+    let tabList = this._parameters.tabList;
+    if (!tabList) {
+      return { error: "noTabs",
+               message: "This root actor has no browser tabs." };
+    }
+    if (!this._tabActorPool) {
+      this._tabActorPool = new ActorPool(this.conn);
+      this.conn.addActorPool(this._tabActorPool);
+    }
+    return tabList.getTab(options)
+                  .then(tabActor => {
+                    tabActor.parentID = this.actorID;
+                    this._tabActorPool.addActor(tabActor);
+
+                    return { tab: tabActor.form() };
+                  }, error => {
+                    if (error.error) {
+        // Pipe expected errors as-is to the client
+                      return error;
+                    } else {
+                      return { error: "noTab",
+                 message: "Unexpected error while calling getTab(): " + error };
+                    }
+                  });
+  },
+
+  onTabListChanged: function () {
+    this.conn.send({ from: this.actorID, type:"tabListChanged" });
+    /* It's a one-shot notification; no need to watch any more. */
+    this._parameters.tabList.onListChanged = null;
+  },
+
+  onListAddons: function () {
+    let addonList = this._parameters.addonList;
+    if (!addonList) {
+      return { from: this.actorID, error: "noAddons",
+               message: "This root actor has no browser addons." };
+    }
+
+    return addonList.getList().then((addonActors) => {
+      let addonActorPool = new ActorPool(this.conn);
+      for (let addonActor of addonActors) {
+        addonActorPool.addActor(addonActor);
+      }
+
+      if (this._addonActorPool) {
+        this.conn.removeActorPool(this._addonActorPool);
+      }
+      this._addonActorPool = addonActorPool;
+      this.conn.addActorPool(this._addonActorPool);
+
+      addonList.onListChanged = this._onAddonListChanged;
+
+      return {
+        "from": this.actorID,
+        "addons": addonActors.map(addonActor => addonActor.form())
+      };
+    });
+  },
+
+  onAddonListChanged: function () {
+    this.conn.send({ from: this.actorID, type: "addonListChanged" });
+    this._parameters.addonList.onListChanged = null;
+  },
+
+  onListWorkers: function () {
+    let workerList = this._parameters.workerList;
+    if (!workerList) {
+      return { from: this.actorID, error: "noWorkers",
+               message: "This root actor has no workers." };
+    }
+
+    return workerList.getList().then(actors => {
+      let pool = new ActorPool(this.conn);
+      for (let actor of actors) {
+        pool.addActor(actor);
+      }
+
+      this.conn.removeActorPool(this._workerActorPool);
+      this._workerActorPool = pool;
+      this.conn.addActorPool(this._workerActorPool);
+
+      workerList.onListChanged = this._onWorkerListChanged;
+
+      return {
+        "from": this.actorID,
+        "workers": actors.map(actor => actor.form())
+      };
+    });
+  },
+
+  onWorkerListChanged: function () {
+    this.conn.send({ from: this.actorID, type: "workerListChanged" });
+    this._parameters.workerList.onListChanged = null;
+  },
+
+  onListServiceWorkerRegistrations: function () {
+    let registrationList = this._parameters.serviceWorkerRegistrationList;
+    if (!registrationList) {
+      return { from: this.actorID, error: "noServiceWorkerRegistrations",
+               message: "This root actor has no service worker registrations." };
+    }
+
+    return registrationList.getList().then(actors => {
+      let pool = new ActorPool(this.conn);
+      for (let actor of actors) {
+        pool.addActor(actor);
+      }
+
+      this.conn.removeActorPool(this._serviceWorkerRegistrationActorPool);
+      this._serviceWorkerRegistrationActorPool = pool;
+      this.conn.addActorPool(this._serviceWorkerRegistrationActorPool);
+
+      registrationList.onListChanged = this._onServiceWorkerRegistrationListChanged;
+
+      return {
+        "from": this.actorID,
+        "registrations": actors.map(actor => actor.form())
+      };
+    });
+  },
+
+  onServiceWorkerRegistrationListChanged: function () {
+    this.conn.send({ from: this.actorID, type: "serviceWorkerRegistrationListChanged" });
+    this._parameters.serviceWorkerRegistrationList.onListChanged = null;
+  },
+
+  onListProcesses: function () {
+    let { processList } = this._parameters;
+    if (!processList) {
+      return { from: this.actorID, error: "noProcesses",
+               message: "This root actor has no processes." };
+    }
+    processList.onListChanged = this._onProcessListChanged;
+    return {
+      processes: processList.getList()
+    };
+  },
+
+  onProcessListChanged: function () {
+    this.conn.send({ from: this.actorID, type: "processListChanged" });
+    this._parameters.processList.onListChanged = null;
+  },
+
+  onGetProcess: function (aRequest) {
+    if (!DebuggerServer.allowChromeProcess) {
+      return { error: "forbidden",
+               message: "You are not allowed to debug chrome." };
+    }
+    if (("id" in aRequest) && typeof (aRequest.id) != "number") {
+      return { error: "wrongParameter",
+               message: "getProcess requires a valid `id` attribute." };
+    }
+    // If the request doesn't contains id parameter or id is 0
+    // (id == 0, based on onListProcesses implementation)
+    if ((!("id" in aRequest)) || aRequest.id === 0) {
+      if (!this._chromeActor) {
+        // Create a ChromeActor for the parent process
+        let { ChromeActor } = require("devtools/server/actors/chrome");
+        this._chromeActor = new ChromeActor(this.conn);
+        this._globalActorPool.addActor(this._chromeActor);
+      }
+
+      return { form: this._chromeActor.form() };
+    } else {
+      let mm = ppmm.getChildAt(aRequest.id);
+      if (!mm) {
+        return { error: "noProcess",
+                 message: "There is no process with id '" + aRequest.id + "'." };
+      }
+      return DebuggerServer.connectToContent(this.conn, mm)
+                           .then(form => ({ form }));
+    }
+  },
+
+  /* This is not in the spec, but it's used by tests. */
+  onEcho: function (aRequest) {
+    /*
+     * Request packets are frozen. Copy aRequest, so that
+     * DebuggerServerConnection.onPacket can attach a 'from' property.
+     */
+    return Cu.cloneInto(aRequest, {});
+  },
+
+  onProtocolDescription: function () {
+    return require("devtools/shared/protocol").dumpProtocolSpec();
+  },
+
+  /* Support for DebuggerServer.addGlobalActor. */
+  _createExtraActors: createExtraActors,
+  _appendExtraActors: appendExtraActors,
+
+  /**
+   * Remove the extra actor (added by DebuggerServer.addGlobalActor or
+   * DebuggerServer.addTabActor) name |aName|.
+   */
+  removeActorByName: function (aName) {
+    if (aName in this._extraActors) {
+      const actor = this._extraActors[aName];
+      if (this._globalActorPool.has(actor)) {
+        this._globalActorPool.removeActor(actor);
+      }
+      if (this._tabActorPool) {
+        // Iterate over TabActor instances to also remove tab actors
+        // created during listTabs for each document.
+        this._tabActorPool.forEach(tab => {
+          tab.removeActorByName(aName);
+        });
+      }
+      delete this._extraActors[aName];
+    }
+  }
+};
+
+RootActor.prototype.requestTypes = {
+  "listTabs": RootActor.prototype.onListTabs,
+  "getTab": RootActor.prototype.onGetTab,
+  "listAddons": RootActor.prototype.onListAddons,
+  "listWorkers": RootActor.prototype.onListWorkers,
+  "listServiceWorkerRegistrations": RootActor.prototype.onListServiceWorkerRegistrations,
+  "listProcesses": RootActor.prototype.onListProcesses,
+  "getProcess": RootActor.prototype.onGetProcess,
+  "echo": RootActor.prototype.onEcho,
+  "protocolDescription": RootActor.prototype.onProtocolDescription
+};
+
+exports.RootActor = RootActor;
diff --git a/devtools/server/actors/script.js b/devtools/server/actors/script.js
new file mode 100644
index 000000000..e8e39546c
--- /dev/null
+++ b/devtools/server/actors/script.js
@@ -0,0 +1,2360 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const Services = require("Services");
+const { Cc, Ci, Cu, Cr, components, ChromeWorker } = require("chrome");
+const { ActorPool, OriginalLocation, GeneratedLocation } = require("devtools/server/actors/common");
+const { BreakpointActor, setBreakpointAtEntryPoints } = require("devtools/server/actors/breakpoint");
+const { EnvironmentActor } = require("devtools/server/actors/environment");
+const { FrameActor } = require("devtools/server/actors/frame");
+const { ObjectActor, createValueGrip, longStringGrip } = require("devtools/server/actors/object");
+const { SourceActor, getSourceURL } = require("devtools/server/actors/source");
+const { DebuggerServer } = require("devtools/server/main");
+const { ActorClassWithSpec } = require("devtools/shared/protocol");
+const DevToolsUtils = require("devtools/shared/DevToolsUtils");
+const flags = require("devtools/shared/flags");
+const { assert, dumpn, update, fetch } = DevToolsUtils;
+const promise = require("promise");
+const xpcInspector = require("xpcInspector");
+const { DevToolsWorker } = require("devtools/shared/worker/worker");
+const object = require("sdk/util/object");
+const { threadSpec } = require("devtools/shared/specs/script");
+
+const { defer, resolve, reject, all } = promise;
+
+loader.lazyGetter(this, "Debugger", () => {
+  let Debugger = require("Debugger");
+  hackDebugger(Debugger);
+  return Debugger;
+});
+loader.lazyRequireGetter(this, "CssLogic", "devtools/server/css-logic", true);
+loader.lazyRequireGetter(this, "events", "sdk/event/core");
+loader.lazyRequireGetter(this, "mapURIToAddonID", "devtools/server/actors/utils/map-uri-to-addon-id");
+
+/**
+ * A BreakpointActorMap is a map from locations to instances of BreakpointActor.
+ */
+function BreakpointActorMap() {
+  this._size = 0;
+  this._actors = {};
+}
+
+BreakpointActorMap.prototype = {
+  /**
+   * Return the number of BreakpointActors in this BreakpointActorMap.
+   *
+   * @returns Number
+   *          The number of BreakpointActor in this BreakpointActorMap.
+   */
+  get size() {
+    return this._size;
+  },
+
+  /**
+   * Generate all BreakpointActors that match the given location in
+   * this BreakpointActorMap.
+   *
+   * @param OriginalLocation location
+   *        The location for which matching BreakpointActors should be generated.
+   */
+  findActors: function* (location = new OriginalLocation()) {
+    // Fast shortcut for when we know we won't find any actors. Surprisingly
+    // enough, this speeds up refreshing when there are no breakpoints set by
+    // about 2x!
+    if (this.size === 0) {
+      return;
+    }
+
+    function* findKeys(object, key) {
+      if (key !== undefined) {
+        if (key in object) {
+          yield key;
+        }
+      }
+      else {
+        for (let key of Object.keys(object)) {
+          yield key;
+        }
+      }
+    }
+
+    let query = {
+      sourceActorID: location.originalSourceActor ? location.originalSourceActor.actorID : undefined,
+      line: location.originalLine,
+    };
+
+    // If location contains a line, assume we are searching for a whole line
+    // breakpoint, and set begin/endColumn accordingly. Otherwise, we are
+    // searching for all breakpoints, so begin/endColumn should be left unset.
+    if (location.originalLine) {
+      query.beginColumn = location.originalColumn ? location.originalColumn : 0;
+      query.endColumn = location.originalColumn ? location.originalColumn + 1 : Infinity;
+    } else {
+      query.beginColumn = location.originalColumn ? query.originalColumn : undefined;
+      query.endColumn = location.originalColumn ? query.originalColumn + 1 : undefined;
+    }
+
+    for (let sourceActorID of findKeys(this._actors, query.sourceActorID))
+      for (let line of findKeys(this._actors[sourceActorID], query.line))
+        for (let beginColumn of findKeys(this._actors[sourceActorID][line], query.beginColumn))
+          for (let endColumn of findKeys(this._actors[sourceActorID][line][beginColumn], query.endColumn)) {
+            yield this._actors[sourceActorID][line][beginColumn][endColumn];
+          }
+  },
+
+  /**
+   * Return the BreakpointActor at the given location in this
+   * BreakpointActorMap.
+   *
+   * @param OriginalLocation location
+   *        The location for which the BreakpointActor should be returned.
+   *
+   * @returns BreakpointActor actor
+   *          The BreakpointActor at the given location.
+   */
+  getActor: function (originalLocation) {
+    for (let actor of this.findActors(originalLocation)) {
+      return actor;
+    }
+
+    return null;
+  },
+
+  /**
+   * Set the given BreakpointActor to the given location in this
+   * BreakpointActorMap.
+   *
+   * @param OriginalLocation location
+   *        The location to which the given BreakpointActor should be set.
+   *
+   * @param BreakpointActor actor
+   *        The BreakpointActor to be set to the given location.
+   */
+  setActor: function (location, actor) {
+    let { originalSourceActor, originalLine, originalColumn } = location;
+
+    let sourceActorID = originalSourceActor.actorID;
+    let line = originalLine;
+    let beginColumn = originalColumn ? originalColumn : 0;
+    let endColumn = originalColumn ? originalColumn + 1 : Infinity;
+
+    if (!this._actors[sourceActorID]) {
+      this._actors[sourceActorID] = [];
+    }
+    if (!this._actors[sourceActorID][line]) {
+      this._actors[sourceActorID][line] = [];
+    }
+    if (!this._actors[sourceActorID][line][beginColumn]) {
+      this._actors[sourceActorID][line][beginColumn] = [];
+    }
+    if (!this._actors[sourceActorID][line][beginColumn][endColumn]) {
+      ++this._size;
+    }
+    this._actors[sourceActorID][line][beginColumn][endColumn] = actor;
+  },
+
+  /**
+   * Delete the BreakpointActor from the given location in this
+   * BreakpointActorMap.
+   *
+   * @param OriginalLocation location
+   *        The location from which the BreakpointActor should be deleted.
+   */
+  deleteActor: function (location) {
+    let { originalSourceActor, originalLine, originalColumn } = location;
+
+    let sourceActorID = originalSourceActor.actorID;
+    let line = originalLine;
+    let beginColumn = originalColumn ? originalColumn : 0;
+    let endColumn = originalColumn ? originalColumn + 1 : Infinity;
+
+    if (this._actors[sourceActorID]) {
+      if (this._actors[sourceActorID][line]) {
+        if (this._actors[sourceActorID][line][beginColumn]) {
+          if (this._actors[sourceActorID][line][beginColumn][endColumn]) {
+            --this._size;
+          }
+          delete this._actors[sourceActorID][line][beginColumn][endColumn];
+          if (Object.keys(this._actors[sourceActorID][line][beginColumn]).length === 0) {
+            delete this._actors[sourceActorID][line][beginColumn];
+          }
+        }
+        if (Object.keys(this._actors[sourceActorID][line]).length === 0) {
+          delete this._actors[sourceActorID][line];
+        }
+      }
+    }
+  }
+};
+
+exports.BreakpointActorMap = BreakpointActorMap;
+
+/**
+ * Keeps track of persistent sources across reloads and ties different
+ * source instances to the same actor id so that things like
+ * breakpoints survive reloads. ThreadSources uses this to force the
+ * same actorID on a SourceActor.
+ */
+function SourceActorStore() {
+  // source identifier --> actor id
+  this._sourceActorIds = Object.create(null);
+}
+
+SourceActorStore.prototype = {
+  /**
+   * Lookup an existing actor id that represents this source, if available.
+   */
+  getReusableActorId: function (aSource, aOriginalUrl) {
+    let url = this.getUniqueKey(aSource, aOriginalUrl);
+    if (url && url in this._sourceActorIds) {
+      return this._sourceActorIds[url];
+    }
+    return null;
+  },
+
+  /**
+   * Update a source with an actorID.
+   */
+  setReusableActorId: function (aSource, aOriginalUrl, actorID) {
+    let url = this.getUniqueKey(aSource, aOriginalUrl);
+    if (url) {
+      this._sourceActorIds[url] = actorID;
+    }
+  },
+
+  /**
+   * Make a unique URL from a source that identifies it across reloads.
+   */
+  getUniqueKey: function (aSource, aOriginalUrl) {
+    if (aOriginalUrl) {
+      // Original source from a sourcemap.
+      return aOriginalUrl;
+    }
+    else {
+      return getSourceURL(aSource);
+    }
+  }
+};
+
+exports.SourceActorStore = SourceActorStore;
+
+/**
+ * Manages pushing event loops and automatically pops and exits them in the
+ * correct order as they are resolved.
+ *
+ * @param ThreadActor thread
+ *        The thread actor instance that owns this EventLoopStack.
+ * @param DebuggerServerConnection connection
+ *        The remote protocol connection associated with this event loop stack.
+ * @param Object hooks
+ *        An object with the following properties:
+ *          - url: The URL string of the debuggee we are spinning an event loop
+ *                 for.
+ *          - preNest: function called before entering a nested event loop
+ *          - postNest: function called after exiting a nested event loop
+ */
+function EventLoopStack({ thread, connection, hooks }) {
+  this._hooks = hooks;
+  this._thread = thread;
+  this._connection = connection;
+}
+
+EventLoopStack.prototype = {
+  /**
+   * The number of nested event loops on the stack.
+   */
+  get size() {
+    return xpcInspector.eventLoopNestLevel;
+  },
+
+  /**
+   * The URL of the debuggee who pushed the event loop on top of the stack.
+   */
+  get lastPausedUrl() {
+    let url = null;
+    if (this.size > 0) {
+      try {
+        url = xpcInspector.lastNestRequestor.url;
+      } catch (e) {
+        // The tab's URL getter may throw if the tab is destroyed by the time
+        // this code runs, but we don't really care at this point.
+        dumpn(e);
+      }
+    }
+    return url;
+  },
+
+  /**
+   * The DebuggerServerConnection of the debugger who pushed the event loop on
+   * top of the stack
+   */
+  get lastConnection() {
+    return xpcInspector.lastNestRequestor._connection;
+  },
+
+  /**
+   * Push a new nested event loop onto the stack.
+   *
+   * @returns EventLoop
+   */
+  push: function () {
+    return new EventLoop({
+      thread: this._thread,
+      connection: this._connection,
+      hooks: this._hooks
+    });
+  }
+};
+
+/**
+ * An object that represents a nested event loop. It is used as the nest
+ * requestor with nsIJSInspector instances.
+ *
+ * @param ThreadActor thread
+ *        The thread actor that is creating this nested event loop.
+ * @param DebuggerServerConnection connection
+ *        The remote protocol connection associated with this event loop.
+ * @param Object hooks
+ *        The same hooks object passed into EventLoopStack during its
+ *        initialization.
+ */
+function EventLoop({ thread, connection, hooks }) {
+  this._thread = thread;
+  this._hooks = hooks;
+  this._connection = connection;
+
+  this.enter = this.enter.bind(this);
+  this.resolve = this.resolve.bind(this);
+}
+
+EventLoop.prototype = {
+  entered: false,
+  resolved: false,
+  get url() { return this._hooks.url; },
+
+  /**
+   * Enter this nested event loop.
+   */
+  enter: function () {
+    let nestData = this._hooks.preNest
+      ? this._hooks.preNest()
+      : null;
+
+    this.entered = true;
+    xpcInspector.enterNestedEventLoop(this);
+
+    // Keep exiting nested event loops while the last requestor is resolved.
+    if (xpcInspector.eventLoopNestLevel > 0) {
+      const { resolved } = xpcInspector.lastNestRequestor;
+      if (resolved) {
+        xpcInspector.exitNestedEventLoop();
+      }
+    }
+
+    if (this._hooks.postNest) {
+      this._hooks.postNest(nestData);
+    }
+  },
+
+  /**
+   * Resolve this nested event loop.
+   *
+   * @returns boolean
+   *          True if we exited this nested event loop because it was on top of
+   *          the stack, false if there is another nested event loop above this
+   *          one that hasn't resolved yet.
+   */
+  resolve: function () {
+    if (!this.entered) {
+      throw new Error("Can't resolve an event loop before it has been entered!");
+    }
+    if (this.resolved) {
+      throw new Error("Already resolved this nested event loop!");
+    }
+    this.resolved = true;
+    if (this === xpcInspector.lastNestRequestor) {
+      xpcInspector.exitNestedEventLoop();
+      return true;
+    }
+    return false;
+  },
+};
+
+/**
+ * JSD2 actors.
+ */
+
+/**
+ * Creates a ThreadActor.
+ *
+ * ThreadActors manage a JSInspector object and manage execution/inspection
+ * of debuggees.
+ *
+ * @param aParent object
+ *        This |ThreadActor|'s parent actor. It must implement the following
+ *        properties:
+ *          - url: The URL string of the debuggee.
+ *          - window: The global window object.
+ *          - preNest: Function called before entering a nested event loop.
+ *          - postNest: Function called after exiting a nested event loop.
+ *          - makeDebugger: A function that takes no arguments and instantiates
+ *            a Debugger that manages its globals on its own.
+ * @param aGlobal object [optional]
+ *        An optional (for content debugging only) reference to the content
+ *        window.
+ */
+const ThreadActor = ActorClassWithSpec(threadSpec, {
+  initialize: function (aParent, aGlobal) {
+    this._state = "detached";
+    this._frameActors = [];
+    this._parent = aParent;
+    this._dbg = null;
+    this._gripDepth = 0;
+    this._threadLifetimePool = null;
+    this._tabClosed = false;
+    this._scripts = null;
+    this._pauseOnDOMEvents = null;
+
+    this._options = {
+      useSourceMaps: false,
+      autoBlackBox: false
+    };
+
+    this.breakpointActorMap = new BreakpointActorMap();
+    this.sourceActorStore = new SourceActorStore();
+
+    this._debuggerSourcesSeen = null;
+
+    // A map of actorID -> actor for breakpoints created and managed by the
+    // server.
+    this._hiddenBreakpoints = new Map();
+
+    this.global = aGlobal;
+
+    this._allEventsListener = this._allEventsListener.bind(this);
+    this.onNewGlobal = this.onNewGlobal.bind(this);
+    this.onSourceEvent = this.onSourceEvent.bind(this);
+    this.uncaughtExceptionHook = this.uncaughtExceptionHook.bind(this);
+    this.onDebuggerStatement = this.onDebuggerStatement.bind(this);
+    this.onNewScript = this.onNewScript.bind(this);
+    this.objectGrip = this.objectGrip.bind(this);
+    this.pauseObjectGrip = this.pauseObjectGrip.bind(this);
+    this._onWindowReady = this._onWindowReady.bind(this);
+    events.on(this._parent, "window-ready", this._onWindowReady);
+    // Set a wrappedJSObject property so |this| can be sent via the observer svc
+    // for the xpcshell harness.
+    this.wrappedJSObject = this;
+  },
+
+  // Used by the ObjectActor to keep track of the depth of grip() calls.
+  _gripDepth: null,
+
+  get dbg() {
+    if (!this._dbg) {
+      this._dbg = this._parent.makeDebugger();
+      this._dbg.uncaughtExceptionHook = this.uncaughtExceptionHook;
+      this._dbg.onDebuggerStatement = this.onDebuggerStatement;
+      this._dbg.onNewScript = this.onNewScript;
+      this._dbg.on("newGlobal", this.onNewGlobal);
+      // Keep the debugger disabled until a client attaches.
+      this._dbg.enabled = this._state != "detached";
+    }
+    return this._dbg;
+  },
+
+  get globalDebugObject() {
+    if (!this._parent.window) {
+      return null;
+    }
+    return this.dbg.makeGlobalObjectReference(this._parent.window);
+  },
+
+  get state() {
+    return this._state;
+  },
+
+  get attached() {
+    return this.state == "attached" ||
+           this.state == "running" ||
+           this.state == "paused";
+  },
+
+  get threadLifetimePool() {
+    if (!this._threadLifetimePool) {
+      this._threadLifetimePool = new ActorPool(this.conn);
+      this.conn.addActorPool(this._threadLifetimePool);
+      this._threadLifetimePool.objectActors = new WeakMap();
+    }
+    return this._threadLifetimePool;
+  },
+
+  get sources() {
+    return this._parent.sources;
+  },
+
+  get youngestFrame() {
+    if (this.state != "paused") {
+      return null;
+    }
+    return this.dbg.getNewestFrame();
+  },
+
+  _prettyPrintWorker: null,
+  get prettyPrintWorker() {
+    if (!this._prettyPrintWorker) {
+      this._prettyPrintWorker = new DevToolsWorker(
+        "resource://devtools/server/actors/pretty-print-worker.js",
+        { name: "pretty-print",
+          verbose: flags.wantLogging }
+      );
+    }
+    return this._prettyPrintWorker;
+  },
+
+  /**
+   * Keep track of all of the nested event loops we use to pause the debuggee
+   * when we hit a breakpoint/debugger statement/etc in one place so we can
+   * resolve them when we get resume packets. We have more than one (and keep
+   * them in a stack) because we can pause within client evals.
+   */
+  _threadPauseEventLoops: null,
+  _pushThreadPause: function () {
+    if (!this._threadPauseEventLoops) {
+      this._threadPauseEventLoops = [];
+    }
+    const eventLoop = this._nestedEventLoops.push();
+    this._threadPauseEventLoops.push(eventLoop);
+    eventLoop.enter();
+  },
+  _popThreadPause: function () {
+    const eventLoop = this._threadPauseEventLoops.pop();
+    assert(eventLoop, "Should have an event loop.");
+    eventLoop.resolve();
+  },
+
+  /**
+   * Remove all debuggees and clear out the thread's sources.
+   */
+  clearDebuggees: function () {
+    if (this._dbg) {
+      this.dbg.removeAllDebuggees();
+    }
+    this._sources = null;
+    this._scripts = null;
+  },
+
+  /**
+   * Listener for our |Debugger|'s "newGlobal" event.
+   */
+  onNewGlobal: function (aGlobal) {
+    // Notify the client.
+    this.conn.send({
+      from: this.actorID,
+      type: "newGlobal",
+      // TODO: after bug 801084 lands see if we need to JSONify this.
+      hostAnnotations: aGlobal.hostAnnotations
+    });
+  },
+
+  disconnect: function () {
+    dumpn("in ThreadActor.prototype.disconnect");
+    if (this._state == "paused") {
+      this.onResume();
+    }
+
+    // Blow away our source actor ID store because those IDs are only
+    // valid for this connection. This is ok because we never keep
+    // things like breakpoints across connections.
+    this._sourceActorStore = null;
+
+    events.off(this._parent, "window-ready", this._onWindowReady);
+    this.sources.off("newSource", this.onSourceEvent);
+    this.sources.off("updatedSource", this.onSourceEvent);
+    this.clearDebuggees();
+    this.conn.removeActorPool(this._threadLifetimePool);
+    this._threadLifetimePool = null;
+
+    if (this._prettyPrintWorker) {
+      this._prettyPrintWorker.destroy();
+      this._prettyPrintWorker = null;
+    }
+
+    if (!this._dbg) {
+      return;
+    }
+    this._dbg.enabled = false;
+    this._dbg = null;
+  },
+
+  /**
+   * Disconnect the debugger and put the actor in the exited state.
+   */
+  exit: function () {
+    this.disconnect();
+    this._state = "exited";
+  },
+
+  // Request handlers
+  onAttach: function (aRequest) {
+    if (this.state === "exited") {
+      return { type: "exited" };
+    }
+
+    if (this.state !== "detached") {
+      return { error: "wrongState",
+               message: "Current state is " + this.state };
+    }
+
+    this._state = "attached";
+    this._debuggerSourcesSeen = new WeakSet();
+
+    Object.assign(this._options, aRequest.options || {});
+    this.sources.setOptions(this._options);
+    this.sources.on("newSource", this.onSourceEvent);
+    this.sources.on("updatedSource", this.onSourceEvent);
+
+    // Initialize an event loop stack. This can't be done in the constructor,
+    // because this.conn is not yet initialized by the actor pool at that time.
+    this._nestedEventLoops = new EventLoopStack({
+      hooks: this._parent,
+      connection: this.conn,
+      thread: this
+    });
+
+    this.dbg.addDebuggees();
+    this.dbg.enabled = true;
+    try {
+      // Put ourselves in the paused state.
+      let packet = this._paused();
+      if (!packet) {
+        return { error: "notAttached" };
+      }
+      packet.why = { type: "attached" };
+
+      // Send the response to the attach request now (rather than
+      // returning it), because we're going to start a nested event loop
+      // here.
+      this.conn.send(packet);
+
+      // Start a nested event loop.
+      this._pushThreadPause();
+
+      // We already sent a response to this request, don't send one
+      // now.
+      return null;
+    } catch (e) {
+      reportError(e);
+      return { error: "notAttached", message: e.toString() };
+    }
+  },
+
+  onDetach: function (aRequest) {
+    this.disconnect();
+    this._state = "detached";
+    this._debuggerSourcesSeen = null;
+
+    dumpn("ThreadActor.prototype.onDetach: returning 'detached' packet");
+    return {
+      type: "detached"
+    };
+  },
+
+  onReconfigure: function (aRequest) {
+    if (this.state == "exited") {
+      return { error: "wrongState" };
+    }
+    const options = aRequest.options || {};
+
+    if ("observeAsmJS" in options) {
+      this.dbg.allowUnobservedAsmJS = !options.observeAsmJS;
+    }
+
+    Object.assign(this._options, options);
+
+    // Update the global source store
+    this.sources.setOptions(options);
+
+    return {};
+  },
+
+  /**
+   * Pause the debuggee, by entering a nested event loop, and return a 'paused'
+   * packet to the client.
+   *
+   * @param Debugger.Frame aFrame
+   *        The newest debuggee frame in the stack.
+   * @param object aReason
+   *        An object with a 'type' property containing the reason for the pause.
+   * @param function onPacket
+   *        Hook to modify the packet before it is sent. Feel free to return a
+   *        promise.
+   */
+  _pauseAndRespond: function (aFrame, aReason, onPacket = function (k) { return k; }) {
+    try {
+      let packet = this._paused(aFrame);
+      if (!packet) {
+        return undefined;
+      }
+      packet.why = aReason;
+
+      let generatedLocation = this.sources.getFrameLocation(aFrame);
+      this.sources.getOriginalLocation(generatedLocation)
+                  .then((originalLocation) => {
+                    if (!originalLocation.originalSourceActor) {
+          // The only time the source actor will be null is if there
+          // was a sourcemap and it tried to look up the original
+          // location but there was no original URL. This is a strange
+          // scenario so we simply don't pause.
+                      DevToolsUtils.reportException(
+            "ThreadActor",
+            new Error("Attempted to pause in a script with a sourcemap but " +
+                      "could not find original location.")
+          );
+
+                      return undefined;
+                    }
+
+                    packet.frame.where = {
+                      source: originalLocation.originalSourceActor.form(),
+                      line: originalLocation.originalLine,
+                      column: originalLocation.originalColumn
+                    };
+                    resolve(onPacket(packet))
+          .then(null, error => {
+            reportError(error);
+            return {
+              error: "unknownError",
+              message: error.message + "\n" + error.stack
+            };
+          })
+          .then(packet => {
+            this.conn.send(packet);
+          });
+                  });
+
+      this._pushThreadPause();
+    } catch (e) {
+      reportError(e, "Got an exception during TA__pauseAndRespond: ");
+    }
+
+    // If the browser tab has been closed, terminate the debuggee script
+    // instead of continuing. Executing JS after the content window is gone is
+    // a bad idea.
+    return this._tabClosed ? null : undefined;
+  },
+
+  _makeOnEnterFrame: function ({ pauseAndRespond }) {
+    return aFrame => {
+      const generatedLocation = this.sources.getFrameLocation(aFrame);
+      let { originalSourceActor } = this.unsafeSynchronize(this.sources.getOriginalLocation(
+        generatedLocation));
+      let url = originalSourceActor.url;
+
+      return this.sources.isBlackBoxed(url)
+        ? undefined
+        : pauseAndRespond(aFrame);
+    };
+  },
+
+  _makeOnPop: function ({ thread, pauseAndRespond, createValueGrip }) {
+    return function (aCompletion) {
+      // onPop is called with 'this' set to the current frame.
+
+      const generatedLocation = thread.sources.getFrameLocation(this);
+      const { originalSourceActor } = thread.unsafeSynchronize(thread.sources.getOriginalLocation(
+        generatedLocation));
+      const url = originalSourceActor.url;
+
+      if (thread.sources.isBlackBoxed(url)) {
+        return undefined;
+      }
+
+      // Note that we're popping this frame; we need to watch for
+      // subsequent step events on its caller.
+      this.reportedPop = true;
+
+      return pauseAndRespond(this, aPacket => {
+        aPacket.why.frameFinished = {};
+        if (!aCompletion) {
+          aPacket.why.frameFinished.terminated = true;
+        } else if (aCompletion.hasOwnProperty("return")) {
+          aPacket.why.frameFinished.return = createValueGrip(aCompletion.return);
+        } else if (aCompletion.hasOwnProperty("yield")) {
+          aPacket.why.frameFinished.return = createValueGrip(aCompletion.yield);
+        } else {
+          aPacket.why.frameFinished.throw = createValueGrip(aCompletion.throw);
+        }
+        return aPacket;
+      });
+    };
+  },
+
+  _makeOnStep: function ({ thread, pauseAndRespond, startFrame,
+                           startLocation, steppingType }) {
+    // Breaking in place: we should always pause.
+    if (steppingType === "break") {
+      return function () {
+        return pauseAndRespond(this);
+      };
+    }
+
+    // Otherwise take what a "step" means into consideration.
+    return function () {
+      // onStep is called with 'this' set to the current frame.
+
+      // Only allow stepping stops at entry points for the line, when
+      // the stepping occurs in a single frame.  The "same frame"
+      // check makes it so a sequence of steps can step out of a frame
+      // and into subsequent calls in the outer frame.  E.g., if there
+      // is a call "a(b())" and the user steps into b, then this
+      // condition makes it possible to step out of b and into a.
+      if (this === startFrame &&
+          !this.script.getOffsetLocation(this.offset).isEntryPoint) {
+        return undefined;
+      }
+
+      const generatedLocation = thread.sources.getFrameLocation(this);
+      const newLocation = thread.unsafeSynchronize(thread.sources.getOriginalLocation(
+        generatedLocation));
+
+      // Cases when we should pause because we have executed enough to consider
+      // a "step" to have occured:
+      //
+      // 1.1. We change frames.
+      // 1.2. We change URLs (can happen without changing frames thanks to
+      //      source mapping).
+      // 1.3. We change lines.
+      //
+      // Cases when we should always continue execution, even if one of the
+      // above cases is true:
+      //
+      // 2.1. We are in a source mapped region, but inside a null mapping
+      //      (doesn't correlate to any region of original source)
+      // 2.2. The source we are in is black boxed.
+
+      // Cases 2.1 and 2.2
+      if (newLocation.originalUrl == null
+          || thread.sources.isBlackBoxed(newLocation.originalUrl)) {
+        return undefined;
+      }
+
+      // Cases 1.1, 1.2 and 1.3
+      if (this !== startFrame
+          || startLocation.originalUrl !== newLocation.originalUrl
+          || startLocation.originalLine !== newLocation.originalLine) {
+        return pauseAndRespond(this);
+      }
+
+      // Otherwise, let execution continue (we haven't executed enough code to
+      // consider this a "step" yet).
+      return undefined;
+    };
+  },
+
+  /**
+   * Define the JS hook functions for stepping.
+   */
+  _makeSteppingHooks: function (aStartLocation, steppingType) {
+    // Bind these methods and state because some of the hooks are called
+    // with 'this' set to the current frame. Rather than repeating the
+    // binding in each _makeOnX method, just do it once here and pass it
+    // in to each function.
+    const steppingHookState = {
+      pauseAndRespond: (aFrame, onPacket = k=>k) => {
+        return this._pauseAndRespond(aFrame, { type: "resumeLimit" }, onPacket);
+      },
+      createValueGrip: v => createValueGrip(v, this._pausePool,
+        this.objectGrip),
+      thread: this,
+      startFrame: this.youngestFrame,
+      startLocation: aStartLocation,
+      steppingType: steppingType
+    };
+
+    return {
+      onEnterFrame: this._makeOnEnterFrame(steppingHookState),
+      onPop: this._makeOnPop(steppingHookState),
+      onStep: this._makeOnStep(steppingHookState)
+    };
+  },
+
+  /**
+   * Handle attaching the various stepping hooks we need to attach when we
+   * receive a resume request with a resumeLimit property.
+   *
+   * @param Object aRequest
+   *        The request packet received over the RDP.
+   * @returns A promise that resolves to true once the hooks are attached, or is
+   *          rejected with an error packet.
+   */
+  _handleResumeLimit: function (aRequest) {
+    let steppingType = aRequest.resumeLimit.type;
+    if (["break", "step", "next", "finish"].indexOf(steppingType) == -1) {
+      return reject({ error: "badParameterType",
+                      message: "Unknown resumeLimit type" });
+    }
+
+    const generatedLocation = this.sources.getFrameLocation(this.youngestFrame);
+    return this.sources.getOriginalLocation(generatedLocation)
+      .then(originalLocation => {
+        const { onEnterFrame, onPop, onStep } = this._makeSteppingHooks(originalLocation,
+                                                                        steppingType);
+
+        // Make sure there is still a frame on the stack if we are to continue
+        // stepping.
+        let stepFrame = this._getNextStepFrame(this.youngestFrame);
+        if (stepFrame) {
+          switch (steppingType) {
+            case "step":
+              this.dbg.onEnterFrame = onEnterFrame;
+              // Fall through.
+            case "break":
+            case "next":
+              if (stepFrame.script) {
+                stepFrame.onStep = onStep;
+              }
+              stepFrame.onPop = onPop;
+              break;
+            case "finish":
+              stepFrame.onPop = onPop;
+          }
+        }
+
+        return true;
+      });
+  },
+
+  /**
+   * Clear the onStep and onPop hooks from the given frame and all of the frames
+   * below it.
+   *
+   * @param Debugger.Frame aFrame
+   *        The frame we want to clear the stepping hooks from.
+   */
+  _clearSteppingHooks: function (aFrame) {
+    if (aFrame && aFrame.live) {
+      while (aFrame) {
+        aFrame.onStep = undefined;
+        aFrame.onPop = undefined;
+        aFrame = aFrame.older;
+      }
+    }
+  },
+
+  /**
+   * Listen to the debuggee's DOM events if we received a request to do so.
+   *
+   * @param Object aRequest
+   *        The resume request packet received over the RDP.
+   */
+  _maybeListenToEvents: function (aRequest) {
+    // Break-on-DOMEvents is only supported in content debugging.
+    let events = aRequest.pauseOnDOMEvents;
+    if (this.global && events &&
+        (events == "*" ||
+        (Array.isArray(events) && events.length))) {
+      this._pauseOnDOMEvents = events;
+      let els = Cc["@mozilla.org/eventlistenerservice;1"]
+                .getService(Ci.nsIEventListenerService);
+      els.addListenerForAllEvents(this.global, this._allEventsListener, true);
+    }
+  },
+
+  /**
+   * If we are tasked with breaking on the load event, we have to add the
+   * listener early enough.
+   */
+  _onWindowReady: function () {
+    this._maybeListenToEvents({
+      pauseOnDOMEvents: this._pauseOnDOMEvents
+    });
+  },
+
+  /**
+   * Handle a protocol request to resume execution of the debuggee.
+   */
+  onResume: function (aRequest) {
+    if (this._state !== "paused") {
+      return {
+        error: "wrongState",
+        message: "Can't resume when debuggee isn't paused. Current state is '"
+          + this._state + "'",
+        state: this._state
+      };
+    }
+
+    // In case of multiple nested event loops (due to multiple debuggers open in
+    // different tabs or multiple debugger clients connected to the same tab)
+    // only allow resumption in a LIFO order.
+    if (this._nestedEventLoops.size && this._nestedEventLoops.lastPausedUrl
+        && (this._nestedEventLoops.lastPausedUrl !== this._parent.url
+            || this._nestedEventLoops.lastConnection !== this.conn)) {
+      return {
+        error: "wrongOrder",
+        message: "trying to resume in the wrong order.",
+        lastPausedUrl: this._nestedEventLoops.lastPausedUrl
+      };
+    }
+
+    let resumeLimitHandled;
+    if (aRequest && aRequest.resumeLimit) {
+      resumeLimitHandled = this._handleResumeLimit(aRequest);
+    } else {
+      this._clearSteppingHooks(this.youngestFrame);
+      resumeLimitHandled = resolve(true);
+    }
+
+    return resumeLimitHandled.then(() => {
+      if (aRequest) {
+        this._options.pauseOnExceptions = aRequest.pauseOnExceptions;
+        this._options.ignoreCaughtExceptions = aRequest.ignoreCaughtExceptions;
+        this.maybePauseOnExceptions();
+        this._maybeListenToEvents(aRequest);
+      }
+
+      let packet = this._resumed();
+      this._popThreadPause();
+      // Tell anyone who cares of the resume (as of now, that's the xpcshell
+      // harness)
+      if (Services.obs) {
+        Services.obs.notifyObservers(this, "devtools-thread-resumed", null);
+      }
+      return packet;
+    }, error => {
+      return error instanceof Error
+        ? { error: "unknownError",
+            message: DevToolsUtils.safeErrorString(error) }
+        // It is a known error, and the promise was rejected with an error
+        // packet.
+        : error;
+    });
+  },
+
+  /**
+   * Spin up a nested event loop so we can synchronously resolve a promise.
+   *
+   * DON'T USE THIS UNLESS YOU ABSOLUTELY MUST! Nested event loops suck: the
+   * world's state can change out from underneath your feet because JS is no
+   * longer run-to-completion.
+   *
+   * @param aPromise
+   *        The promise we want to resolve.
+   * @returns The promise's resolution.
+   */
+  unsafeSynchronize: function (aPromise) {
+    let needNest = true;
+    let eventLoop;
+    let returnVal;
+
+    aPromise
+      .then((aResolvedVal) => {
+        needNest = false;
+        returnVal = aResolvedVal;
+      })
+      .then(null, (aError) => {
+        reportError(aError, "Error inside unsafeSynchronize:");
+      })
+      .then(() => {
+        if (eventLoop) {
+          eventLoop.resolve();
+        }
+      });
+
+    if (needNest) {
+      eventLoop = this._nestedEventLoops.push();
+      eventLoop.enter();
+    }
+
+    return returnVal;
+  },
+
+  /**
+   * Set the debugging hook to pause on exceptions if configured to do so.
+   */
+  maybePauseOnExceptions: function () {
+    if (this._options.pauseOnExceptions) {
+      this.dbg.onExceptionUnwind = this.onExceptionUnwind.bind(this);
+    }
+  },
+
+  /**
+   * A listener that gets called for every event fired on the page, when a list
+   * of interesting events was provided with the pauseOnDOMEvents property. It
+   * is used to set server-managed breakpoints on any existing event listeners
+   * for those events.
+   *
+   * @param Event event
+   *        The event that was fired.
+   */
+  _allEventsListener: function (event) {
+    if (this._pauseOnDOMEvents == "*" ||
+        this._pauseOnDOMEvents.indexOf(event.type) != -1) {
+      for (let listener of this._getAllEventListeners(event.target)) {
+        if (event.type == listener.type || this._pauseOnDOMEvents == "*") {
+          this._breakOnEnter(listener.script);
+        }
+      }
+    }
+  },
+
+  /**
+   * Return an array containing all the event listeners attached to the
+   * specified event target and its ancestors in the event target chain.
+   *
+   * @param EventTarget eventTarget
+   *        The target the event was dispatched on.
+   * @returns Array
+   */
+  _getAllEventListeners: function (eventTarget) {
+    let els = Cc["@mozilla.org/eventlistenerservice;1"]
+                .getService(Ci.nsIEventListenerService);
+
+    let targets = els.getEventTargetChainFor(eventTarget, true);
+    let listeners = [];
+
+    for (let target of targets) {
+      let handlers = els.getListenerInfoFor(target);
+      for (let handler of handlers) {
+        // Null is returned for all-events handlers, and native event listeners
+        // don't provide any listenerObject, which makes them not that useful to
+        // a JS debugger.
+        if (!handler || !handler.listenerObject || !handler.type)
+          continue;
+        // Create a listener-like object suitable for our purposes.
+        let l = Object.create(null);
+        l.type = handler.type;
+        let listener = handler.listenerObject;
+        let listenerDO = this.globalDebugObject.makeDebuggeeValue(listener);
+        // If the listener is not callable, assume it is an event handler object.
+        if (!listenerDO.callable) {
+          // For some events we don't have permission to access the
+          // 'handleEvent' property when running in content scope.
+          if (!listenerDO.unwrap()) {
+            continue;
+          }
+          let heDesc;
+          while (!heDesc && listenerDO) {
+            heDesc = listenerDO.getOwnPropertyDescriptor("handleEvent");
+            listenerDO = listenerDO.proto;
+          }
+          if (heDesc && heDesc.value) {
+            listenerDO = heDesc.value;
+          }
+        }
+        // When the listener is a bound function, we are actually interested in
+        // the target function.
+        while (listenerDO.isBoundFunction) {
+          listenerDO = listenerDO.boundTargetFunction;
+        }
+        l.script = listenerDO.script;
+        // Chrome listeners won't be converted to debuggee values, since their
+        // compartment is not added as a debuggee.
+        if (!l.script)
+          continue;
+        listeners.push(l);
+      }
+    }
+    return listeners;
+  },
+
+  /**
+   * Set a breakpoint on the first line of the given script that has an entry
+   * point.
+   */
+  _breakOnEnter: function (script) {
+    let offsets = script.getAllOffsets();
+    for (let line = 0, n = offsets.length; line < n; line++) {
+      if (offsets[line]) {
+        // N.B. Hidden breakpoints do not have an original location, and are not
+        // stored in the breakpoint actor map.
+        let actor = new BreakpointActor(this);
+        this.threadLifetimePool.addActor(actor);
+
+        let scripts = this.dbg.findScripts({ source: script.source, line: line });
+        let entryPoints = findEntryPointsForLine(scripts, line);
+        setBreakpointAtEntryPoints(actor, entryPoints);
+        this._hiddenBreakpoints.set(actor.actorID, actor);
+        break;
+      }
+    }
+  },
+
+  /**
+   * Helper method that returns the next frame when stepping.
+   */
+  _getNextStepFrame: function (aFrame) {
+    let stepFrame = aFrame.reportedPop ? aFrame.older : aFrame;
+    if (!stepFrame || !stepFrame.script) {
+      stepFrame = null;
+    }
+    return stepFrame;
+  },
+
+  onClientEvaluate: function (aRequest) {
+    if (this.state !== "paused") {
+      return { error: "wrongState",
+               message: "Debuggee must be paused to evaluate code." };
+    }
+
+    let frame = this._requestFrame(aRequest.frame);
+    if (!frame) {
+      return { error: "unknownFrame",
+               message: "Evaluation frame not found" };
+    }
+
+    if (!frame.environment) {
+      return { error: "notDebuggee",
+               message: "cannot access the environment of this frame." };
+    }
+
+    let youngest = this.youngestFrame;
+
+    // Put ourselves back in the running state and inform the client.
+    let resumedPacket = this._resumed();
+    this.conn.send(resumedPacket);
+
+    // Run the expression.
+    // XXX: test syntax errors
+    let completion = frame.eval(aRequest.expression);
+
+    // Put ourselves back in the pause state.
+    let packet = this._paused(youngest);
+    packet.why = { type: "clientEvaluated",
+                   frameFinished: this.createProtocolCompletionValue(completion) };
+
+    // Return back to our previous pause's event loop.
+    return packet;
+  },
+
+  onFrames: function (aRequest) {
+    if (this.state !== "paused") {
+      return { error: "wrongState",
+               message: "Stack frames are only available while the debuggee is paused."};
+    }
+
+    let start = aRequest.start ? aRequest.start : 0;
+    let count = aRequest.count;
+
+    // Find the starting frame...
+    let frame = this.youngestFrame;
+    let i = 0;
+    while (frame && (i < start)) {
+      frame = frame.older;
+      i++;
+    }
+
+    // Return request.count frames, or all remaining
+    // frames if count is not defined.
+    let promises = [];
+    for (; frame && (!count || i < (start + count)); i++, frame = frame.older) {
+      let form = this._createFrameActor(frame).form();
+      form.depth = i;
+
+      let promise = this.sources.getOriginalLocation(new GeneratedLocation(
+        this.sources.createNonSourceMappedActor(frame.script.source),
+        form.where.line,
+        form.where.column
+      )).then((originalLocation) => {
+        if (!originalLocation.originalSourceActor) {
+          return null;
+        }
+
+        let sourceForm = originalLocation.originalSourceActor.form();
+        form.where = {
+          source: sourceForm,
+          line: originalLocation.originalLine,
+          column: originalLocation.originalColumn
+        };
+        form.source = sourceForm;
+        return form;
+      });
+      promises.push(promise);
+    }
+
+    return all(promises).then(function (frames) {
+      // Filter null values because sourcemapping may have failed.
+      return { frames: frames.filter(x => !!x) };
+    });
+  },
+
+  onReleaseMany: function (aRequest) {
+    if (!aRequest.actors) {
+      return { error: "missingParameter",
+               message: "no actors were specified" };
+    }
+
+    let res;
+    for (let actorID of aRequest.actors) {
+      let actor = this.threadLifetimePool.get(actorID);
+      if (!actor) {
+        if (!res) {
+          res = { error: "notReleasable",
+                  message: "Only thread-lifetime actors can be released." };
+        }
+        continue;
+      }
+      actor.onRelease();
+    }
+    return res ? res : {};
+  },
+
+  /**
+   * Get the script and source lists from the debugger.
+   */
+  _discoverSources: function () {
+    // Only get one script per Debugger.Source.
+    const sourcesToScripts = new Map();
+    const scripts = this.dbg.findScripts();
+
+    for (let i = 0, len = scripts.length; i < len; i++) {
+      let s = scripts[i];
+      if (s.source) {
+        sourcesToScripts.set(s.source, s);
+      }
+    }
+
+    return all([...sourcesToScripts.values()].map(script => {
+      return this.sources.createSourceActors(script.source);
+    }));
+  },
+
+  onSources: function (aRequest) {
+    return this._discoverSources().then(() => {
+      // No need to flush the new source packets here, as we are sending the
+      // list of sources out immediately and we don't need to invoke the
+      // overhead of an RDP packet for every source right now. Let the default
+      // timeout flush the buffered packets.
+
+      return {
+        sources: this.sources.iter().map(s => s.form())
+      };
+    });
+  },
+
+  /**
+   * Disassociate all breakpoint actors from their scripts and clear the
+   * breakpoint handlers. This method can be used when the thread actor intends
+   * to keep the breakpoint store, but needs to clear any actual breakpoints,
+   * e.g. due to a page navigation. This way the breakpoint actors' script
+   * caches won't hold on to the Debugger.Script objects leaking memory.
+   */
+  disableAllBreakpoints: function () {
+    for (let bpActor of this.breakpointActorMap.findActors()) {
+      bpActor.removeScripts();
+    }
+  },
+
+
+  /**
+   * Handle a protocol request to pause the debuggee.
+   */
+  onInterrupt: function (aRequest) {
+    if (this.state == "exited") {
+      return { type: "exited" };
+    } else if (this.state == "paused") {
+      // TODO: return the actual reason for the existing pause.
+      return { type: "paused", why: { type: "alreadyPaused" } };
+    } else if (this.state != "running") {
+      return { error: "wrongState",
+               message: "Received interrupt request in " + this.state +
+                        " state." };
+    }
+
+    try {
+      // If execution should pause just before the next JavaScript bytecode is
+      // executed, just set an onEnterFrame handler.
+      if (aRequest.when == "onNext") {
+        let onEnterFrame = (aFrame) => {
+          return this._pauseAndRespond(aFrame, { type: "interrupted", onNext: true });
+        };
+        this.dbg.onEnterFrame = onEnterFrame;
+
+        return { type: "willInterrupt" };
+      }
+
+      // If execution should pause immediately, just put ourselves in the paused
+      // state.
+      let packet = this._paused();
+      if (!packet) {
+        return { error: "notInterrupted" };
+      }
+      packet.why = { type: "interrupted" };
+
+      // Send the response to the interrupt request now (rather than
+      // returning it), because we're going to start a nested event loop
+      // here.
+      this.conn.send(packet);
+
+      // Start a nested event loop.
+      this._pushThreadPause();
+
+      // We already sent a response to this request, don't send one
+      // now.
+      return null;
+    } catch (e) {
+      reportError(e);
+      return { error: "notInterrupted", message: e.toString() };
+    }
+  },
+
+  /**
+   * Handle a protocol request to retrieve all the event listeners on the page.
+   */
+  onEventListeners: function (aRequest) {
+    // This request is only supported in content debugging.
+    if (!this.global) {
+      return {
+        error: "notImplemented",
+        message: "eventListeners request is only supported in content debugging"
+      };
+    }
+
+    let els = Cc["@mozilla.org/eventlistenerservice;1"]
+                .getService(Ci.nsIEventListenerService);
+
+    let nodes = this.global.document.getElementsByTagName("*");
+    nodes = [this.global].concat([].slice.call(nodes));
+    let listeners = [];
+
+    for (let node of nodes) {
+      let handlers = els.getListenerInfoFor(node);
+
+      for (let handler of handlers) {
+        // Create a form object for serializing the listener via the protocol.
+        let listenerForm = Object.create(null);
+        let listener = handler.listenerObject;
+        // Native event listeners don't provide any listenerObject or type and
+        // are not that useful to a JS debugger.
+        if (!listener || !handler.type) {
+          continue;
+        }
+
+        // There will be no tagName if the event listener is set on the window.
+        let selector = node.tagName ? CssLogic.findCssSelector(node) : "window";
+        let nodeDO = this.globalDebugObject.makeDebuggeeValue(node);
+        listenerForm.node = {
+          selector: selector,
+          object: createValueGrip(nodeDO, this._pausePool, this.objectGrip)
+        };
+        listenerForm.type = handler.type;
+        listenerForm.capturing = handler.capturing;
+        listenerForm.allowsUntrusted = handler.allowsUntrusted;
+        listenerForm.inSystemEventGroup = handler.inSystemEventGroup;
+        let handlerName = "on" + listenerForm.type;
+        listenerForm.isEventHandler = false;
+        if (typeof node.hasAttribute !== "undefined") {
+          listenerForm.isEventHandler = !!node.hasAttribute(handlerName);
+        }
+        if (!!node[handlerName]) {
+          listenerForm.isEventHandler = !!node[handlerName];
+        }
+        // Get the Debugger.Object for the listener object.
+        let listenerDO = this.globalDebugObject.makeDebuggeeValue(listener);
+        // If the listener is an object with a 'handleEvent' method, use that.
+        if (listenerDO.class == "Object" || listenerDO.class == "XULElement") {
+          // For some events we don't have permission to access the
+          // 'handleEvent' property when running in content scope.
+          if (!listenerDO.unwrap()) {
+            continue;
+          }
+          let heDesc;
+          while (!heDesc && listenerDO) {
+            heDesc = listenerDO.getOwnPropertyDescriptor("handleEvent");
+            listenerDO = listenerDO.proto;
+          }
+          if (heDesc && heDesc.value) {
+            listenerDO = heDesc.value;
+          }
+        }
+        // When the listener is a bound function, we are actually interested in
+        // the target function.
+        while (listenerDO.isBoundFunction) {
+          listenerDO = listenerDO.boundTargetFunction;
+        }
+        listenerForm.function = createValueGrip(listenerDO, this._pausePool,
+          this.objectGrip);
+        listeners.push(listenerForm);
+      }
+    }
+    return { listeners: listeners };
+  },
+
+  /**
+   * Return the Debug.Frame for a frame mentioned by the protocol.
+   */
+  _requestFrame: function (aFrameID) {
+    if (!aFrameID) {
+      return this.youngestFrame;
+    }
+
+    if (this._framePool.has(aFrameID)) {
+      return this._framePool.get(aFrameID).frame;
+    }
+
+    return undefined;
+  },
+
+  _paused: function (aFrame) {
+    // We don't handle nested pauses correctly.  Don't try - if we're
+    // paused, just continue running whatever code triggered the pause.
+    // We don't want to actually have nested pauses (although we
+    // have nested event loops).  If code runs in the debuggee during
+    // a pause, it should cause the actor to resume (dropping
+    // pause-lifetime actors etc) and then repause when complete.
+
+    if (this.state === "paused") {
+      return undefined;
+    }
+
+    // Clear stepping hooks.
+    this.dbg.onEnterFrame = undefined;
+    this.dbg.onExceptionUnwind = undefined;
+    if (aFrame) {
+      aFrame.onStep = undefined;
+      aFrame.onPop = undefined;
+    }
+
+    // Clear DOM event breakpoints.
+    // XPCShell tests don't use actual DOM windows for globals and cause
+    // removeListenerForAllEvents to throw.
+    if (!isWorker && this.global && !this.global.toString().includes("Sandbox")) {
+      let els = Cc["@mozilla.org/eventlistenerservice;1"]
+                .getService(Ci.nsIEventListenerService);
+      els.removeListenerForAllEvents(this.global, this._allEventsListener, true);
+      for (let [, bp] of this._hiddenBreakpoints) {
+        bp.delete();
+      }
+      this._hiddenBreakpoints.clear();
+    }
+
+    this._state = "paused";
+
+    // Create the actor pool that will hold the pause actor and its
+    // children.
+    assert(!this._pausePool, "No pause pool should exist yet");
+    this._pausePool = new ActorPool(this.conn);
+    this.conn.addActorPool(this._pausePool);
+
+    // Give children of the pause pool a quick link back to the
+    // thread...
+    this._pausePool.threadActor = this;
+
+    // Create the pause actor itself...
+    assert(!this._pauseActor, "No pause actor should exist yet");
+    this._pauseActor = new PauseActor(this._pausePool);
+    this._pausePool.addActor(this._pauseActor);
+
+    // Update the list of frames.
+    let poppedFrames = this._updateFrames();
+
+    // Send off the paused packet and spin an event loop.
+    let packet = { from: this.actorID,
+                   type: "paused",
+                   actor: this._pauseActor.actorID };
+    if (aFrame) {
+      packet.frame = this._createFrameActor(aFrame).form();
+    }
+
+    if (poppedFrames) {
+      packet.poppedFrames = poppedFrames;
+    }
+
+    return packet;
+  },
+
+  _resumed: function () {
+    this._state = "running";
+
+    // Drop the actors in the pause actor pool.
+    this.conn.removeActorPool(this._pausePool);
+
+    this._pausePool = null;
+    this._pauseActor = null;
+
+    return { from: this.actorID, type: "resumed" };
+  },
+
+  /**
+   * Expire frame actors for frames that have been popped.
+   *
+   * @returns A list of actor IDs whose frames have been popped.
+   */
+  _updateFrames: function () {
+    let popped = [];
+
+    // Create the actor pool that will hold the still-living frames.
+    let framePool = new ActorPool(this.conn);
+    let frameList = [];
+
+    for (let frameActor of this._frameActors) {
+      if (frameActor.frame.live) {
+        framePool.addActor(frameActor);
+        frameList.push(frameActor);
+      } else {
+        popped.push(frameActor.actorID);
+      }
+    }
+
+    // Remove the old frame actor pool, this will expire
+    // any actors that weren't added to the new pool.
+    if (this._framePool) {
+      this.conn.removeActorPool(this._framePool);
+    }
+
+    this._frameActors = frameList;
+    this._framePool = framePool;
+    this.conn.addActorPool(framePool);
+
+    return popped;
+  },
+
+  _createFrameActor: function (aFrame) {
+    if (aFrame.actor) {
+      return aFrame.actor;
+    }
+
+    let actor = new FrameActor(aFrame, this);
+    this._frameActors.push(actor);
+    this._framePool.addActor(actor);
+    aFrame.actor = actor;
+
+    return actor;
+  },
+
+  /**
+   * Create and return an environment actor that corresponds to the provided
+   * Debugger.Environment.
+   * @param Debugger.Environment aEnvironment
+   *        The lexical environment we want to extract.
+   * @param object aPool
+   *        The pool where the newly-created actor will be placed.
+   * @return The EnvironmentActor for aEnvironment or undefined for host
+   *         functions or functions scoped to a non-debuggee global.
+   */
+  createEnvironmentActor: function (aEnvironment, aPool) {
+    if (!aEnvironment) {
+      return undefined;
+    }
+
+    if (aEnvironment.actor) {
+      return aEnvironment.actor;
+    }
+
+    let actor = new EnvironmentActor(aEnvironment, this);
+    aPool.addActor(actor);
+    aEnvironment.actor = actor;
+
+    return actor;
+  },
+
+  /**
+   * Return a protocol completion value representing the given
+   * Debugger-provided completion value.
+   */
+  createProtocolCompletionValue: function (aCompletion) {
+    let protoValue = {};
+    if (aCompletion == null) {
+      protoValue.terminated = true;
+    } else if ("return" in aCompletion) {
+      protoValue.return = createValueGrip(aCompletion.return,
+        this._pausePool, this.objectGrip);
+    } else if ("throw" in aCompletion) {
+      protoValue.throw = createValueGrip(aCompletion.throw,
+        this._pausePool, this.objectGrip);
+    } else {
+      protoValue.return = createValueGrip(aCompletion.yield,
+        this._pausePool, this.objectGrip);
+    }
+    return protoValue;
+  },
+
+  /**
+   * Create a grip for the given debuggee object.
+   *
+   * @param aValue Debugger.Object
+   *        The debuggee object value.
+   * @param aPool ActorPool
+   *        The actor pool where the new object actor will be added.
+   */
+  objectGrip: function (aValue, aPool) {
+    if (!aPool.objectActors) {
+      aPool.objectActors = new WeakMap();
+    }
+
+    if (aPool.objectActors.has(aValue)) {
+      return aPool.objectActors.get(aValue).grip();
+    } else if (this.threadLifetimePool.objectActors.has(aValue)) {
+      return this.threadLifetimePool.objectActors.get(aValue).grip();
+    }
+
+    let actor = new PauseScopedObjectActor(aValue, {
+      getGripDepth: () => this._gripDepth,
+      incrementGripDepth: () => this._gripDepth++,
+      decrementGripDepth: () => this._gripDepth--,
+      createValueGrip: v => createValueGrip(v, this._pausePool,
+        this.pauseObjectGrip),
+      sources: () => this.sources,
+      createEnvironmentActor: (env, pool) =>
+        this.createEnvironmentActor(env, pool),
+      promote: () => this.threadObjectGrip(actor),
+      isThreadLifetimePool: () =>
+        actor.registeredPool !== this.threadLifetimePool,
+      getGlobalDebugObject: () => this.globalDebugObject
+    });
+    aPool.addActor(actor);
+    aPool.objectActors.set(aValue, actor);
+    return actor.grip();
+  },
+
+  /**
+   * Create a grip for the given debuggee object with a pause lifetime.
+   *
+   * @param aValue Debugger.Object
+   *        The debuggee object value.
+   */
+  pauseObjectGrip: function (aValue) {
+    if (!this._pausePool) {
+      throw "Object grip requested while not paused.";
+    }
+
+    return this.objectGrip(aValue, this._pausePool);
+  },
+
+  /**
+   * Extend the lifetime of the provided object actor to thread lifetime.
+   *
+   * @param aActor object
+   *        The object actor.
+   */
+  threadObjectGrip: function (aActor) {
+    // We want to reuse the existing actor ID, so we just remove it from the
+    // current pool's weak map and then let pool.addActor do the rest.
+    aActor.registeredPool.objectActors.delete(aActor.obj);
+    this.threadLifetimePool.addActor(aActor);
+    this.threadLifetimePool.objectActors.set(aActor.obj, aActor);
+  },
+
+  /**
+   * Handle a protocol request to promote multiple pause-lifetime grips to
+   * thread-lifetime grips.
+   *
+   * @param aRequest object
+   *        The protocol request object.
+   */
+  onThreadGrips: function (aRequest) {
+    if (this.state != "paused") {
+      return { error: "wrongState" };
+    }
+
+    if (!aRequest.actors) {
+      return { error: "missingParameter",
+               message: "no actors were specified" };
+    }
+
+    for (let actorID of aRequest.actors) {
+      let actor = this._pausePool.get(actorID);
+      if (actor) {
+        this.threadObjectGrip(actor);
+      }
+    }
+    return {};
+  },
+
+  /**
+   * Create a long string grip that is scoped to a pause.
+   *
+   * @param aString String
+   *        The string we are creating a grip for.
+   */
+  pauseLongStringGrip: function (aString) {
+    return longStringGrip(aString, this._pausePool);
+  },
+
+  /**
+   * Create a long string grip that is scoped to a thread.
+   *
+   * @param aString String
+   *        The string we are creating a grip for.
+   */
+  threadLongStringGrip: function (aString) {
+    return longStringGrip(aString, this._threadLifetimePool);
+  },
+
+  // JS Debugger API hooks.
+
+  /**
+   * A function that the engine calls when a call to a debug event hook,
+   * breakpoint handler, watchpoint handler, or similar function throws some
+   * exception.
+   *
+   * @param aException exception
+   *        The exception that was thrown in the debugger code.
+   */
+  uncaughtExceptionHook: function (aException) {
+    dumpn("Got an exception: " + aException.message + "\n" + aException.stack);
+  },
+
+  /**
+   * A function that the engine calls when a debugger statement has been
+   * executed in the specified frame.
+   *
+   * @param aFrame Debugger.Frame
+   *        The stack frame that contained the debugger statement.
+   */
+  onDebuggerStatement: function (aFrame) {
+    // Don't pause if we are currently stepping (in or over) or the frame is
+    // black-boxed.
+    const generatedLocation = this.sources.getFrameLocation(aFrame);
+    const { originalSourceActor } = this.unsafeSynchronize(this.sources.getOriginalLocation(
+      generatedLocation));
+    const url = originalSourceActor ? originalSourceActor.url : null;
+
+    return this.sources.isBlackBoxed(url) || aFrame.onStep
+      ? undefined
+      : this._pauseAndRespond(aFrame, { type: "debuggerStatement" });
+  },
+
+  /**
+   * A function that the engine calls when an exception has been thrown and has
+   * propagated to the specified frame.
+   *
+   * @param aFrame Debugger.Frame
+   *        The youngest remaining stack frame.
+   * @param aValue object
+   *        The exception that was thrown.
+   */
+  onExceptionUnwind: function (aFrame, aValue) {
+    let willBeCaught = false;
+    for (let frame = aFrame; frame != null; frame = frame.older) {
+      if (frame.script.isInCatchScope(frame.offset)) {
+        willBeCaught = true;
+        break;
+      }
+    }
+
+    if (willBeCaught && this._options.ignoreCaughtExceptions) {
+      return undefined;
+    }
+
+    // NS_ERROR_NO_INTERFACE exceptions are a special case in browser code,
+    // since they're almost always thrown by QueryInterface functions, and
+    // handled cleanly by native code.
+    if (aValue == Cr.NS_ERROR_NO_INTERFACE) {
+      return undefined;
+    }
+
+    const generatedLocation = this.sources.getFrameLocation(aFrame);
+    const { originalSourceActor } = this.unsafeSynchronize(this.sources.getOriginalLocation(
+      generatedLocation));
+    const url = originalSourceActor ? originalSourceActor.url : null;
+
+    if (this.sources.isBlackBoxed(url)) {
+      return undefined;
+    }
+
+    try {
+      let packet = this._paused(aFrame);
+      if (!packet) {
+        return undefined;
+      }
+
+      packet.why = { type: "exception",
+                     exception: createValueGrip(aValue, this._pausePool,
+                                                this.objectGrip)
+                   };
+      this.conn.send(packet);
+
+      this._pushThreadPause();
+    } catch (e) {
+      reportError(e, "Got an exception during TA_onExceptionUnwind: ");
+    }
+
+    return undefined;
+  },
+
+  /**
+   * A function that the engine calls when a new script has been loaded into the
+   * scope of the specified debuggee global.
+   *
+   * @param aScript Debugger.Script
+   *        The source script that has been loaded into a debuggee compartment.
+   * @param aGlobal Debugger.Object
+   *        A Debugger.Object instance whose referent is the global object.
+   */
+  onNewScript: function (aScript, aGlobal) {
+    this._addSource(aScript.source);
+  },
+
+  /**
+   * A function called when there's a new or updated source from a thread actor's
+   * sources. Emits `newSource` and `updatedSource` on the tab actor.
+   *
+   * @param {String} name
+   * @param {SourceActor} source
+   */
+  onSourceEvent: function (name, source) {
+    this.conn.send({
+      from: this._parent.actorID,
+      type: name,
+      source: source.form()
+    });
+
+    // For compatibility and debugger still using `newSource` on the thread client,
+    // still emit this event here. Clean up in bug 1247084
+    if (name === "newSource") {
+      this.conn.send({
+        from: this.actorID,
+        type: name,
+        source: source.form()
+      });
+    }
+  },
+
+  /**
+   * Add the provided source to the server cache.
+   *
+   * @param aSource Debugger.Source
+   *        The source that will be stored.
+   * @returns true, if the source was added; false otherwise.
+   */
+  _addSource: function (aSource) {
+    if (!this.sources.allowSource(aSource) || this._debuggerSourcesSeen.has(aSource)) {
+      return false;
+    }
+
+    let sourceActor = this.sources.createNonSourceMappedActor(aSource);
+    let bpActors = [...this.breakpointActorMap.findActors()];
+
+    if (this._options.useSourceMaps) {
+      let promises = [];
+
+      // Go ahead and establish the source actors for this script, which
+      // fetches sourcemaps if available and sends onNewSource
+      // notifications.
+      let sourceActorsCreated = this.sources._createSourceMappedActors(aSource);
+
+      if (bpActors.length) {
+        // We need to use unsafeSynchronize here because if the page is being reloaded,
+        // this call will replace the previous set of source actors for this source
+        // with a new one. If the source actors have not been replaced by the time
+        // we try to reset the breakpoints below, their location objects will still
+        // point to the old set of source actors, which point to different
+        // scripts.
+        this.unsafeSynchronize(sourceActorsCreated);
+      }
+
+      for (let _actor of bpActors) {
+        // XXX bug 1142115: We do async work in here, so we need to create a fresh
+        // binding because for/of does not yet do that in SpiderMonkey.
+        let actor = _actor;
+
+        if (actor.isPending) {
+          promises.push(actor.originalLocation.originalSourceActor._setBreakpoint(actor));
+        } else {
+          promises.push(this.sources.getAllGeneratedLocations(actor.originalLocation)
+                                    .then((generatedLocations) => {
+            if (generatedLocations.length > 0 &&
+                generatedLocations[0].generatedSourceActor.actorID === sourceActor.actorID) {
+              sourceActor._setBreakpointAtAllGeneratedLocations(actor, generatedLocations);
+            }
+          }));
+        }
+      }
+
+      if (promises.length > 0) {
+        this.unsafeSynchronize(promise.all(promises));
+      }
+    } else {
+      // Bug 1225160: If addSource is called in response to a new script
+      // notification, and this notification was triggered by loading a JSM from
+      // chrome code, calling unsafeSynchronize could cause a debuggee timer to
+      // fire. If this causes the JSM to be loaded a second time, the browser
+      // will crash, because loading JSMS is not reentrant, and the first load
+      // has not completed yet.
+      //
+      // The root of the problem is that unsafeSynchronize can cause debuggee
+      // code to run. Unfortunately, fixing that is prohibitively difficult. The
+      // best we can do at the moment is disable source maps for the browser
+      // debugger, and carefully avoid the use of unsafeSynchronize in this
+      // function when source maps are disabled.
+      for (let actor of bpActors) {
+        if (actor.isPending) {
+          actor.originalLocation.originalSourceActor._setBreakpoint(actor);
+        } else {
+          actor.originalLocation.originalSourceActor._setBreakpointAtGeneratedLocation(
+            actor, GeneratedLocation.fromOriginalLocation(actor.originalLocation)
+          );
+        }
+      }
+    }
+
+    this._debuggerSourcesSeen.add(aSource);
+    return true;
+  },
+
+
+  /**
+   * Get prototypes and properties of multiple objects.
+   */
+  onPrototypesAndProperties: function (aRequest) {
+    let result = {};
+    for (let actorID of aRequest.actors) {
+      // This code assumes that there are no lazily loaded actors returned
+      // by this call.
+      let actor = this.conn.getActor(actorID);
+      if (!actor) {
+        return { from: this.actorID,
+                 error: "noSuchActor" };
+      }
+      let handler = actor.onPrototypeAndProperties;
+      if (!handler) {
+        return { from: this.actorID,
+                 error: "unrecognizedPacketType",
+                 message: ('Actor "' + actorID +
+                           '" does not recognize the packet type ' +
+                           '"prototypeAndProperties"') };
+      }
+      result[actorID] = handler.call(actor, {});
+    }
+    return { from: this.actorID,
+             actors: result };
+  }
+});
+
+ThreadActor.prototype.requestTypes = object.merge(ThreadActor.prototype.requestTypes, {
+  "attach": ThreadActor.prototype.onAttach,
+  "detach": ThreadActor.prototype.onDetach,
+  "reconfigure": ThreadActor.prototype.onReconfigure,
+  "resume": ThreadActor.prototype.onResume,
+  "clientEvaluate": ThreadActor.prototype.onClientEvaluate,
+  "frames": ThreadActor.prototype.onFrames,
+  "interrupt": ThreadActor.prototype.onInterrupt,
+  "eventListeners": ThreadActor.prototype.onEventListeners,
+  "releaseMany": ThreadActor.prototype.onReleaseMany,
+  "sources": ThreadActor.prototype.onSources,
+  "threadGrips": ThreadActor.prototype.onThreadGrips,
+  "prototypesAndProperties": ThreadActor.prototype.onPrototypesAndProperties
+});
+
+exports.ThreadActor = ThreadActor;
+
+/**
+ * Creates a PauseActor.
+ *
+ * PauseActors exist for the lifetime of a given debuggee pause.  Used to
+ * scope pause-lifetime grips.
+ *
+ * @param ActorPool aPool
+ *        The actor pool created for this pause.
+ */
+function PauseActor(aPool)
+{
+  this.pool = aPool;
+}
+
+PauseActor.prototype = {
+  actorPrefix: "pause"
+};
+
+
+/**
+ * A base actor for any actors that should only respond receive messages in the
+ * paused state. Subclasses may expose a `threadActor` which is used to help
+ * determine when we are in a paused state. Subclasses should set their own
+ * "constructor" property if they want better error messages. You should never
+ * instantiate a PauseScopedActor directly, only through subclasses.
+ */
+function PauseScopedActor()
+{
+}
+
+/**
+ * A function decorator for creating methods to handle protocol messages that
+ * should only be received while in the paused state.
+ *
+ * @param aMethod Function
+ *        The function we are decorating.
+ */
+PauseScopedActor.withPaused = function (aMethod) {
+  return function () {
+    if (this.isPaused()) {
+      return aMethod.apply(this, arguments);
+    } else {
+      return this._wrongState();
+    }
+  };
+};
+
+PauseScopedActor.prototype = {
+
+  /**
+   * Returns true if we are in the paused state.
+   */
+  isPaused: function () {
+    // When there is not a ThreadActor available (like in the webconsole) we
+    // have to be optimistic and assume that we are paused so that we can
+    // respond to requests.
+    return this.threadActor ? this.threadActor.state === "paused" : true;
+  },
+
+  /**
+   * Returns the wrongState response packet for this actor.
+   */
+  _wrongState: function () {
+    return {
+      error: "wrongState",
+      message: this.constructor.name +
+        " actors can only be accessed while the thread is paused."
+    };
+  }
+};
+
+/**
+ * Creates a pause-scoped actor for the specified object.
+ * @see ObjectActor
+ */
+function PauseScopedObjectActor(obj, hooks) {
+  ObjectActor.call(this, obj, hooks);
+  this.hooks.promote = hooks.promote;
+  this.hooks.isThreadLifetimePool = hooks.isThreadLifetimePool;
+}
+
+PauseScopedObjectActor.prototype = Object.create(PauseScopedActor.prototype);
+
+Object.assign(PauseScopedObjectActor.prototype, ObjectActor.prototype);
+
+Object.assign(PauseScopedObjectActor.prototype, {
+  constructor: PauseScopedObjectActor,
+  actorPrefix: "pausedobj",
+
+  onOwnPropertyNames:
+    PauseScopedActor.withPaused(ObjectActor.prototype.onOwnPropertyNames),
+
+  onPrototypeAndProperties:
+    PauseScopedActor.withPaused(ObjectActor.prototype.onPrototypeAndProperties),
+
+  onPrototype: PauseScopedActor.withPaused(ObjectActor.prototype.onPrototype),
+  onProperty: PauseScopedActor.withPaused(ObjectActor.prototype.onProperty),
+  onDecompile: PauseScopedActor.withPaused(ObjectActor.prototype.onDecompile),
+
+  onDisplayString:
+    PauseScopedActor.withPaused(ObjectActor.prototype.onDisplayString),
+
+  onParameterNames:
+    PauseScopedActor.withPaused(ObjectActor.prototype.onParameterNames),
+
+  /**
+   * Handle a protocol request to promote a pause-lifetime grip to a
+   * thread-lifetime grip.
+   *
+   * @param aRequest object
+   *        The protocol request object.
+   */
+  onThreadGrip: PauseScopedActor.withPaused(function (aRequest) {
+    this.hooks.promote();
+    return {};
+  }),
+
+  /**
+   * Handle a protocol request to release a thread-lifetime grip.
+   *
+   * @param aRequest object
+   *        The protocol request object.
+   */
+  onRelease: PauseScopedActor.withPaused(function (aRequest) {
+    if (this.hooks.isThreadLifetimePool()) {
+      return { error: "notReleasable",
+               message: "Only thread-lifetime actors can be released." };
+    }
+
+    this.release();
+    return {};
+  }),
+});
+
+Object.assign(PauseScopedObjectActor.prototype.requestTypes, {
+  "threadGrip": PauseScopedObjectActor.prototype.onThreadGrip,
+});
+
+function hackDebugger(Debugger) {
+  // TODO: Improve native code instead of hacking on top of it
+
+  /**
+   * Override the toString method in order to get more meaningful script output
+   * for debugging the debugger.
+   */
+  Debugger.Script.prototype.toString = function () {
+    let output = "";
+    if (this.url) {
+      output += this.url;
+    }
+    if (typeof this.staticLevel != "undefined") {
+      output += ":L" + this.staticLevel;
+    }
+    if (typeof this.startLine != "undefined") {
+      output += ":" + this.startLine;
+      if (this.lineCount && this.lineCount > 1) {
+        output += "-" + (this.startLine + this.lineCount - 1);
+      }
+    }
+    if (typeof this.startLine != "undefined") {
+      output += ":" + this.startLine;
+      if (this.lineCount && this.lineCount > 1) {
+        output += "-" + (this.startLine + this.lineCount - 1);
+      }
+    }
+    if (this.strictMode) {
+      output += ":strict";
+    }
+    return output;
+  };
+
+  /**
+   * Helper property for quickly getting to the line number a stack frame is
+   * currently paused at.
+   */
+  Object.defineProperty(Debugger.Frame.prototype, "line", {
+    configurable: true,
+    get: function () {
+      if (this.script) {
+        return this.script.getOffsetLocation(this.offset).lineNumber;
+      } else {
+        return null;
+      }
+    }
+  });
+}
+
+
+/**
+ * Creates an actor for handling chrome debugging. ChromeDebuggerActor is a
+ * thin wrapper over ThreadActor, slightly changing some of its behavior.
+ *
+ * @param aConnection object
+ *        The DebuggerServerConnection with which this ChromeDebuggerActor
+ *        is associated. (Currently unused, but required to make this
+ *        constructor usable with addGlobalActor.)
+ *
+ * @param aParent object
+ *        This actor's parent actor. See ThreadActor for a list of expected
+ *        properties.
+ */
+function ChromeDebuggerActor(aConnection, aParent)
+{
+  ThreadActor.prototype.initialize.call(this, aParent);
+}
+
+ChromeDebuggerActor.prototype = Object.create(ThreadActor.prototype);
+
+Object.assign(ChromeDebuggerActor.prototype, {
+  constructor: ChromeDebuggerActor,
+
+  // A constant prefix that will be used to form the actor ID by the server.
+  actorPrefix: "chromeDebugger"
+});
+
+exports.ChromeDebuggerActor = ChromeDebuggerActor;
+
+/**
+ * Creates an actor for handling add-on debugging. AddonThreadActor is
+ * a thin wrapper over ThreadActor.
+ *
+ * @param aConnection object
+ *        The DebuggerServerConnection with which this AddonThreadActor
+ *        is associated. (Currently unused, but required to make this
+ *        constructor usable with addGlobalActor.)
+ *
+ * @param aParent object
+ *        This actor's parent actor. See ThreadActor for a list of expected
+ *        properties.
+ */
+function AddonThreadActor(aConnect, aParent) {
+  ThreadActor.prototype.initialize.call(this, aParent);
+}
+
+AddonThreadActor.prototype = Object.create(ThreadActor.prototype);
+
+Object.assign(AddonThreadActor.prototype, {
+  constructor: AddonThreadActor,
+
+  // A constant prefix that will be used to form the actor ID by the server.
+  actorPrefix: "addonThread"
+});
+
+exports.AddonThreadActor = AddonThreadActor;
+
+// Utility functions.
+
+/**
+ * Report the given error in the error console and to stdout.
+ *
+ * @param Error aError
+ *        The error object you wish to report.
+ * @param String aPrefix
+ *        An optional prefix for the reported error message.
+ */
+var oldReportError = reportError;
+reportError = function (aError, aPrefix = "") {
+  assert(aError instanceof Error, "Must pass Error objects to reportError");
+  let msg = aPrefix + aError.message + ":\n" + aError.stack;
+  oldReportError(msg);
+  dumpn(msg);
+};
+
+/**
+ * Find the scripts which contain offsets that are an entry point to the given
+ * line.
+ *
+ * @param Array scripts
+ *        The set of Debugger.Scripts to consider.
+ * @param Number line
+ *        The line we are searching for entry points into.
+ * @returns Array of objects of the form { script, offsets } where:
+ *          - script is a Debugger.Script
+ *          - offsets is an array of offsets that are entry points into the
+ *            given line.
+ */
+function findEntryPointsForLine(scripts, line) {
+  const entryPoints = [];
+  for (let script of scripts) {
+    const offsets = script.getLineOffsets(line);
+    if (offsets.length) {
+      entryPoints.push({ script, offsets });
+    }
+  }
+  return entryPoints;
+}
+
+/**
+ * Unwrap a global that is wrapped in a |Debugger.Object|, or if the global has
+ * become a dead object, return |undefined|.
+ *
+ * @param Debugger.Object wrappedGlobal
+ *        The |Debugger.Object| which wraps a global.
+ *
+ * @returns {Object|undefined}
+ *          Returns the unwrapped global object or |undefined| if unwrapping
+ *          failed.
+ */
+exports.unwrapDebuggerObjectGlobal = wrappedGlobal => {
+  try {
+    // Because of bug 991399 we sometimes get nuked window references here. We
+    // just bail out in that case.
+    //
+    // Note that addon sandboxes have a DOMWindow as their prototype. So make
+    // sure that we can touch the prototype too (whatever it is), in case _it_
+    // is it a nuked window reference. We force stringification to make sure
+    // that any dead object proxies make themselves known.
+    let global = wrappedGlobal.unsafeDereference();
+    Object.getPrototypeOf(global) + "";
+    return global;
+  }
+  catch (e) {
+    return undefined;
+  }
+};
diff --git a/devtools/server/actors/settings.js b/devtools/server/actors/settings.js
new file mode 100644
index 000000000..179c82aa5
--- /dev/null
+++ b/devtools/server/actors/settings.js
@@ -0,0 +1,146 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {Cc, Ci} = require("chrome");
+const protocol = require("devtools/shared/protocol");
+const {DebuggerServer} = require("devtools/server/main");
+const promise = require("promise");
+const Services = require("Services");
+const { settingsSpec } = require("devtools/shared/specs/settings");
+const { FileUtils} = require("resource://gre/modules/FileUtils.jsm");
+const { NetUtil} = require("resource://gre/modules/NetUtil.jsm");
+
+var defaultSettings = {};
+var settingsFile;
+
+exports.register = function (handle) {
+  handle.addGlobalActor(SettingsActor, "settingsActor");
+};
+
+exports.unregister = function (handle) {
+};
+
+function getDefaultSettings() {
+  let chan = NetUtil.newChannel({
+    uri: NetUtil.newURI(settingsFile),
+    loadUsingSystemPrincipal: true});
+  let stream = chan.open2();
+  // Obtain a converter to read from a UTF-8 encoded input stream.
+  let converter = Cc["@mozilla.org/intl/scriptableunicodeconverter"]
+                  .createInstance(Ci.nsIScriptableUnicodeConverter);
+  converter.charset = "UTF-8";
+  let rawstr = converter.ConvertToUnicode(NetUtil.readInputStreamToString(
+                                          stream,
+                                          stream.available()) || "");
+
+  try {
+    defaultSettings = JSON.parse(rawstr);
+  } catch (e) { }
+  stream.close();
+}
+
+function loadSettingsFile() {
+  // Loading resource://app/defaults/settings.json doesn't work because
+  // settings.json is not in the omnijar.
+  // So we look for the app dir instead and go from here...
+  if (settingsFile) {
+    return;
+  }
+  settingsFile = FileUtils.getFile("DefRt", ["settings.json"], false);
+  if (!settingsFile || (settingsFile && !settingsFile.exists())) {
+    // On b2g desktop builds the settings.json file is moved in the
+    // profile directory by the build system.
+    settingsFile = FileUtils.getFile("ProfD", ["settings.json"], false);
+    if (!settingsFile || (settingsFile && !settingsFile.exists())) {
+      console.log("settings.json file does not exist");
+    }
+  }
+
+  if (settingsFile.exists()) {
+    getDefaultSettings();
+  }
+}
+
+var SettingsActor = exports.SettingsActor = protocol.ActorClassWithSpec(settingsSpec, {
+  _getSettingsService: function () {
+    let win = Services.wm.getMostRecentWindow(DebuggerServer.chromeWindowType);
+    return win.navigator.mozSettings;
+  },
+
+  getSetting: function (name) {
+    let deferred = promise.defer();
+    let lock = this._getSettingsService().createLock();
+    let req = lock.get(name);
+    req.onsuccess = function () {
+      deferred.resolve(req.result[name]);
+    };
+    req.onerror = function () {
+      deferred.reject(req.error);
+    };
+    return deferred.promise;
+  },
+
+  setSetting: function (name, value) {
+    let deferred = promise.defer();
+    let data = {};
+    data[name] = value;
+    let lock = this._getSettingsService().createLock();
+    let req = lock.set(data);
+    req.onsuccess = function () {
+      deferred.resolve(true);
+    };
+    req.onerror = function () {
+      deferred.reject(req.error);
+    };
+    return deferred.promise;
+  },
+
+  _hasUserSetting: function (name, value) {
+    if (typeof value === "object") {
+      return JSON.stringify(defaultSettings[name]) !== JSON.stringify(value);
+    }
+    return (defaultSettings[name] !== value);
+  },
+
+  getAllSettings: function () {
+    loadSettingsFile();
+    let settings = {};
+    let self = this;
+
+    let deferred = promise.defer();
+    let lock = this._getSettingsService().createLock();
+    let req = lock.get("*");
+
+    req.onsuccess = function () {
+      for (var name in req.result) {
+        settings[name] = {
+          value: req.result[name],
+          hasUserValue: self._hasUserSetting(name, req.result[name])
+        };
+      }
+      deferred.resolve(settings);
+    };
+    req.onfailure = function () {
+      deferred.reject(req.error);
+    };
+
+    return deferred.promise;
+  },
+
+  clearUserSetting: function (name) {
+    loadSettingsFile();
+    try {
+      this.setSetting(name, defaultSettings[name]);
+    } catch (e) {
+      console.log(e);
+    }
+  }
+});
+
+// For tests
+exports._setDefaultSettings = function (settings) {
+  defaultSettings = settings || {};
+};
diff --git a/devtools/server/actors/source.js b/devtools/server/actors/source.js
new file mode 100644
index 000000000..e76c14fe8
--- /dev/null
+++ b/devtools/server/actors/source.js
@@ -0,0 +1,902 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cc, Ci } = require("chrome");
+const Services = require("Services");
+const { BreakpointActor, setBreakpointAtEntryPoints } = require("devtools/server/actors/breakpoint");
+const { OriginalLocation, GeneratedLocation } = require("devtools/server/actors/common");
+const { createValueGrip } = require("devtools/server/actors/object");
+const { ActorClassWithSpec, Arg, RetVal, method } = require("devtools/shared/protocol");
+const DevToolsUtils = require("devtools/shared/DevToolsUtils");
+const { assert, fetch } = DevToolsUtils;
+const { joinURI } = require("devtools/shared/path");
+const promise = require("promise");
+const { defer, resolve, reject, all } = promise;
+const { sourceSpec } = require("devtools/shared/specs/source");
+
+loader.lazyRequireGetter(this, "SourceMapConsumer", "source-map", true);
+loader.lazyRequireGetter(this, "SourceMapGenerator", "source-map", true);
+loader.lazyRequireGetter(this, "mapURIToAddonID", "devtools/server/actors/utils/map-uri-to-addon-id");
+
+function isEvalSource(source) {
+  let introType = source.introductionType;
+  // These are all the sources that are essentially eval-ed (either
+  // by calling eval or passing a string to one of these functions).
+  return (introType === "eval" ||
+          introType === "Function" ||
+          introType === "eventHandler" ||
+          introType === "setTimeout" ||
+          introType === "setInterval");
+}
+
+exports.isEvalSource = isEvalSource;
+
+function getSourceURL(source, window) {
+  if (isEvalSource(source)) {
+    // Eval sources have no urls, but they might have a `displayURL`
+    // created with the sourceURL pragma. If the introduction script
+    // is a non-eval script, generate an full absolute URL relative to it.
+
+    if (source.displayURL && source.introductionScript &&
+       !isEvalSource(source.introductionScript.source)) {
+
+      if (source.introductionScript.source.url === "debugger eval code") {
+        if (window) {
+          // If this is a named eval script created from the console, make it
+          // relative to the current page. window is only available
+          // when we care about this.
+          return joinURI(window.location.href, source.displayURL);
+        }
+      }
+      else {
+        return joinURI(source.introductionScript.source.url, source.displayURL);
+      }
+    }
+
+    return source.displayURL;
+  }
+  else if (source.url === "debugger eval code") {
+    // Treat code evaluated by the console as unnamed eval scripts
+    return null;
+  }
+  return source.url;
+}
+
+exports.getSourceURL = getSourceURL;
+
+/**
+ * Resolve a URI back to physical file.
+ *
+ * Of course, this works only for URIs pointing to local resources.
+ *
+ * @param  aURI
+ *         URI to resolve
+ * @return
+ *         resolved nsIURI
+ */
+function resolveURIToLocalPath(aURI) {
+  let resolved;
+  switch (aURI.scheme) {
+    case "jar":
+    case "file":
+      return aURI;
+
+    case "chrome":
+      resolved = Cc["@mozilla.org/chrome/chrome-registry;1"].
+                 getService(Ci.nsIChromeRegistry).convertChromeURL(aURI);
+      return resolveURIToLocalPath(resolved);
+
+    case "resource":
+      resolved = Cc["@mozilla.org/network/protocol;1?name=resource"].
+                 getService(Ci.nsIResProtocolHandler).resolveURI(aURI);
+      aURI = Services.io.newURI(resolved, null, null);
+      return resolveURIToLocalPath(aURI);
+
+    default:
+      return null;
+  }
+}
+
+/**
+ * A SourceActor provides information about the source of a script. There
+ * are two kinds of source actors: ones that represent real source objects,
+ * and ones that represent non-existant "original" sources when the real
+ * sources are sourcemapped. When a source is sourcemapped, actors are
+ * created for both the "generated" and "original" sources, and the client will
+ * only see the original sources. We separate these because there isn't
+ * a 1:1 mapping of generated to original sources; one generated source
+ * may represent N original sources, so we need to create N + 1 separate
+ * actors.
+ *
+ * There are 4 different scenarios for sources that you should
+ * understand:
+ *
+ * - A single non-sourcemapped source that is not inlined in HTML
+ *   (separate JS file, eval'ed code, etc)
+ * - A single sourcemapped source which creates N original sources
+ * - An HTML page with multiple inline scripts, which are distinct
+ *   sources, but should be represented as a single source
+ * - A pretty-printed source (which may or may not be an original
+ *   sourcemapped source), which generates a sourcemap for itself
+ *
+ * The complexity of `SourceActor` and `ThreadSources` are to handle
+ * all of thise cases and hopefully internalize the complexities.
+ *
+ * @param Debugger.Source source
+ *        The source object we are representing.
+ * @param ThreadActor thread
+ *        The current thread actor.
+ * @param String originalUrl
+ *        Optional. For sourcemapped urls, the original url this is representing.
+ * @param Debugger.Source generatedSource
+ *        Optional, passed in when aSourceMap is also passed in. The generated
+ *        source object that introduced this source.
+ * @param Boolean isInlineSource
+ *        Optional. True if this is an inline source from a HTML or XUL page.
+ * @param String contentType
+ *        Optional. The content type of this source, if immediately available.
+ */
+let SourceActor = ActorClassWithSpec(sourceSpec, {
+  typeName: "source",
+
+  initialize: function ({ source, thread, originalUrl, generatedSource,
+                          isInlineSource, contentType }) {
+    this._threadActor = thread;
+    this._originalUrl = originalUrl;
+    this._source = source;
+    this._generatedSource = generatedSource;
+    this._contentType = contentType;
+    this._isInlineSource = isInlineSource;
+
+    this.onSource = this.onSource.bind(this);
+    this._invertSourceMap = this._invertSourceMap.bind(this);
+    this._encodeAndSetSourceMapURL = this._encodeAndSetSourceMapURL.bind(this);
+    this._getSourceText = this._getSourceText.bind(this);
+
+    this._mapSourceToAddon();
+
+    if (this.threadActor.sources.isPrettyPrinted(this.url)) {
+      this._init = this.prettyPrint(
+        this.threadActor.sources.prettyPrintIndent(this.url)
+      ).then(null, error => {
+        DevToolsUtils.reportException("SourceActor", error);
+      });
+    } else {
+      this._init = null;
+    }
+  },
+
+  get isSourceMapped() {
+    return !!(!this.isInlineSource && (
+      this._originalURL || this._generatedSource ||
+        this.threadActor.sources.isPrettyPrinted(this.url)
+    ));
+  },
+
+  get isInlineSource() {
+    return this._isInlineSource;
+  },
+
+  get threadActor() { return this._threadActor; },
+  get sources() { return this._threadActor.sources; },
+  get dbg() { return this.threadActor.dbg; },
+  get source() { return this._source; },
+  get generatedSource() { return this._generatedSource; },
+  get breakpointActorMap() { return this.threadActor.breakpointActorMap; },
+  get url() {
+    if (this.source) {
+      return getSourceURL(this.source, this.threadActor._parent.window);
+    }
+    return this._originalUrl;
+  },
+  get addonID() { return this._addonID; },
+  get addonPath() { return this._addonPath; },
+
+  get prettyPrintWorker() {
+    return this.threadActor.prettyPrintWorker;
+  },
+
+  form: function () {
+    let source = this.source || this.generatedSource;
+    // This might not have a source or a generatedSource because we
+    // treat HTML pages with inline scripts as a special SourceActor
+    // that doesn't have either
+    let introductionUrl = null;
+    if (source && source.introductionScript) {
+      introductionUrl = source.introductionScript.source.url;
+    }
+
+    return {
+      actor: this.actorID,
+      generatedUrl: this.generatedSource ? this.generatedSource.url : null,
+      url: this.url ? this.url.split(" -> ").pop() : null,
+      addonID: this._addonID,
+      addonPath: this._addonPath,
+      isBlackBoxed: this.threadActor.sources.isBlackBoxed(this.url),
+      isPrettyPrinted: this.threadActor.sources.isPrettyPrinted(this.url),
+      isSourceMapped: this.isSourceMapped,
+      sourceMapURL: source ? source.sourceMapURL : null,
+      introductionUrl: introductionUrl ? introductionUrl.split(" -> ").pop() : null,
+      introductionType: source ? source.introductionType : null
+    };
+  },
+
+  disconnect: function () {
+    if (this.registeredPool && this.registeredPool.sourceActors) {
+      delete this.registeredPool.sourceActors[this.actorID];
+    }
+  },
+
+  _mapSourceToAddon: function () {
+    try {
+      var nsuri = Services.io.newURI(this.url.split(" -> ").pop(), null, null);
+    }
+    catch (e) {
+      // We can't do anything with an invalid URI
+      return;
+    }
+
+    let localURI = resolveURIToLocalPath(nsuri);
+    if (!localURI) {
+      return;
+    }
+
+    let id = mapURIToAddonID(localURI);
+    if (!id) {
+      return;
+    }
+    this._addonID = id;
+
+    if (localURI instanceof Ci.nsIJARURI) {
+      // The path in the add-on is easy for jar: uris
+      this._addonPath = localURI.JAREntry;
+    }
+    else if (localURI instanceof Ci.nsIFileURL) {
+      // For file: uris walk up to find the last directory that is part of the
+      // add-on
+      let target = localURI.file;
+      let path = target.leafName;
+
+      // We can assume that the directory containing the source file is part
+      // of the add-on
+      let root = target.parent;
+      let file = root.parent;
+      while (file && mapURIToAddonID(Services.io.newFileURI(file))) {
+        path = root.leafName + "/" + path;
+        root = file;
+        file = file.parent;
+      }
+
+      if (!file) {
+        const error = new Error("Could not find the root of the add-on for " + this.url);
+        DevToolsUtils.reportException("SourceActor.prototype._mapSourceToAddon", error);
+        return;
+      }
+
+      this._addonPath = path;
+    }
+  },
+
+  _reportLoadSourceError: function (error, map = null) {
+    try {
+      DevToolsUtils.reportException("SourceActor", error);
+
+      JSON.stringify(this.form(), null, 4).split(/\n/g)
+        .forEach(line => console.error("\t", line));
+
+      if (!map) {
+        return;
+      }
+
+      console.error("\t", "source map's sourceRoot =", map.sourceRoot);
+
+      console.error("\t", "source map's sources =");
+      map.sources.forEach(s => {
+        let hasSourceContent = map.sourceContentFor(s, true);
+        console.error("\t\t", s, "\t",
+                      hasSourceContent ? "has source content" : "no source content");
+      });
+
+      console.error("\t", "source map's sourcesContent =");
+      map.sourcesContent.forEach(c => {
+        if (c.length > 80) {
+          c = c.slice(0, 77) + "...";
+        }
+        c = c.replace(/\n/g, "\\n");
+        console.error("\t\t", c);
+      });
+    } catch (e) { }
+  },
+
+  _getSourceText: function () {
+    let toResolvedContent = t => ({
+      content: t,
+      contentType: this._contentType
+    });
+
+    let genSource = this.generatedSource || this.source;
+    return this.threadActor.sources.fetchSourceMap(genSource).then(map => {
+      if (map) {
+        try {
+          let sourceContent = map.sourceContentFor(this.url);
+          if (sourceContent) {
+            return toResolvedContent(sourceContent);
+          }
+        } catch (error) {
+          this._reportLoadSourceError(error, map);
+          throw error;
+        }
+      }
+
+      // Use `source.text` if it exists, is not the "no source" string, and
+      // the content type of the source is JavaScript or it is synthesized
+      // wasm. It will be "no source" if the Debugger API wasn't able to load
+      // the source because sources were discarded
+      // (javascript.options.discardSystemSource == true). Re-fetch non-JS
+      // sources to get the contentType from the headers.
+      if (this.source &&
+          this.source.text !== "[no source]" &&
+          this._contentType &&
+          (this._contentType.indexOf("javascript") !== -1 ||
+           this._contentType === "text/wasm")) {
+        return toResolvedContent(this.source.text);
+      }
+      else {
+        // Only load the HTML page source from cache (which exists when
+        // there are inline sources). Otherwise, we can't trust the
+        // cache because we are most likely here because we are
+        // fetching the original text for sourcemapped code, and the
+        // page hasn't requested it before (if it has, it was a
+        // previous debugging session).
+        let loadFromCache = this.isInlineSource;
+
+        // Fetch the sources with the same principal as the original document
+        let win = this.threadActor._parent.window;
+        let principal, cacheKey;
+        // On xpcshell, we don't have a window but a Sandbox
+        if (!isWorker && win instanceof Ci.nsIDOMWindow) {
+          let webNav = win.QueryInterface(Ci.nsIInterfaceRequestor)
+                          .getInterface(Ci.nsIWebNavigation);
+          let channel = webNav.currentDocumentChannel;
+          principal = channel.loadInfo.loadingPrincipal;
+
+          // Retrieve the cacheKey in order to load POST requests from cache
+          // Note that chrome:// URLs don't support this interface.
+          if (loadFromCache &&
+            webNav.currentDocumentChannel instanceof Ci.nsICacheInfoChannel) {
+            cacheKey = webNav.currentDocumentChannel.cacheKey;
+            assert(
+              cacheKey,
+              "Could not fetch the cacheKey from the related document."
+            );
+          }
+        }
+
+        let sourceFetched = fetch(this.url, {
+          principal,
+          cacheKey,
+          loadFromCache
+        });
+
+        // Record the contentType we just learned during fetching
+        return sourceFetched
+          .then(result => {
+            this._contentType = result.contentType;
+            return result;
+          }, error => {
+            this._reportLoadSourceError(error, map);
+            throw error;
+          });
+      }
+    });
+  },
+
+  /**
+   * Get all executable lines from the current source
+   * @return Array - Executable lines of the current script
+   **/
+  getExecutableLines: function () {
+    function sortLines(lines) {
+      // Converting the Set into an array
+      lines = [...lines];
+      lines.sort((a, b) => {
+        return a - b;
+      });
+      return lines;
+    }
+
+    if (this.generatedSource) {
+      return this.threadActor.sources.getSourceMap(this.generatedSource).then(sm => {
+        let lines = new Set();
+
+        // Position of executable lines in the generated source
+        let offsets = this.getExecutableOffsets(this.generatedSource, false);
+        for (let offset of offsets) {
+          let {line, source: sourceUrl} = sm.originalPositionFor({
+            line: offset.lineNumber,
+            column: offset.columnNumber
+          });
+
+          if (sourceUrl === this.url) {
+            lines.add(line);
+          }
+        }
+
+        return sortLines(lines);
+      });
+    }
+
+    let lines = this.getExecutableOffsets(this.source, true);
+    return sortLines(lines);
+  },
+
+  /**
+   * Extract all executable offsets from the given script
+   * @param String url - extract offsets of the script with this url
+   * @param Boolean onlyLine - will return only the line number
+   * @return Set - Executable offsets/lines of the script
+   **/
+  getExecutableOffsets: function (source, onlyLine) {
+    let offsets = new Set();
+    for (let s of this.dbg.findScripts({ source })) {
+      for (let offset of s.getAllColumnOffsets()) {
+        offsets.add(onlyLine ? offset.lineNumber : offset);
+      }
+    }
+
+    return offsets;
+  },
+
+  /**
+   * Handler for the "source" packet.
+   */
+  onSource: function () {
+    return resolve(this._init)
+      .then(this._getSourceText)
+      .then(({ content, contentType }) => {
+        return {
+          source: createValueGrip(content, this.threadActor.threadLifetimePool,
+            this.threadActor.objectGrip),
+          contentType: contentType
+        };
+      })
+      .then(null, aError => {
+        reportError(aError, "Got an exception during SA_onSource: ");
+        throw new Error("Could not load the source for " + this.url + ".\n" +
+                        DevToolsUtils.safeErrorString(aError));
+      });
+  },
+
+  /**
+   * Handler for the "prettyPrint" packet.
+   */
+  prettyPrint: function (indent) {
+    this.threadActor.sources.prettyPrint(this.url, indent);
+    return this._getSourceText()
+      .then(this._sendToPrettyPrintWorker(indent))
+      .then(this._invertSourceMap)
+      .then(this._encodeAndSetSourceMapURL)
+      .then(() => {
+        // We need to reset `_init` now because we have already done the work of
+        // pretty printing, and don't want onSource to wait forever for
+        // initialization to complete.
+        this._init = null;
+      })
+      .then(this.onSource)
+      .then(null, error => {
+        this.disablePrettyPrint();
+        throw new Error(DevToolsUtils.safeErrorString(error));
+      });
+  },
+
+  /**
+   * Return a function that sends a request to the pretty print worker, waits on
+   * the worker's response, and then returns the pretty printed code.
+   *
+   * @param Number aIndent
+   *        The number of spaces to indent by the code by, when we send the
+   *        request to the pretty print worker.
+   * @returns Function
+   *          Returns a function which takes an AST, and returns a promise that
+   *          is resolved with `{ code, mappings }` where `code` is the pretty
+   *          printed code, and `mappings` is an array of source mappings.
+   */
+  _sendToPrettyPrintWorker: function (aIndent) {
+    return ({ content }) => {
+      return this.prettyPrintWorker.performTask("pretty-print", {
+        url: this.url,
+        indent: aIndent,
+        source: content
+      });
+    };
+  },
+
+  /**
+   * Invert a source map. So if a source map maps from a to b, return a new
+   * source map from b to a. We need to do this because the source map we get
+   * from _generatePrettyCodeAndMap goes the opposite way we want it to for
+   * debugging.
+   *
+   * Note that the source map is modified in place.
+   */
+  _invertSourceMap: function ({ code, mappings }) {
+    const generator = new SourceMapGenerator({ file: this.url });
+    return DevToolsUtils.yieldingEach(mappings._array, m => {
+      let mapping = {
+        generated: {
+          line: m.originalLine,
+          column: m.originalColumn
+        }
+      };
+      if (m.source) {
+        mapping.source = m.source;
+        mapping.original = {
+          line: m.generatedLine,
+          column: m.generatedColumn
+        };
+        mapping.name = m.name;
+      }
+      generator.addMapping(mapping);
+    }).then(() => {
+      generator.setSourceContent(this.url, code);
+      let consumer = SourceMapConsumer.fromSourceMap(generator);
+
+      return {
+        code: code,
+        map: consumer
+      };
+    });
+  },
+
+  /**
+   * Save the source map back to our thread's ThreadSources object so that
+   * stepping, breakpoints, debugger statements, etc can use it. If we are
+   * pretty printing a source mapped source, we need to compose the existing
+   * source map with our new one.
+   */
+  _encodeAndSetSourceMapURL: function ({ map: sm }) {
+    let source = this.generatedSource || this.source;
+    let sources = this.threadActor.sources;
+
+    return sources.getSourceMap(source).then(prevMap => {
+      if (prevMap) {
+        // Compose the source maps
+        this._oldSourceMapping = {
+          url: source.sourceMapURL,
+          map: prevMap
+        };
+
+        prevMap = SourceMapGenerator.fromSourceMap(prevMap);
+        prevMap.applySourceMap(sm, this.url);
+        sm = SourceMapConsumer.fromSourceMap(prevMap);
+      }
+
+      let sources = this.threadActor.sources;
+      sources.clearSourceMapCache(source.sourceMapURL);
+      sources.setSourceMapHard(source, null, sm);
+    });
+  },
+
+  /**
+   * Handler for the "disablePrettyPrint" packet.
+   */
+  disablePrettyPrint: function () {
+    let source = this.generatedSource || this.source;
+    let sources = this.threadActor.sources;
+    let sm = sources.getSourceMap(source);
+
+    sources.clearSourceMapCache(source.sourceMapURL, { hard: true });
+
+    if (this._oldSourceMapping) {
+      sources.setSourceMapHard(source,
+                               this._oldSourceMapping.url,
+                               this._oldSourceMapping.map);
+      this._oldSourceMapping = null;
+    }
+
+    this.threadActor.sources.disablePrettyPrint(this.url);
+    return this.onSource();
+  },
+
+  /**
+   * Handler for the "blackbox" packet.
+   */
+  blackbox: function () {
+    this.threadActor.sources.blackBox(this.url);
+    if (this.threadActor.state == "paused"
+        && this.threadActor.youngestFrame
+        && this.threadActor.youngestFrame.script.url == this.url) {
+      return true;
+    }
+    return false;
+  },
+
+  /**
+   * Handler for the "unblackbox" packet.
+   */
+  unblackbox: function () {
+    this.threadActor.sources.unblackBox(this.url);
+  },
+
+  /**
+   * Handle a request to set a breakpoint.
+   *
+   * @param Number line
+   *        Line to break on.
+   * @param Number column
+   *        Column to break on.
+   * @param String condition
+   *        A condition which must be true for breakpoint to be hit.
+   * @param Boolean noSliding
+   *        If true, disables breakpoint sliding.
+   *
+   * @returns Promise
+   *          A promise that resolves to a JSON object representing the
+   *          response.
+   */
+  setBreakpoint: function (line, column, condition, noSliding) {
+    if (this.threadActor.state !== "paused") {
+      throw {
+        error: "wrongState",
+        message: "Cannot set breakpoint while debuggee is running."
+      };
+    }
+
+    let location = new OriginalLocation(this, line, column);
+    return this._getOrCreateBreakpointActor(
+      location,
+      condition,
+      noSliding
+    ).then((actor) => {
+      let response = {
+        actor: actor.actorID,
+        isPending: actor.isPending
+      };
+
+      let actualLocation = actor.originalLocation;
+      if (!actualLocation.equals(location)) {
+        response.actualLocation = actualLocation.toJSON();
+      }
+
+      return response;
+    });
+  },
+
+  /**
+   * Get or create a BreakpointActor for the given location in the original
+   * source, and ensure it is set as a breakpoint handler on all scripts that
+   * match the given location.
+   *
+   * @param OriginalLocation originalLocation
+   *        An OriginalLocation representing the location of the breakpoint in
+   *        the original source.
+   * @param String condition
+   *        A string that is evaluated whenever the breakpoint is hit. If the
+   *        string evaluates to false, the breakpoint is ignored.
+   * @param Boolean noSliding
+   *        If true, disables breakpoint sliding.
+   *
+   * @returns BreakpointActor
+   *          A BreakpointActor representing the breakpoint.
+   */
+  _getOrCreateBreakpointActor: function (originalLocation, condition, noSliding) {
+    let actor = this.breakpointActorMap.getActor(originalLocation);
+    if (!actor) {
+      actor = new BreakpointActor(this.threadActor, originalLocation);
+      this.threadActor.threadLifetimePool.addActor(actor);
+      this.breakpointActorMap.setActor(originalLocation, actor);
+    }
+
+    actor.condition = condition;
+
+    return this._setBreakpoint(actor, noSliding);
+  },
+
+  /*
+   * Ensure the given BreakpointActor is set as a breakpoint handler on all
+   * scripts that match its location in the original source.
+   *
+   * If there are no scripts that match the location of the BreakpointActor,
+   * we slide its location to the next closest line (for line breakpoints) or
+   * column (for column breakpoint) that does.
+   *
+   * If breakpoint sliding fails, then either there are no scripts that contain
+   * any code for the given location, or they were all garbage collected before
+   * the debugger started running. We cannot distinguish between these two
+   * cases, so we insert the BreakpointActor in the BreakpointActorMap as
+   * a pending breakpoint. Whenever a new script is introduced, this method is
+   * called again for each pending breakpoint.
+   *
+   * @param BreakpointActor actor
+   *        The BreakpointActor to be set as a breakpoint handler.
+   * @param Boolean noSliding
+   *        If true, disables breakpoint sliding.
+   *
+   * @returns A Promise that resolves to the given BreakpointActor.
+   */
+  _setBreakpoint: function (actor, noSliding) {
+    const { originalLocation } = actor;
+    const { originalLine, originalSourceActor } = originalLocation;
+
+    if (!this.isSourceMapped) {
+      const generatedLocation = GeneratedLocation.fromOriginalLocation(originalLocation);
+      if (!this._setBreakpointAtGeneratedLocation(actor, generatedLocation) &&
+          !noSliding) {
+        const query = { line: originalLine };
+        // For most cases, we have a real source to query for. The
+        // only time we don't is for HTML pages. In that case we want
+        // to query for scripts in an HTML page based on its URL, as
+        // there could be several sources within an HTML page.
+        if (this.source) {
+          query.source = this.source;
+        } else {
+          query.url = this.url;
+        }
+        const scripts = this.dbg.findScripts(query);
+
+        // Never do breakpoint sliding for column breakpoints.
+        // Additionally, never do breakpoint sliding if no scripts
+        // exist on this line.
+        //
+        // Sliding can go horribly wrong if we always try to find the
+        // next line with valid entry points in the entire file.
+        // Scripts may be completely GCed and we never knew they
+        // existed, so we end up sliding through whole functions to
+        // the user's bewilderment.
+        //
+        // We can slide reliably if any scripts exist, however, due
+        // to how scripts are kept alive. A parent Debugger.Script
+        // keeps all of its children alive, so as long as we have a
+        // valid script, we can slide through it and know we won't
+        // slide through any of its child scripts. Additionally, if a
+        // script gets GCed, that means that all parents scripts are
+        // GCed as well, and no scripts will exist on those lines
+        // anymore. We will never slide through a GCed script.
+        if (originalLocation.originalColumn || scripts.length === 0) {
+          return promise.resolve(actor);
+        }
+
+        // Find the script that spans the largest amount of code to
+        // determine the bounds for sliding.
+        const largestScript = scripts.reduce((largestScript, script) => {
+          if (script.lineCount > largestScript.lineCount) {
+            return script;
+          }
+          return largestScript;
+        });
+        const maxLine = largestScript.startLine + largestScript.lineCount - 1;
+
+        let actualLine = originalLine;
+        for (; actualLine <= maxLine; actualLine++) {
+          const loc = new GeneratedLocation(this, actualLine);
+          if (this._setBreakpointAtGeneratedLocation(actor, loc)) {
+            break;
+          }
+        }
+
+        // The above loop should never complete. We only did breakpoint sliding
+        // because we found scripts on the line we started from,
+        // which means there must be valid entry points somewhere
+        // within those scripts.
+        assert(
+          actualLine <= maxLine,
+          "Could not find any entry points to set a breakpoint on, " +
+          "even though I was told a script existed on the line I started " +
+          "the search with."
+        );
+
+        // Update the actor to use the new location (reusing a
+        // previous breakpoint if it already exists on that line).
+        const actualLocation = new OriginalLocation(originalSourceActor, actualLine);
+        const existingActor = this.breakpointActorMap.getActor(actualLocation);
+        this.breakpointActorMap.deleteActor(originalLocation);
+        if (existingActor) {
+          actor.delete();
+          actor = existingActor;
+        } else {
+          actor.originalLocation = actualLocation;
+          this.breakpointActorMap.setActor(actualLocation, actor);
+        }
+      }
+
+      return promise.resolve(actor);
+    } else {
+      return this.sources.getAllGeneratedLocations(originalLocation).then((generatedLocations) => {
+        this._setBreakpointAtAllGeneratedLocations(
+          actor,
+          generatedLocations
+        );
+
+        return actor;
+      });
+    }
+  },
+
+  _setBreakpointAtAllGeneratedLocations: function (actor, generatedLocations) {
+    let success = false;
+    for (let generatedLocation of generatedLocations) {
+      if (this._setBreakpointAtGeneratedLocation(
+        actor,
+        generatedLocation
+      )) {
+        success = true;
+      }
+    }
+    return success;
+  },
+
+  /*
+   * Ensure the given BreakpointActor is set as breakpoint handler on all
+   * scripts that match the given location in the generated source.
+   *
+   * @param BreakpointActor actor
+   *        The BreakpointActor to be set as a breakpoint handler.
+   * @param GeneratedLocation generatedLocation
+   *        A GeneratedLocation representing the location in the generated
+   *        source for which the given BreakpointActor is to be set as a
+   *        breakpoint handler.
+   *
+   * @returns A Boolean that is true if the BreakpointActor was set as a
+   *          breakpoint handler on at least one script, and false otherwise.
+   */
+  _setBreakpointAtGeneratedLocation: function (actor, generatedLocation) {
+    let {
+      generatedSourceActor,
+      generatedLine,
+      generatedColumn,
+      generatedLastColumn
+    } = generatedLocation;
+
+    // Find all scripts that match the given source actor and line
+    // number.
+    const query = { line: generatedLine };
+    if (generatedSourceActor.source) {
+      query.source = generatedSourceActor.source;
+    } else {
+      query.url = generatedSourceActor.url;
+    }
+    let scripts = this.dbg.findScripts(query);
+
+    scripts = scripts.filter((script) => !actor.hasScript(script));
+
+    // Find all entry points that correspond to the given location.
+    let entryPoints = [];
+    if (generatedColumn === undefined) {
+      // This is a line breakpoint, so we are interested in all offsets
+      // that correspond to the given line number.
+      for (let script of scripts) {
+        let offsets = script.getLineOffsets(generatedLine);
+        if (offsets.length > 0) {
+          entryPoints.push({ script, offsets });
+        }
+      }
+    } else {
+      // This is a column breakpoint, so we are interested in all column
+      // offsets that correspond to the given line *and* column number.
+      for (let script of scripts) {
+        let columnToOffsetMap = script.getAllColumnOffsets()
+                                      .filter(({ lineNumber }) => {
+                                        return lineNumber === generatedLine;
+                                      });
+        for (let { columnNumber: column, offset } of columnToOffsetMap) {
+          if (column >= generatedColumn && column <= generatedLastColumn) {
+            entryPoints.push({ script, offsets: [offset] });
+          }
+        }
+      }
+    }
+
+    if (entryPoints.length === 0) {
+      return false;
+    }
+    setBreakpointAtEntryPoints(actor, entryPoints);
+    return true;
+  }
+});
+
+exports.SourceActor = SourceActor;
diff --git a/devtools/server/actors/storage.js b/devtools/server/actors/storage.js
new file mode 100644
index 000000000..572cd6b68
--- /dev/null
+++ b/devtools/server/actors/storage.js
@@ -0,0 +1,2542 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {Cc, Ci, Cu, CC} = require("chrome");
+const events = require("sdk/event/core");
+const protocol = require("devtools/shared/protocol");
+const {LongStringActor} = require("devtools/server/actors/string");
+const {DebuggerServer} = require("devtools/server/main");
+const Services = require("Services");
+const promise = require("promise");
+const {isWindowIncluded} = require("devtools/shared/layout/utils");
+const specs = require("devtools/shared/specs/storage");
+const { Task } = require("devtools/shared/task");
+
+loader.lazyImporter(this, "OS", "resource://gre/modules/osfile.jsm");
+loader.lazyImporter(this, "Sqlite", "resource://gre/modules/Sqlite.jsm");
+
+// We give this a funny name to avoid confusion with the global
+// indexedDB.
+loader.lazyGetter(this, "indexedDBForStorage", () => {
+  // On xpcshell, we can't instantiate indexedDB without crashing
+  try {
+    let sandbox
+      = Cu.Sandbox(CC("@mozilla.org/systemprincipal;1", "nsIPrincipal")(),
+                   {wantGlobalProperties: ["indexedDB"]});
+    return sandbox.indexedDB;
+  } catch (e) {
+    return {};
+  }
+});
+
+// Maximum number of cookies/local storage key-value-pairs that can be sent
+// over the wire to the client in one request.
+const MAX_STORE_OBJECT_COUNT = 50;
+// Delay for the batch job that sends the accumulated update packets to the
+// client (ms).
+const BATCH_DELAY = 200;
+
+// MAX_COOKIE_EXPIRY should be 2^63-1, but JavaScript can't handle that
+// precision.
+const MAX_COOKIE_EXPIRY = Math.pow(2, 62);
+
+// A RegExp for characters that cannot appear in a file/directory name. This is
+// used to sanitize the host name for indexed db to lookup whether the file is
+// present in <profileDir>/storage/default/ location
+var illegalFileNameCharacters = [
+  "[",
+  // Control characters \001 to \036
+  "\\x00-\\x24",
+  // Special characters
+  "/:*?\\\"<>|\\\\",
+  "]"
+].join("");
+var ILLEGAL_CHAR_REGEX = new RegExp(illegalFileNameCharacters, "g");
+
+// Holder for all the registered storage actors.
+var storageTypePool = new Map();
+
+/**
+ * An async method equivalent to setTimeout but using Promises
+ *
+ * @param {number} time
+ *        The wait time in milliseconds.
+ */
+function sleep(time) {
+  let deferred = promise.defer();
+
+  setTimeout(() => {
+    deferred.resolve(null);
+  }, time);
+
+  return deferred.promise;
+}
+
+// Helper methods to create a storage actor.
+var StorageActors = {};
+
+/**
+ * Creates a default object with the common methods required by all storage
+ * actors.
+ *
+ * This default object is missing a couple of required methods that should be
+ * implemented seperately for each actor. They are namely:
+ *   - observe : Method which gets triggered on the notificaiton of the watched
+ *               topic.
+ *   - getNamesForHost : Given a host, get list of all known store names.
+ *   - getValuesForHost : Given a host (and optianally a name) get all known
+ *                        store objects.
+ *   - toStoreObject : Given a store object, convert it to the required format
+ *                     so that it can be transferred over wire.
+ *   - populateStoresForHost : Given a host, populate the map of all store
+ *                             objects for it
+ *   - getFields: Given a subType(optional), get an array of objects containing
+ *                column field info. The info includes,
+ *                "name" is name of colume key.
+ *                "editable" is 1 means editable field; 0 means uneditable.
+ *
+ * @param {string} typeName
+ *        The typeName of the actor.
+ * @param {string} observationTopic
+ *        The topic which this actor listens to via Notification Observers.
+ */
+StorageActors.defaults = function (typeName, observationTopic) {
+  return {
+    typeName: typeName,
+
+    get conn() {
+      return this.storageActor.conn;
+    },
+
+    /**
+     * Returns a list of currently knwon hosts for the target window. This list
+     * contains unique hosts from the window + all inner windows.
+     */
+    get hosts() {
+      let hosts = new Set();
+      for (let {location} of this.storageActor.windows) {
+        hosts.add(this.getHostName(location));
+      }
+      return hosts;
+    },
+
+    /**
+     * Returns all the windows present on the page. Includes main window + inner
+     * iframe windows.
+     */
+    get windows() {
+      return this.storageActor.windows;
+    },
+
+    /**
+     * Converts the window.location object into host.
+     */
+    getHostName(location) {
+      return location.hostname || location.href;
+    },
+
+    initialize(storageActor) {
+      protocol.Actor.prototype.initialize.call(this, null);
+
+      this.storageActor = storageActor;
+
+      this.populateStoresForHosts();
+      if (observationTopic) {
+        Services.obs.addObserver(this, observationTopic, false);
+      }
+      this.onWindowReady = this.onWindowReady.bind(this);
+      this.onWindowDestroyed = this.onWindowDestroyed.bind(this);
+      events.on(this.storageActor, "window-ready", this.onWindowReady);
+      events.on(this.storageActor, "window-destroyed", this.onWindowDestroyed);
+    },
+
+    destroy() {
+      if (observationTopic) {
+        Services.obs.removeObserver(this, observationTopic, false);
+      }
+      events.off(this.storageActor, "window-ready", this.onWindowReady);
+      events.off(this.storageActor, "window-destroyed", this.onWindowDestroyed);
+
+      this.hostVsStores.clear();
+      this.storageActor = null;
+    },
+
+    getNamesForHost(host) {
+      return [...this.hostVsStores.get(host).keys()];
+    },
+
+    getValuesForHost(host, name) {
+      if (name) {
+        return [this.hostVsStores.get(host).get(name)];
+      }
+      return [...this.hostVsStores.get(host).values()];
+    },
+
+    getObjectsSize(host, names) {
+      return names.length;
+    },
+
+    /**
+     * When a new window is added to the page. This generally means that a new
+     * iframe is created, or the current window is completely reloaded.
+     *
+     * @param {window} window
+     *        The window which was added.
+     */
+    onWindowReady: Task.async(function* (window) {
+      let host = this.getHostName(window.location);
+      if (!this.hostVsStores.has(host)) {
+        yield this.populateStoresForHost(host, window);
+        let data = {};
+        data[host] = this.getNamesForHost(host);
+        this.storageActor.update("added", typeName, data);
+      }
+    }),
+
+    /**
+     * When a window is removed from the page. This generally means that an
+     * iframe was removed, or the current window reload is triggered.
+     *
+     * @param {window} window
+     *        The window which was removed.
+     */
+    onWindowDestroyed(window) {
+      if (!window.location) {
+        // Nothing can be done if location object is null
+        return;
+      }
+      let host = this.getHostName(window.location);
+      if (!this.hosts.has(host)) {
+        this.hostVsStores.delete(host);
+        let data = {};
+        data[host] = [];
+        this.storageActor.update("deleted", typeName, data);
+      }
+    },
+
+    form(form, detail) {
+      if (detail === "actorid") {
+        return this.actorID;
+      }
+
+      let hosts = {};
+      for (let host of this.hosts) {
+        hosts[host] = [];
+      }
+
+      return {
+        actor: this.actorID,
+        hosts: hosts
+      };
+    },
+
+    /**
+     * Populates a map of known hosts vs a map of stores vs value.
+     */
+    populateStoresForHosts() {
+      this.hostVsStores = new Map();
+      for (let host of this.hosts) {
+        this.populateStoresForHost(host);
+      }
+    },
+
+    /**
+     * Returns a list of requested store objects. Maximum values returned are
+     * MAX_STORE_OBJECT_COUNT. This method returns paginated values whose
+     * starting index and total size can be controlled via the options object
+     *
+     * @param {string} host
+     *        The host name for which the store values are required.
+     * @param {array:string} names
+     *        Array containing the names of required store objects. Empty if all
+     *        items are required.
+     * @param {object} options
+     *        Additional options for the request containing following
+     *        properties:
+     *         - offset {number} : The begin index of the returned array amongst
+     *                  the total values
+     *         - size {number} : The number of values required.
+     *         - sortOn {string} : The values should be sorted on this property.
+     *         - index {string} : In case of indexed db, the IDBIndex to be used
+     *                 for fetching the values.
+     *
+     * @return {object} An object containing following properties:
+     *          - offset - The actual offset of the returned array. This might
+     *                     be different from the requested offset if that was
+     *                     invalid
+     *          - total - The total number of entries possible.
+     *          - data - The requested values.
+     */
+    getStoreObjects: Task.async(function* (host, names, options = {}) {
+      let offset = options.offset || 0;
+      let size = options.size || MAX_STORE_OBJECT_COUNT;
+      if (size > MAX_STORE_OBJECT_COUNT) {
+        size = MAX_STORE_OBJECT_COUNT;
+      }
+      let sortOn = options.sortOn || "name";
+
+      let toReturn = {
+        offset: offset,
+        total: 0,
+        data: []
+      };
+
+      let principal = null;
+      if (this.typeName === "indexedDB") {
+        // We only acquire principal when the type of the storage is indexedDB
+        // because the principal only matters the indexedDB.
+        let win = this.storageActor.getWindowFromHost(host);
+        if (win) {
+          principal = win.document.nodePrincipal;
+        }
+      }
+
+      if (names) {
+        for (let name of names) {
+          let values = yield this.getValuesForHost(host, name, options,
+            this.hostVsStores, principal);
+
+          let {result, objectStores} = values;
+
+          if (result && typeof result.objectsSize !== "undefined") {
+            for (let {key, count} of result.objectsSize) {
+              this.objectsSize[key] = count;
+            }
+          }
+
+          if (result) {
+            toReturn.data.push(...result.data);
+          } else if (objectStores) {
+            toReturn.data.push(...objectStores);
+          } else {
+            toReturn.data.push(...values);
+          }
+        }
+        toReturn.total = this.getObjectsSize(host, names, options);
+        if (offset > toReturn.total) {
+          // In this case, toReturn.data is an empty array.
+          toReturn.offset = toReturn.total;
+          toReturn.data = [];
+        } else {
+          toReturn.data = toReturn.data.sort((a, b) => {
+            return a[sortOn] - b[sortOn];
+          }).slice(offset, offset + size).map(a => this.toStoreObject(a));
+        }
+      } else {
+        let obj = yield this.getValuesForHost(host, undefined, undefined,
+                                              this.hostVsStores, principal);
+        if (obj.dbs) {
+          obj = obj.dbs;
+        }
+
+        toReturn.total = obj.length;
+        if (offset > toReturn.total) {
+          // In this case, toReturn.data is an empty array.
+          toReturn.offset = offset = toReturn.total;
+          toReturn.data = [];
+        } else {
+          toReturn.data = obj.sort((a, b) => {
+            return a[sortOn] - b[sortOn];
+          }).slice(offset, offset + size)
+            .map(object => this.toStoreObject(object));
+        }
+      }
+
+      return toReturn;
+    })
+  };
+};
+
+/**
+ * Creates an actor and its corresponding front and registers it to the Storage
+ * Actor.
+ *
+ * @See StorageActors.defaults()
+ *
+ * @param {object} options
+ *        Options required by StorageActors.defaults method which are :
+ *         - typeName {string}
+ *                    The typeName of the actor.
+ *         - observationTopic {string}
+ *                            The topic which this actor listens to via
+ *                            Notification Observers.
+ * @param {object} overrides
+ *        All the methods which you want to be different from the ones in
+ *        StorageActors.defaults method plus the required ones described there.
+ */
+StorageActors.createActor = function (options = {}, overrides = {}) {
+  let actorObject = StorageActors.defaults(
+    options.typeName,
+    options.observationTopic || null
+  );
+  for (let key in overrides) {
+    actorObject[key] = overrides[key];
+  }
+
+  let actorSpec = specs.childSpecs[options.typeName];
+  let actor = protocol.ActorClassWithSpec(actorSpec, actorObject);
+  storageTypePool.set(actorObject.typeName, actor);
+};
+
+/**
+ * The Cookies actor and front.
+ */
+StorageActors.createActor({
+  typeName: "cookies"
+}, {
+  initialize(storageActor) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this.storageActor = storageActor;
+
+    this.maybeSetupChildProcess();
+    this.populateStoresForHosts();
+    this.addCookieObservers();
+
+    this.onWindowReady = this.onWindowReady.bind(this);
+    this.onWindowDestroyed = this.onWindowDestroyed.bind(this);
+    events.on(this.storageActor, "window-ready", this.onWindowReady);
+    events.on(this.storageActor, "window-destroyed", this.onWindowDestroyed);
+  },
+
+  destroy() {
+    this.hostVsStores.clear();
+
+    // We need to remove the cookie listeners early in E10S mode so we need to
+    // use a conditional here to ensure that we only attempt to remove them in
+    // single process mode.
+    if (!DebuggerServer.isInChildProcess) {
+      this.removeCookieObservers();
+    }
+
+    events.off(this.storageActor, "window-ready", this.onWindowReady);
+    events.off(this.storageActor, "window-destroyed", this.onWindowDestroyed);
+
+    this._pendingResponse = this.storageActor = null;
+  },
+
+  /**
+   * Given a cookie object, figure out all the matching hosts from the page that
+   * the cookie belong to.
+   */
+  getMatchingHosts(cookies) {
+    if (!cookies.length) {
+      cookies = [cookies];
+    }
+    let hosts = new Set();
+    for (let host of this.hosts) {
+      for (let cookie of cookies) {
+        if (this.isCookieAtHost(cookie, host)) {
+          hosts.add(host);
+        }
+      }
+    }
+    return [...hosts];
+  },
+
+  /**
+   * Given a cookie object and a host, figure out if the cookie is valid for
+   * that host.
+   */
+  isCookieAtHost(cookie, host) {
+    if (cookie.host == null) {
+      return host == null;
+    }
+    if (cookie.host.startsWith(".")) {
+      return ("." + host).endsWith(cookie.host);
+    }
+    if (cookie.host === "") {
+      return host.startsWith("file://" + cookie.path);
+    }
+    return cookie.host == host;
+  },
+
+  toStoreObject(cookie) {
+    if (!cookie) {
+      return null;
+    }
+
+    return {
+      name: cookie.name,
+      path: cookie.path || "",
+      host: cookie.host || "",
+
+      // because expires is in seconds
+      expires: (cookie.expires || 0) * 1000,
+
+      // because it is in micro seconds
+      creationTime: cookie.creationTime / 1000,
+
+      // - do -
+      lastAccessed: cookie.lastAccessed / 1000,
+      value: new LongStringActor(this.conn, cookie.value || ""),
+      isDomain: cookie.isDomain,
+      isSecure: cookie.isSecure,
+      isHttpOnly: cookie.isHttpOnly
+    };
+  },
+
+  populateStoresForHost(host) {
+    this.hostVsStores.set(host, new Map());
+    let doc = this.storageActor.document;
+
+    let cookies = this.getCookiesFromHost(host, doc.nodePrincipal
+                                                   .originAttributes);
+
+    for (let cookie of cookies) {
+      if (this.isCookieAtHost(cookie, host)) {
+        this.hostVsStores.get(host).set(cookie.name, cookie);
+      }
+    }
+  },
+
+  /**
+   * Notification observer for "cookie-change".
+   *
+   * @param subject
+   *        {Cookie|[Array]} A JSON parsed object containing either a single
+   *        cookie representation or an array. Array is only in case of
+   *        a "batch-deleted" action.
+   * @param {string} topic
+   *        The topic of the notification.
+   * @param {string} action
+   *        Additional data associated with the notification. Its the type of
+   *        cookie change in the "cookie-change" topic.
+   */
+  onCookieChanged(subject, topic, action) {
+    if (topic !== "cookie-changed" ||
+        !this.storageActor ||
+        !this.storageActor.windows) {
+      return null;
+    }
+
+    let hosts = this.getMatchingHosts(subject);
+    let data = {};
+
+    switch (action) {
+      case "added":
+      case "changed":
+        if (hosts.length) {
+          for (let host of hosts) {
+            this.hostVsStores.get(host).set(subject.name, subject);
+            data[host] = [subject.name];
+          }
+          this.storageActor.update(action, "cookies", data);
+        }
+        break;
+
+      case "deleted":
+        if (hosts.length) {
+          for (let host of hosts) {
+            this.hostVsStores.get(host).delete(subject.name);
+            data[host] = [subject.name];
+          }
+          this.storageActor.update("deleted", "cookies", data);
+        }
+        break;
+
+      case "batch-deleted":
+        if (hosts.length) {
+          for (let host of hosts) {
+            let stores = [];
+            for (let cookie of subject) {
+              this.hostVsStores.get(host).delete(cookie.name);
+              stores.push(cookie.name);
+            }
+            data[host] = stores;
+          }
+          this.storageActor.update("deleted", "cookies", data);
+        }
+        break;
+
+      case "cleared":
+        if (hosts.length) {
+          for (let host of hosts) {
+            data[host] = [];
+          }
+          this.storageActor.update("cleared", "cookies", data);
+        }
+        break;
+    }
+    return null;
+  },
+
+  getFields: Task.async(function* () {
+    return [
+      { name: "name", editable: 1},
+      { name: "path", editable: 1},
+      { name: "host", editable: 1},
+      { name: "expires", editable: 1},
+      { name: "lastAccessed", editable: 0},
+      { name: "value", editable: 1},
+      { name: "isDomain", editable: 0},
+      { name: "isSecure", editable: 1},
+      { name: "isHttpOnly", editable: 1}
+    ];
+  }),
+
+  /**
+   * Pass the editItem command from the content to the chrome process.
+   *
+   * @param {Object} data
+   *        See editCookie() for format details.
+   */
+  editItem: Task.async(function* (data) {
+    let doc = this.storageActor.document;
+    data.originAttributes = doc.nodePrincipal
+                               .originAttributes;
+    this.editCookie(data);
+  }),
+
+  removeItem: Task.async(function* (host, name) {
+    let doc = this.storageActor.document;
+    this.removeCookie(host, name, doc.nodePrincipal
+                                     .originAttributes);
+  }),
+
+  removeAll: Task.async(function* (host, domain) {
+    let doc = this.storageActor.document;
+    this.removeAllCookies(host, domain, doc.nodePrincipal
+                                           .originAttributes);
+  }),
+
+  maybeSetupChildProcess() {
+    cookieHelpers.onCookieChanged = this.onCookieChanged.bind(this);
+
+    if (!DebuggerServer.isInChildProcess) {
+      this.getCookiesFromHost =
+        cookieHelpers.getCookiesFromHost.bind(cookieHelpers);
+      this.addCookieObservers =
+        cookieHelpers.addCookieObservers.bind(cookieHelpers);
+      this.removeCookieObservers =
+        cookieHelpers.removeCookieObservers.bind(cookieHelpers);
+      this.editCookie =
+        cookieHelpers.editCookie.bind(cookieHelpers);
+      this.removeCookie =
+        cookieHelpers.removeCookie.bind(cookieHelpers);
+      this.removeAllCookies =
+        cookieHelpers.removeAllCookies.bind(cookieHelpers);
+      return;
+    }
+
+    const { sendSyncMessage, addMessageListener } =
+      this.conn.parentMessageManager;
+
+    this.conn.setupInParent({
+      module: "devtools/server/actors/storage",
+      setupParent: "setupParentProcessForCookies"
+    });
+
+    this.getCookiesFromHost =
+      callParentProcess.bind(null, "getCookiesFromHost");
+    this.addCookieObservers =
+      callParentProcess.bind(null, "addCookieObservers");
+    this.removeCookieObservers =
+      callParentProcess.bind(null, "removeCookieObservers");
+    this.editCookie =
+      callParentProcess.bind(null, "editCookie");
+    this.removeCookie =
+      callParentProcess.bind(null, "removeCookie");
+    this.removeAllCookies =
+      callParentProcess.bind(null, "removeAllCookies");
+
+    addMessageListener("debug:storage-cookie-request-child",
+                       cookieHelpers.handleParentRequest);
+
+    function callParentProcess(methodName, ...args) {
+      let reply = sendSyncMessage("debug:storage-cookie-request-parent", {
+        method: methodName,
+        args: args
+      });
+
+      if (reply.length === 0) {
+        console.error("ERR_DIRECTOR_CHILD_NO_REPLY from " + methodName);
+      } else if (reply.length > 1) {
+        console.error("ERR_DIRECTOR_CHILD_MULTIPLE_REPLIES from " + methodName);
+      }
+
+      let result = reply[0];
+
+      if (methodName === "getCookiesFromHost") {
+        return JSON.parse(result);
+      }
+
+      return result;
+    }
+  },
+});
+
+var cookieHelpers = {
+  getCookiesFromHost(host, originAttributes) {
+    // Local files have no host.
+    if (host.startsWith("file:///")) {
+      host = "";
+    }
+
+    let cookies = Services.cookies.getCookiesFromHost(host, originAttributes);
+    let store = [];
+
+    while (cookies.hasMoreElements()) {
+      let cookie = cookies.getNext().QueryInterface(Ci.nsICookie2);
+
+      store.push(cookie);
+    }
+
+    return store;
+  },
+
+  /**
+   * Apply the results of a cookie edit.
+   *
+   * @param {Object} data
+   *        An object in the following format:
+   *        {
+   *          host: "http://www.mozilla.org",
+   *          field: "value",
+   *          key: "name",
+   *          oldValue: "%7BHello%7D",
+   *          newValue: "%7BHelloo%7D",
+   *          items: {
+   *            name: "optimizelyBuckets",
+   *            path: "/",
+   *            host: ".mozilla.org",
+   *            expires: "Mon, 02 Jun 2025 12:37:37 GMT",
+   *            creationTime: "Tue, 18 Nov 2014 16:21:18 GMT",
+   *            lastAccessed: "Wed, 17 Feb 2016 10:06:23 GMT",
+   *            value: "%7BHelloo%7D",
+   *            isDomain: "true",
+   *            isSecure: "false",
+   *            isHttpOnly: "false"
+   *          }
+   *        }
+   */
+  editCookie(data) {
+    let {field, oldValue, newValue} = data;
+    let origName = field === "name" ? oldValue : data.items.name;
+    let origHost = field === "host" ? oldValue : data.items.host;
+    let origPath = field === "path" ? oldValue : data.items.path;
+    let cookie = null;
+
+    let enumerator = Services.cookies.getCookiesFromHost(origHost, data.originAttributes || {});
+    while (enumerator.hasMoreElements()) {
+      let nsiCookie = enumerator.getNext().QueryInterface(Ci.nsICookie2);
+      if (nsiCookie.name === origName && nsiCookie.host === origHost) {
+        cookie = {
+          host: nsiCookie.host,
+          path: nsiCookie.path,
+          name: nsiCookie.name,
+          value: nsiCookie.value,
+          isSecure: nsiCookie.isSecure,
+          isHttpOnly: nsiCookie.isHttpOnly,
+          isSession: nsiCookie.isSession,
+          expires: nsiCookie.expires,
+          originAttributes: nsiCookie.originAttributes
+        };
+        break;
+      }
+    }
+
+    if (!cookie) {
+      return;
+    }
+
+    // If the date is expired set it for 1 minute in the future.
+    let now = new Date();
+    if (!cookie.isSession && (cookie.expires * 1000) <= now) {
+      let tenSecondsFromNow = (now.getTime() + 10 * 1000) / 1000;
+
+      cookie.expires = tenSecondsFromNow;
+    }
+
+    switch (field) {
+      case "isSecure":
+      case "isHttpOnly":
+      case "isSession":
+        newValue = newValue === "true";
+        break;
+
+      case "expires":
+        newValue = Date.parse(newValue) / 1000;
+
+        if (isNaN(newValue)) {
+          newValue = MAX_COOKIE_EXPIRY;
+        }
+        break;
+
+      case "host":
+      case "name":
+      case "path":
+        // Remove the edited cookie.
+        Services.cookies.remove(origHost, origName, origPath,
+                                false, cookie.originAttributes);
+        break;
+    }
+
+    // Apply changes.
+    cookie[field] = newValue;
+
+    // cookie.isSession is not always set correctly on session cookies so we
+    // need to trust cookie.expires instead.
+    cookie.isSession = !cookie.expires;
+
+    // Add the edited cookie.
+    Services.cookies.add(
+      cookie.host,
+      cookie.path,
+      cookie.name,
+      cookie.value,
+      cookie.isSecure,
+      cookie.isHttpOnly,
+      cookie.isSession,
+      cookie.isSession ? MAX_COOKIE_EXPIRY : cookie.expires,
+      cookie.originAttributes
+    );
+  },
+
+  _removeCookies(host, opts = {}) {
+    function hostMatches(cookieHost, matchHost) {
+      if (cookieHost == null) {
+        return matchHost == null;
+      }
+      if (cookieHost.startsWith(".")) {
+        return ("." + matchHost).endsWith(cookieHost);
+      }
+      return cookieHost == host;
+    }
+
+    let enumerator = Services.cookies.getCookiesFromHost(host, opts.originAttributes || {});
+    while (enumerator.hasMoreElements()) {
+      let cookie = enumerator.getNext().QueryInterface(Ci.nsICookie2);
+      if (hostMatches(cookie.host, host) &&
+          (!opts.name || cookie.name === opts.name) &&
+          (!opts.domain || cookie.host === opts.domain)) {
+        Services.cookies.remove(
+          cookie.host,
+          cookie.name,
+          cookie.path,
+          false,
+          cookie.originAttributes
+        );
+      }
+    }
+  },
+
+  removeCookie(host, name, originAttributes) {
+    if (name !== undefined) {
+      this._removeCookies(host, { name, originAttributes });
+    }
+  },
+
+  removeAllCookies(host, domain, originAttributes) {
+    this._removeCookies(host, { domain, originAttributes });
+  },
+
+  addCookieObservers() {
+    Services.obs.addObserver(cookieHelpers, "cookie-changed", false);
+    return null;
+  },
+
+  removeCookieObservers() {
+    Services.obs.removeObserver(cookieHelpers, "cookie-changed", false);
+    return null;
+  },
+
+  observe(subject, topic, data) {
+    if (!subject) {
+      return;
+    }
+
+    switch (topic) {
+      case "cookie-changed":
+        if (data === "batch-deleted") {
+          let cookiesNoInterface = subject.QueryInterface(Ci.nsIArray);
+          let cookies = [];
+
+          for (let i = 0; i < cookiesNoInterface.length; i++) {
+            let cookie = cookiesNoInterface.queryElementAt(i, Ci.nsICookie2);
+            cookies.push(cookie);
+          }
+          cookieHelpers.onCookieChanged(cookies, topic, data);
+
+          return;
+        }
+
+        let cookie = subject.QueryInterface(Ci.nsICookie2);
+        cookieHelpers.onCookieChanged(cookie, topic, data);
+        break;
+    }
+  },
+
+  handleParentRequest(msg) {
+    switch (msg.json.method) {
+      case "onCookieChanged":
+        let [cookie, topic, data] = msg.data.args;
+        cookie = JSON.parse(cookie);
+        cookieHelpers.onCookieChanged(cookie, topic, data);
+        break;
+    }
+  },
+
+  handleChildRequest(msg) {
+    switch (msg.json.method) {
+      case "getCookiesFromHost": {
+        let host = msg.data.args[0];
+        let originAttributes = msg.data.args[1];
+        let cookies = cookieHelpers.getCookiesFromHost(host, originAttributes);
+        return JSON.stringify(cookies);
+      }
+      case "addCookieObservers": {
+        return cookieHelpers.addCookieObservers();
+      }
+      case "removeCookieObservers": {
+        return cookieHelpers.removeCookieObservers();
+      }
+      case "editCookie": {
+        let rowdata = msg.data.args[0];
+        return cookieHelpers.editCookie(rowdata);
+      }
+      case "removeCookie": {
+        let host = msg.data.args[0];
+        let name = msg.data.args[1];
+        let originAttributes = msg.data.args[2];
+        return cookieHelpers.removeCookie(host, name, originAttributes);
+      }
+      case "removeAllCookies": {
+        let host = msg.data.args[0];
+        let domain = msg.data.args[1];
+        let originAttributes = msg.data.args[2];
+        return cookieHelpers.removeAllCookies(host, domain, originAttributes);
+      }
+      default:
+        console.error("ERR_DIRECTOR_PARENT_UNKNOWN_METHOD", msg.json.method);
+        throw new Error("ERR_DIRECTOR_PARENT_UNKNOWN_METHOD");
+    }
+  },
+};
+
+/**
+ * E10S parent/child setup helpers
+ */
+
+exports.setupParentProcessForCookies = function ({ mm, prefix }) {
+  cookieHelpers.onCookieChanged =
+    callChildProcess.bind(null, "onCookieChanged");
+
+  // listen for director-script requests from the child process
+  setMessageManager(mm);
+
+  function callChildProcess(methodName, ...args) {
+    if (methodName === "onCookieChanged") {
+      args[0] = JSON.stringify(args[0]);
+    }
+
+    try {
+      mm.sendAsyncMessage("debug:storage-cookie-request-child", {
+        method: methodName,
+        args: args
+      });
+    } catch (e) {
+      // We may receive a NS_ERROR_NOT_INITIALIZED if the target window has
+      // been closed. This can legitimately happen in between test runs.
+    }
+  }
+
+  function setMessageManager(newMM) {
+    if (mm) {
+      mm.removeMessageListener("debug:storage-cookie-request-parent",
+                               cookieHelpers.handleChildRequest);
+    }
+    mm = newMM;
+    if (mm) {
+      mm.addMessageListener("debug:storage-cookie-request-parent",
+                            cookieHelpers.handleChildRequest);
+    }
+  }
+
+  return {
+    onBrowserSwap: setMessageManager,
+    onDisconnected: () => {
+      // Although "disconnected-from-child" implies that the child is already
+      // disconnected this is not the case. The disconnection takes place after
+      // this method has finished. This gives us chance to clean up items within
+      // the parent process e.g. observers.
+      cookieHelpers.removeCookieObservers();
+      setMessageManager(null);
+    }
+  };
+};
+
+/**
+ * Helper method to create the overriden object required in
+ * StorageActors.createActor for Local Storage and Session Storage.
+ * This method exists as both Local Storage and Session Storage have almost
+ * identical actors.
+ */
+function getObjectForLocalOrSessionStorage(type) {
+  return {
+    getNamesForHost(host) {
+      let storage = this.hostVsStores.get(host);
+      return storage ? Object.keys(storage) : [];
+    },
+
+    getValuesForHost(host, name) {
+      let storage = this.hostVsStores.get(host);
+      if (!storage) {
+        return [];
+      }
+      if (name) {
+        let value = storage ? storage.getItem(name) : null;
+        return [{ name, value }];
+      }
+      if (!storage) {
+        return [];
+      }
+      return Object.keys(storage).map(key => ({
+        name: key,
+        value: storage.getItem(key)
+      }));
+    },
+
+    getHostName(location) {
+      if (!location.host) {
+        return location.href;
+      }
+      return location.protocol + "//" + location.host;
+    },
+
+    populateStoresForHost(host, window) {
+      try {
+        this.hostVsStores.set(host, window[type]);
+      } catch (ex) {
+        console.warn(`Failed to enumerate ${type} for host ${host}: ${ex}`);
+      }
+    },
+
+    populateStoresForHosts() {
+      this.hostVsStores = new Map();
+      for (let window of this.windows) {
+        this.populateStoresForHost(this.getHostName(window.location), window);
+      }
+    },
+
+    getFields: Task.async(function* () {
+      return [
+        { name: "name", editable: 1},
+        { name: "value", editable: 1}
+      ];
+    }),
+
+    /**
+     * Edit localStorage or sessionStorage fields.
+     *
+     * @param {Object} data
+     *        See editCookie() for format details.
+     */
+    editItem: Task.async(function* ({host, field, oldValue, items}) {
+      let storage = this.hostVsStores.get(host);
+      if (!storage) {
+        return;
+      }
+
+      if (field === "name") {
+        storage.removeItem(oldValue);
+      }
+
+      storage.setItem(items.name, items.value);
+    }),
+
+    removeItem: Task.async(function* (host, name) {
+      let storage = this.hostVsStores.get(host);
+      if (!storage) {
+        return;
+      }
+      storage.removeItem(name);
+    }),
+
+    removeAll: Task.async(function* (host) {
+      let storage = this.hostVsStores.get(host);
+      if (!storage) {
+        return;
+      }
+      storage.clear();
+    }),
+
+    observe(subject, topic, data) {
+      if (topic != "dom-storage2-changed" || data != type) {
+        return null;
+      }
+
+      let host = this.getSchemaAndHost(subject.url);
+
+      if (!this.hostVsStores.has(host)) {
+        return null;
+      }
+
+      let action = "changed";
+      if (subject.key == null) {
+        return this.storageActor.update("cleared", type, [host]);
+      } else if (subject.oldValue == null) {
+        action = "added";
+      } else if (subject.newValue == null) {
+        action = "deleted";
+      }
+      let updateData = {};
+      updateData[host] = [subject.key];
+      return this.storageActor.update(action, type, updateData);
+    },
+
+    /**
+     * Given a url, correctly determine its protocol + hostname part.
+     */
+    getSchemaAndHost(url) {
+      let uri = Services.io.newURI(url, null, null);
+      if (!uri.host) {
+        return uri.spec;
+      }
+      return uri.scheme + "://" + uri.hostPort;
+    },
+
+    toStoreObject(item) {
+      if (!item) {
+        return null;
+      }
+
+      return {
+        name: item.name,
+        value: new LongStringActor(this.conn, item.value || "")
+      };
+    },
+  };
+}
+
+/**
+ * The Local Storage actor and front.
+ */
+StorageActors.createActor({
+  typeName: "localStorage",
+  observationTopic: "dom-storage2-changed"
+}, getObjectForLocalOrSessionStorage("localStorage"));
+
+/**
+ * The Session Storage actor and front.
+ */
+StorageActors.createActor({
+  typeName: "sessionStorage",
+  observationTopic: "dom-storage2-changed"
+}, getObjectForLocalOrSessionStorage("sessionStorage"));
+
+StorageActors.createActor({
+  typeName: "Cache"
+}, {
+  getCachesForHost: Task.async(function* (host) {
+    let uri = Services.io.newURI(host, null, null);
+    let principal =
+      Services.scriptSecurityManager.getNoAppCodebasePrincipal(uri);
+
+    // The first argument tells if you want to get |content| cache or |chrome|
+    // cache.
+    // The |content| cache is the cache explicitely named by the web content
+    // (service worker or web page).
+    // The |chrome| cache is the cache implicitely cached by the platform,
+    // hosting the source file of the service worker.
+    let { CacheStorage } = this.storageActor.window;
+    let cache = new CacheStorage("content", principal);
+    return cache;
+  }),
+
+  preListStores: Task.async(function* () {
+    for (let host of this.hosts) {
+      yield this.populateStoresForHost(host);
+    }
+  }),
+
+  form(form, detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    let hosts = {};
+    for (let host of this.hosts) {
+      hosts[host] = this.getNamesForHost(host);
+    }
+
+    return {
+      actor: this.actorID,
+      hosts: hosts
+    };
+  },
+
+  getNamesForHost(host) {
+    // UI code expect each name to be a JSON string of an array :/
+    return [...this.hostVsStores.get(host).keys()].map(a => {
+      return JSON.stringify([a]);
+    });
+  },
+
+  getValuesForHost: Task.async(function* (host, name) {
+    if (!name) {
+      return [];
+    }
+    // UI is weird and expect a JSON stringified array... and pass it back :/
+    name = JSON.parse(name)[0];
+
+    let cache = this.hostVsStores.get(host).get(name);
+    let requests = yield cache.keys();
+    let results = [];
+    for (let request of requests) {
+      let response = yield cache.match(request);
+      // Unwrap the response to get access to all its properties if the
+      // response happen to be 'opaque', when it is a Cross Origin Request.
+      response = response.cloneUnfiltered();
+      results.push(yield this.processEntry(request, response));
+    }
+    return results;
+  }),
+
+  processEntry: Task.async(function* (request, response) {
+    return {
+      url: String(request.url),
+      status: String(response.statusText),
+    };
+  }),
+
+  getFields: Task.async(function* () {
+    return [
+      { name: "url", editable: 0 },
+      { name: "status", editable: 0 }
+    ];
+  }),
+
+  getHostName(location) {
+    if (!location.host) {
+      return location.href;
+    }
+    return location.protocol + "//" + location.host;
+  },
+
+  populateStoresForHost: Task.async(function* (host) {
+    let storeMap = new Map();
+    let caches = yield this.getCachesForHost(host);
+    try {
+      for (let name of (yield caches.keys())) {
+        storeMap.set(name, (yield caches.open(name)));
+      }
+    } catch (ex) {
+      console.warn(`Failed to enumerate CacheStorage for host ${host}: ${ex}`);
+    }
+    this.hostVsStores.set(host, storeMap);
+  }),
+
+  /**
+   * This method is overriden and left blank as for Cache Storage, this
+   * operation cannot be performed synchronously. Thus, the preListStores
+   * method exists to do the same task asynchronously.
+   */
+  populateStoresForHosts() {
+    this.hostVsStores = new Map();
+  },
+
+  /**
+   * Given a url, correctly determine its protocol + hostname part.
+   */
+  getSchemaAndHost(url) {
+    let uri = Services.io.newURI(url, null, null);
+    return uri.scheme + "://" + uri.hostPort;
+  },
+
+  toStoreObject(item) {
+    return item;
+  },
+
+  removeItem: Task.async(function* (host, name) {
+    const cacheMap = this.hostVsStores.get(host);
+    if (!cacheMap) {
+      return;
+    }
+
+    const parsedName = JSON.parse(name);
+
+    if (parsedName.length == 1) {
+      // Delete the whole Cache object
+      const [ cacheName ] = parsedName;
+      cacheMap.delete(cacheName);
+      const cacheStorage = yield this.getCachesForHost(host);
+      yield cacheStorage.delete(cacheName);
+      this.onItemUpdated("deleted", host, [ cacheName ]);
+    } else if (parsedName.length == 2) {
+      // Delete one cached request
+      const [ cacheName, url ] = parsedName;
+      const cache = cacheMap.get(cacheName);
+      if (cache) {
+        yield cache.delete(url);
+        this.onItemUpdated("deleted", host, [ cacheName, url ]);
+      }
+    }
+  }),
+
+  removeAll: Task.async(function* (host, name) {
+    const cacheMap = this.hostVsStores.get(host);
+    if (!cacheMap) {
+      return;
+    }
+
+    const parsedName = JSON.parse(name);
+
+    // Only a Cache object is a valid object to clear
+    if (parsedName.length == 1) {
+      const [ cacheName ] = parsedName;
+      const cache = cacheMap.get(cacheName);
+      if (cache) {
+        let keys = yield cache.keys();
+        yield promise.all(keys.map(key => cache.delete(key)));
+        this.onItemUpdated("cleared", host, [ cacheName ]);
+      }
+    }
+  }),
+
+  /**
+   * CacheStorage API doesn't support any notifications, we must fake them
+   */
+  onItemUpdated(action, host, path) {
+    this.storageActor.update(action, "Cache", {
+      [host]: [ JSON.stringify(path) ]
+    });
+  },
+});
+
+/**
+ * Code related to the Indexed DB actor and front
+ */
+
+// Metadata holder objects for various components of Indexed DB
+
+/**
+ * Meta data object for a particular index in an object store
+ *
+ * @param {IDBIndex} index
+ *        The particular index from the object store.
+ */
+function IndexMetadata(index) {
+  this._name = index.name;
+  this._keyPath = index.keyPath;
+  this._unique = index.unique;
+  this._multiEntry = index.multiEntry;
+}
+IndexMetadata.prototype = {
+  toObject() {
+    return {
+      name: this._name,
+      keyPath: this._keyPath,
+      unique: this._unique,
+      multiEntry: this._multiEntry
+    };
+  }
+};
+
+/**
+ * Meta data object for a particular object store in a db
+ *
+ * @param {IDBObjectStore} objectStore
+ *        The particular object store from the db.
+ */
+function ObjectStoreMetadata(objectStore) {
+  this._name = objectStore.name;
+  this._keyPath = objectStore.keyPath;
+  this._autoIncrement = objectStore.autoIncrement;
+  this._indexes = [];
+
+  for (let i = 0; i < objectStore.indexNames.length; i++) {
+    let index = objectStore.index(objectStore.indexNames[i]);
+
+    let newIndex = {
+      keypath: index.keyPath,
+      multiEntry: index.multiEntry,
+      name: index.name,
+      objectStore: {
+        autoIncrement: index.objectStore.autoIncrement,
+        indexNames: [...index.objectStore.indexNames],
+        keyPath: index.objectStore.keyPath,
+        name: index.objectStore.name,
+      }
+    };
+
+    this._indexes.push([newIndex, new IndexMetadata(index)]);
+  }
+}
+ObjectStoreMetadata.prototype = {
+  toObject() {
+    return {
+      name: this._name,
+      keyPath: this._keyPath,
+      autoIncrement: this._autoIncrement,
+      indexes: JSON.stringify(
+        [...this._indexes.values()].map(index => index.toObject())
+      )
+    };
+  }
+};
+
+/**
+ * Meta data object for a particular indexed db in a host.
+ *
+ * @param {string} origin
+ *        The host associated with this indexed db.
+ * @param {IDBDatabase} db
+ *        The particular indexed db.
+ */
+function DatabaseMetadata(origin, db) {
+  this._origin = origin;
+  this._name = db.name;
+  this._version = db.version;
+  this._objectStores = [];
+
+  if (db.objectStoreNames.length) {
+    let transaction = db.transaction(db.objectStoreNames, "readonly");
+
+    for (let i = 0; i < transaction.objectStoreNames.length; i++) {
+      let objectStore =
+        transaction.objectStore(transaction.objectStoreNames[i]);
+      this._objectStores.push([transaction.objectStoreNames[i],
+                              new ObjectStoreMetadata(objectStore)]);
+    }
+  }
+}
+DatabaseMetadata.prototype = {
+  get objectStores() {
+    return this._objectStores;
+  },
+
+  toObject() {
+    return {
+      name: this._name,
+      origin: this._origin,
+      version: this._version,
+      objectStores: this._objectStores.size
+    };
+  }
+};
+
+StorageActors.createActor({
+  typeName: "indexedDB"
+}, {
+  initialize(storageActor) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this.storageActor = storageActor;
+
+    this.maybeSetupChildProcess();
+
+    this.objectsSize = {};
+    this.storageActor = storageActor;
+    this.onWindowReady = this.onWindowReady.bind(this);
+    this.onWindowDestroyed = this.onWindowDestroyed.bind(this);
+
+    events.on(this.storageActor, "window-ready", this.onWindowReady);
+    events.on(this.storageActor, "window-destroyed", this.onWindowDestroyed);
+  },
+
+  destroy() {
+    this.hostVsStores.clear();
+    this.objectsSize = null;
+
+    events.off(this.storageActor, "window-ready", this.onWindowReady);
+    events.off(this.storageActor, "window-destroyed", this.onWindowDestroyed);
+  },
+
+  /**
+   * Remove an indexedDB database from given host with a given name.
+   */
+  removeDatabase: Task.async(function* (host, name) {
+    let win = this.storageActor.getWindowFromHost(host);
+    if (!win) {
+      return { error: `Window for host ${host} not found` };
+    }
+
+    let principal = win.document.nodePrincipal;
+    return this.removeDB(host, principal, name);
+  }),
+
+  removeAll: Task.async(function* (host, name) {
+    let [db, store] = JSON.parse(name);
+
+    let win = this.storageActor.getWindowFromHost(host);
+    if (!win) {
+      return;
+    }
+
+    let principal = win.document.nodePrincipal;
+    this.clearDBStore(host, principal, db, store);
+  }),
+
+  removeItem: Task.async(function* (host, name) {
+    let [db, store, id] = JSON.parse(name);
+
+    let win = this.storageActor.getWindowFromHost(host);
+    if (!win) {
+      return;
+    }
+
+    let principal = win.document.nodePrincipal;
+    this.removeDBRecord(host, principal, db, store, id);
+  }),
+
+  getHostName(location) {
+    if (!location.host) {
+      return location.href;
+    }
+    return location.protocol + "//" + location.host;
+  },
+
+  /**
+   * This method is overriden and left blank as for indexedDB, this operation
+   * cannot be performed synchronously. Thus, the preListStores method exists to
+   * do the same task asynchronously.
+   */
+  populateStoresForHosts() {},
+
+  getNamesForHost(host) {
+    let names = [];
+
+    for (let [dbName, {objectStores}] of this.hostVsStores.get(host)) {
+      if (objectStores.size) {
+        for (let objectStore of objectStores.keys()) {
+          names.push(JSON.stringify([dbName, objectStore]));
+        }
+      } else {
+        names.push(JSON.stringify([dbName]));
+      }
+    }
+    return names;
+  },
+
+  /**
+   * Returns the total number of entries for various types of requests to
+   * getStoreObjects for Indexed DB actor.
+   *
+   * @param {string} host
+   *        The host for the request.
+   * @param {array:string} names
+   *        Array of stringified name objects for indexed db actor.
+   *        The request type depends on the length of any parsed entry from this
+   *        array. 0 length refers to request for the whole host. 1 length
+   *        refers to request for a particular db in the host. 2 length refers
+   *        to a particular object store in a db in a host. 3 length refers to
+   *        particular items of an object store in a db in a host.
+   * @param {object} options
+   *        An options object containing following properties:
+   *         - index {string} The IDBIndex for the object store in the db.
+   */
+  getObjectsSize(host, names, options) {
+    // In Indexed DB, we are interested in only the first name, as the pattern
+    // should follow in all entries.
+    let name = names[0];
+    let parsedName = JSON.parse(name);
+
+    if (parsedName.length == 3) {
+      // This is the case where specific entries from an object store were
+      // requested
+      return names.length;
+    } else if (parsedName.length == 2) {
+      // This is the case where all entries from an object store are requested.
+      let index = options.index;
+      let [db, objectStore] = parsedName;
+      if (this.objectsSize[host + db + objectStore + index]) {
+        return this.objectsSize[host + db + objectStore + index];
+      }
+    } else if (parsedName.length == 1) {
+      // This is the case where details of all object stores in a db are
+      // requested.
+      if (this.hostVsStores.has(host) &&
+          this.hostVsStores.get(host).has(parsedName[0])) {
+        return this.hostVsStores.get(host).get(parsedName[0]).objectStores.size;
+      }
+    } else if (!parsedName || !parsedName.length) {
+      // This is the case were details of all dbs in a host are requested.
+      if (this.hostVsStores.has(host)) {
+        return this.hostVsStores.get(host).size;
+      }
+    }
+    return 0;
+  },
+
+  /**
+   * Purpose of this method is same as populateStoresForHosts but this is async.
+   * This exact same operation cannot be performed in populateStoresForHosts
+   * method, as that method is called in initialize method of the actor, which
+   * cannot be asynchronous.
+   */
+  preListStores: Task.async(function* () {
+    this.hostVsStores = new Map();
+
+    for (let host of this.hosts) {
+      yield this.populateStoresForHost(host);
+    }
+  }),
+
+  populateStoresForHost: Task.async(function* (host) {
+    let storeMap = new Map();
+    let {names} = yield this.getDBNamesForHost(host);
+    let win = this.storageActor.getWindowFromHost(host);
+    if (win) {
+      let principal = win.document.nodePrincipal;
+
+      for (let name of names) {
+        let metadata = yield this.getDBMetaData(host, principal, name);
+
+        metadata = indexedDBHelpers.patchMetadataMapsAndProtos(metadata);
+        storeMap.set(name, metadata);
+      }
+    }
+
+    this.hostVsStores.set(host, storeMap);
+  }),
+
+  /**
+   * Returns the over-the-wire implementation of the indexed db entity.
+   */
+  toStoreObject(item) {
+    if (!item) {
+      return null;
+    }
+
+    if ("indexes" in item) {
+      // Object store meta data
+      return {
+        objectStore: item.name,
+        keyPath: item.keyPath,
+        autoIncrement: item.autoIncrement,
+        indexes: item.indexes
+      };
+    }
+    if ("objectStores" in item) {
+      // DB meta data
+      return {
+        db: item.name,
+        origin: item.origin,
+        version: item.version,
+        objectStores: item.objectStores
+      };
+    }
+    // Indexed db entry
+    return {
+      name: item.name,
+      value: new LongStringActor(this.conn, JSON.stringify(item.value))
+    };
+  },
+
+  form(form, detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    let hosts = {};
+    for (let host of this.hosts) {
+      hosts[host] = this.getNamesForHost(host);
+    }
+
+    return {
+      actor: this.actorID,
+      hosts: hosts
+    };
+  },
+
+  onItemUpdated(action, host, path) {
+    // Database was removed, remove it from stores map
+    if (action === "deleted" && path.length === 1) {
+      if (this.hostVsStores.has(host)) {
+        this.hostVsStores.get(host).delete(path[0]);
+      }
+    }
+
+    this.storageActor.update(action, "indexedDB", {
+      [host]: [ JSON.stringify(path) ]
+    });
+  },
+
+  maybeSetupChildProcess() {
+    if (!DebuggerServer.isInChildProcess) {
+      this.backToChild = (func, rv) => rv;
+      this.getDBMetaData = indexedDBHelpers.getDBMetaData;
+      this.openWithPrincipal = indexedDBHelpers.openWithPrincipal;
+      this.getDBNamesForHost = indexedDBHelpers.getDBNamesForHost;
+      this.getSanitizedHost = indexedDBHelpers.getSanitizedHost;
+      this.getNameFromDatabaseFile = indexedDBHelpers.getNameFromDatabaseFile;
+      this.getValuesForHost = indexedDBHelpers.getValuesForHost;
+      this.getObjectStoreData = indexedDBHelpers.getObjectStoreData;
+      this.removeDB = indexedDBHelpers.removeDB;
+      this.removeDBRecord = indexedDBHelpers.removeDBRecord;
+      this.clearDBStore = indexedDBHelpers.clearDBStore;
+      return;
+    }
+
+    const { sendAsyncMessage, addMessageListener } =
+      this.conn.parentMessageManager;
+
+    this.conn.setupInParent({
+      module: "devtools/server/actors/storage",
+      setupParent: "setupParentProcessForIndexedDB"
+    });
+
+    this.getDBMetaData = callParentProcessAsync.bind(null, "getDBMetaData");
+    this.getDBNamesForHost = callParentProcessAsync.bind(null, "getDBNamesForHost");
+    this.getValuesForHost = callParentProcessAsync.bind(null, "getValuesForHost");
+    this.removeDB = callParentProcessAsync.bind(null, "removeDB");
+    this.removeDBRecord = callParentProcessAsync.bind(null, "removeDBRecord");
+    this.clearDBStore = callParentProcessAsync.bind(null, "clearDBStore");
+
+    addMessageListener("debug:storage-indexedDB-request-child", msg => {
+      switch (msg.json.method) {
+        case "backToChild": {
+          let [func, rv] = msg.json.args;
+          let deferred = unresolvedPromises.get(func);
+          if (deferred) {
+            unresolvedPromises.delete(func);
+            deferred.resolve(rv);
+          }
+          break;
+        }
+        case "onItemUpdated": {
+          let [action, host, path] = msg.json.args;
+          this.onItemUpdated(action, host, path);
+        }
+      }
+    });
+
+    let unresolvedPromises = new Map();
+    function callParentProcessAsync(methodName, ...args) {
+      let deferred = promise.defer();
+
+      unresolvedPromises.set(methodName, deferred);
+
+      sendAsyncMessage("debug:storage-indexedDB-request-parent", {
+        method: methodName,
+        args: args
+      });
+
+      return deferred.promise;
+    }
+  },
+
+  getFields: Task.async(function* (subType) {
+    switch (subType) {
+      // Detail of database
+      case "database":
+        return [
+          { name: "objectStore", editable: 0 },
+          { name: "keyPath", editable: 0 },
+          { name: "autoIncrement", editable: 0 },
+          { name: "indexes", editable: 0 },
+        ];
+
+      // Detail of object store
+      case "object store":
+        return [
+          { name: "name", editable: 0 },
+          { name: "value", editable: 0 }
+        ];
+
+      // Detail of indexedDB for one origin
+      default:
+        return [
+          { name: "db", editable: 0 },
+          { name: "origin", editable: 0 },
+          { name: "version", editable: 0 },
+          { name: "objectStores", editable: 0 },
+        ];
+    }
+  })
+});
+
+var indexedDBHelpers = {
+  backToChild(...args) {
+    let mm = Cc["@mozilla.org/globalmessagemanager;1"]
+               .getService(Ci.nsIMessageListenerManager);
+
+    mm.broadcastAsyncMessage("debug:storage-indexedDB-request-child", {
+      method: "backToChild",
+      args: args
+    });
+  },
+
+  onItemUpdated(action, host, path) {
+    let mm = Cc["@mozilla.org/globalmessagemanager;1"]
+               .getService(Ci.nsIMessageListenerManager);
+
+    mm.broadcastAsyncMessage("debug:storage-indexedDB-request-child", {
+      method: "onItemUpdated",
+      args: [ action, host, path ]
+    });
+  },
+
+  /**
+   * Fetches and stores all the metadata information for the given database
+   * `name` for the given `host` with its `principal`. The stored metadata
+   * information is of `DatabaseMetadata` type.
+   */
+  getDBMetaData: Task.async(function* (host, principal, name) {
+    let request = this.openWithPrincipal(principal, name);
+    let success = promise.defer();
+
+    request.onsuccess = event => {
+      let db = event.target.result;
+
+      let dbData = new DatabaseMetadata(host, db);
+      db.close();
+
+      success.resolve(this.backToChild("getDBMetaData", dbData));
+    };
+    request.onerror = ({target}) => {
+      console.error(
+        `Error opening indexeddb database ${name} for host ${host}`, target.error);
+      success.resolve(this.backToChild("getDBMetaData", null));
+    };
+    return success.promise;
+  }),
+
+  /**
+   * Opens an indexed db connection for the given `principal` and
+   * database `name`.
+   */
+  openWithPrincipal(principal, name) {
+    return indexedDBForStorage.openForPrincipal(principal, name);
+  },
+
+  removeDB: Task.async(function* (host, principal, name) {
+    let result = new promise(resolve => {
+      let request = indexedDBForStorage.deleteForPrincipal(principal, name);
+
+      request.onsuccess = () => {
+        resolve({});
+        this.onItemUpdated("deleted", host, [name]);
+      };
+
+      request.onblocked = () => {
+        console.warn(`Deleting indexedDB database ${name} for host ${host} is blocked`);
+        resolve({ blocked: true });
+      };
+
+      request.onerror = () => {
+        let { error } = request;
+        console.warn(
+          `Error deleting indexedDB database ${name} for host ${host}: ${error}`);
+        resolve({ error: error.message });
+      };
+
+      // If the database is blocked repeatedly, the onblocked event will not
+      // be fired again. To avoid waiting forever, report as blocked if nothing
+      // else happens after 3 seconds.
+      setTimeout(() => resolve({ blocked: true }), 3000);
+    });
+
+    return this.backToChild("removeDB", yield result);
+  }),
+
+  removeDBRecord: Task.async(function* (host, principal, dbName, storeName, id) {
+    let db;
+
+    try {
+      db = yield new promise((resolve, reject) => {
+        let request = this.openWithPrincipal(principal, dbName);
+        request.onsuccess = ev => resolve(ev.target.result);
+        request.onerror = ev => reject(ev.target.error);
+      });
+
+      let transaction = db.transaction(storeName, "readwrite");
+      let store = transaction.objectStore(storeName);
+
+      yield new promise((resolve, reject) => {
+        let request = store.delete(id);
+        request.onsuccess = () => resolve();
+        request.onerror = ev => reject(ev.target.error);
+      });
+
+      this.onItemUpdated("deleted", host, [dbName, storeName, id]);
+    } catch (error) {
+      let recordPath = [dbName, storeName, id].join("/");
+      console.error(`Failed to delete indexedDB record: ${recordPath}: ${error}`);
+    }
+
+    if (db) {
+      db.close();
+    }
+
+    return this.backToChild("removeDBRecord", null);
+  }),
+
+  clearDBStore: Task.async(function* (host, principal, dbName, storeName) {
+    let db;
+
+    try {
+      db = yield new promise((resolve, reject) => {
+        let request = this.openWithPrincipal(principal, dbName);
+        request.onsuccess = ev => resolve(ev.target.result);
+        request.onerror = ev => reject(ev.target.error);
+      });
+
+      let transaction = db.transaction(storeName, "readwrite");
+      let store = transaction.objectStore(storeName);
+
+      yield new promise((resolve, reject) => {
+        let request = store.clear();
+        request.onsuccess = () => resolve();
+        request.onerror = ev => reject(ev.target.error);
+      });
+
+      this.onItemUpdated("cleared", host, [dbName, storeName]);
+    } catch (error) {
+      let storePath = [dbName, storeName].join("/");
+      console.error(`Failed to clear indexedDB store: ${storePath}: ${error}`);
+    }
+
+    if (db) {
+      db.close();
+    }
+
+    return this.backToChild("clearDBStore", null);
+  }),
+
+  /**
+   * Fetches all the databases and their metadata for the given `host`.
+   */
+  getDBNamesForHost: Task.async(function* (host) {
+    let sanitizedHost = this.getSanitizedHost(host);
+    let directory = OS.Path.join(OS.Constants.Path.profileDir, "storage",
+                                 "default", sanitizedHost, "idb");
+
+    let exists = yield OS.File.exists(directory);
+    if (!exists && host.startsWith("about:")) {
+      // try for moz-safe-about directory
+      sanitizedHost = this.getSanitizedHost("moz-safe-" + host);
+      directory = OS.Path.join(OS.Constants.Path.profileDir, "storage",
+                               "permanent", sanitizedHost, "idb");
+      exists = yield OS.File.exists(directory);
+    }
+    if (!exists) {
+      return this.backToChild("getDBNamesForHost", {names: []});
+    }
+
+    let names = [];
+    let dirIterator = new OS.File.DirectoryIterator(directory);
+    try {
+      yield dirIterator.forEach(file => {
+        // Skip directories.
+        if (file.isDir) {
+          return null;
+        }
+
+        // Skip any non-sqlite files.
+        if (!file.name.endsWith(".sqlite")) {
+          return null;
+        }
+
+        return this.getNameFromDatabaseFile(file.path).then(name => {
+          if (name) {
+            names.push(name);
+          }
+          return null;
+        });
+      });
+    } finally {
+      dirIterator.close();
+    }
+    return this.backToChild("getDBNamesForHost", {names: names});
+  }),
+
+  /**
+   * Removes any illegal characters from the host name to make it a valid file
+   * name.
+   */
+  getSanitizedHost(host) {
+    return host.replace(ILLEGAL_CHAR_REGEX, "+");
+  },
+
+  /**
+   * Retrieves the proper indexed db database name from the provided .sqlite
+   * file location.
+   */
+  getNameFromDatabaseFile: Task.async(function* (path) {
+    let connection = null;
+    let retryCount = 0;
+
+    // Content pages might be having an open transaction for the same indexed db
+    // which this sqlite file belongs to. In that case, sqlite.openConnection
+    // will throw. Thus we retey for some time to see if lock is removed.
+    while (!connection && retryCount++ < 25) {
+      try {
+        connection = yield Sqlite.openConnection({ path: path });
+      } catch (ex) {
+        // Continuously retrying is overkill. Waiting for 100ms before next try
+        yield sleep(100);
+      }
+    }
+
+    if (!connection) {
+      return null;
+    }
+
+    let rows = yield connection.execute("SELECT name FROM database");
+    if (rows.length != 1) {
+      return null;
+    }
+
+    let name = rows[0].getResultByName("name");
+
+    yield connection.close();
+
+    return name;
+  }),
+
+  getValuesForHost: Task.async(function* (host, name = "null", options,
+                                          hostVsStores, principal) {
+    name = JSON.parse(name);
+    if (!name || !name.length) {
+      // This means that details about the db in this particular host are
+      // requested.
+      let dbs = [];
+      if (hostVsStores.has(host)) {
+        for (let [, db] of hostVsStores.get(host)) {
+          db = indexedDBHelpers.patchMetadataMapsAndProtos(db);
+          dbs.push(db.toObject());
+        }
+      }
+      return this.backToChild("getValuesForHost", {dbs: dbs});
+    }
+
+    let [db2, objectStore, id] = name;
+    if (!objectStore) {
+      // This means that details about all the object stores in this db are
+      // requested.
+      let objectStores = [];
+      if (hostVsStores.has(host) && hostVsStores.get(host).has(db2)) {
+        let db = hostVsStores.get(host).get(db2);
+
+        db = indexedDBHelpers.patchMetadataMapsAndProtos(db);
+
+        let objectStores2 = db.objectStores;
+
+        for (let objectStore2 of objectStores2) {
+          objectStores.push(objectStore2[1].toObject());
+        }
+      }
+      return this.backToChild("getValuesForHost", {objectStores: objectStores});
+    }
+    // Get either all entries from the object store, or a particular id
+    let result = yield this.getObjectStoreData(host, principal, db2,
+      objectStore, id, options.index, options.size);
+    return this.backToChild("getValuesForHost", {result: result});
+  }),
+
+  /**
+   * Returns all or requested entries from a particular objectStore from the db
+   * in the given host.
+   *
+   * @param {string} host
+   *        The given host.
+   * @param {nsIPrincipal} principal
+   *        The principal of the given document.
+   * @param {string} dbName
+   *        The name of the indexed db from the above host.
+   * @param {string} objectStore
+   *        The name of the object store from the above db.
+   * @param {string} id
+   *        id of the requested entry from the above object store.
+   *        null if all entries from the above object store are requested.
+   * @param {string} index
+   *        name of the IDBIndex to be iterated on while fetching entries.
+   *        null or "name" if no index is to be iterated.
+   * @param {number} offset
+   *        ofsset of the entries to be fetched.
+   * @param {number} size
+   *        The intended size of the entries to be fetched.
+   */
+  getObjectStoreData(host, principal, dbName, objectStore, id, index,
+                     offset, size) {
+    let request = this.openWithPrincipal(principal, dbName);
+    let success = promise.defer();
+    let data = [];
+    let db;
+
+    if (!size || size > MAX_STORE_OBJECT_COUNT) {
+      size = MAX_STORE_OBJECT_COUNT;
+    }
+
+    request.onsuccess = event => {
+      db = event.target.result;
+
+      let transaction = db.transaction(objectStore, "readonly");
+      let source = transaction.objectStore(objectStore);
+      if (index && index != "name") {
+        source = source.index(index);
+      }
+
+      source.count().onsuccess = event2 => {
+        let objectsSize = [];
+        let count = event2.target.result;
+        objectsSize.push({
+          key: host + dbName + objectStore + index,
+          count: count
+        });
+
+        if (!offset) {
+          offset = 0;
+        } else if (offset > count) {
+          db.close();
+          success.resolve([]);
+          return;
+        }
+
+        if (id) {
+          source.get(id).onsuccess = event3 => {
+            db.close();
+            success.resolve([{name: id, value: event3.target.result}]);
+          };
+        } else {
+          source.openCursor().onsuccess = event4 => {
+            let cursor = event4.target.result;
+
+            if (!cursor || data.length >= size) {
+              db.close();
+              success.resolve({
+                data: data,
+                objectsSize: objectsSize
+              });
+              return;
+            }
+            if (offset-- <= 0) {
+              data.push({name: cursor.key, value: cursor.value});
+            }
+            cursor.continue();
+          };
+        }
+      };
+    };
+    request.onerror = () => {
+      db.close();
+      success.resolve([]);
+    };
+    return success.promise;
+  },
+
+  /**
+   * When indexedDB metadata is parsed to and from JSON then the object's
+   * prototype is dropped and any Maps are changed to arrays of arrays. This
+   * method is used to repair the prototypes and fix any broken Maps.
+   */
+  patchMetadataMapsAndProtos(metadata) {
+    let md = Object.create(DatabaseMetadata.prototype);
+    Object.assign(md, metadata);
+
+    md._objectStores = new Map(metadata._objectStores);
+
+    for (let [name, store] of md._objectStores) {
+      let obj = Object.create(ObjectStoreMetadata.prototype);
+      Object.assign(obj, store);
+
+      md._objectStores.set(name, obj);
+
+      if (typeof store._indexes.length !== "undefined") {
+        obj._indexes = new Map(store._indexes);
+      }
+
+      for (let [name2, value] of obj._indexes) {
+        let obj2 = Object.create(IndexMetadata.prototype);
+        Object.assign(obj2, value);
+
+        obj._indexes.set(name2, obj2);
+      }
+    }
+
+    return md;
+  },
+
+  handleChildRequest(msg) {
+    let args = msg.data.args;
+
+    switch (msg.json.method) {
+      case "getDBMetaData": {
+        let [host, principal, name] = args;
+        return indexedDBHelpers.getDBMetaData(host, principal, name);
+      }
+      case "getDBNamesForHost": {
+        let [host] = args;
+        return indexedDBHelpers.getDBNamesForHost(host);
+      }
+      case "getValuesForHost": {
+        let [host, name, options, hostVsStores, principal] = args;
+        return indexedDBHelpers.getValuesForHost(host, name, options,
+                                                 hostVsStores, principal);
+      }
+      case "removeDB": {
+        let [host, principal, name] = args;
+        return indexedDBHelpers.removeDB(host, principal, name);
+      }
+      case "removeDBRecord": {
+        let [host, principal, db, store, id] = args;
+        return indexedDBHelpers.removeDBRecord(host, principal, db, store, id);
+      }
+      case "clearDBStore": {
+        let [host, principal, db, store] = args;
+        return indexedDBHelpers.clearDBStore(host, principal, db, store);
+      }
+      default:
+        console.error("ERR_DIRECTOR_PARENT_UNKNOWN_METHOD", msg.json.method);
+        throw new Error("ERR_DIRECTOR_PARENT_UNKNOWN_METHOD");
+    }
+  }
+};
+
+/**
+ * E10S parent/child setup helpers
+ */
+
+exports.setupParentProcessForIndexedDB = function ({ mm, prefix }) {
+  // listen for director-script requests from the child process
+  setMessageManager(mm);
+
+  function setMessageManager(newMM) {
+    if (mm) {
+      mm.removeMessageListener("debug:storage-indexedDB-request-parent",
+                               indexedDBHelpers.handleChildRequest);
+    }
+    mm = newMM;
+    if (mm) {
+      mm.addMessageListener("debug:storage-indexedDB-request-parent",
+                            indexedDBHelpers.handleChildRequest);
+    }
+  }
+
+  return {
+    onBrowserSwap: setMessageManager,
+    onDisconnected: () => setMessageManager(null),
+  };
+};
+
+/**
+ * The main Storage Actor.
+ */
+let StorageActor = protocol.ActorClassWithSpec(specs.storageSpec, {
+  typeName: "storage",
+
+  get window() {
+    return this.parentActor.window;
+  },
+
+  get document() {
+    return this.parentActor.window.document;
+  },
+
+  get windows() {
+    return this.childWindowPool;
+  },
+
+  initialize(conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this.conn = conn;
+    this.parentActor = tabActor;
+
+    this.childActorPool = new Map();
+    this.childWindowPool = new Set();
+
+    // Fetch all the inner iframe windows in this tab.
+    this.fetchChildWindows(this.parentActor.docShell);
+
+    // Initialize the registered store types
+    for (let [store, ActorConstructor] of storageTypePool) {
+      this.childActorPool.set(store, new ActorConstructor(this));
+    }
+
+    // Notifications that help us keep track of newly added windows and windows
+    // that got removed
+    Services.obs.addObserver(this, "content-document-global-created", false);
+    Services.obs.addObserver(this, "inner-window-destroyed", false);
+    this.onPageChange = this.onPageChange.bind(this);
+
+    let handler = tabActor.chromeEventHandler;
+    handler.addEventListener("pageshow", this.onPageChange, true);
+    handler.addEventListener("pagehide", this.onPageChange, true);
+
+    this.destroyed = false;
+    this.boundUpdate = {};
+  },
+
+  destroy() {
+    clearTimeout(this.batchTimer);
+    this.batchTimer = null;
+    // Remove observers
+    Services.obs.removeObserver(this, "content-document-global-created", false);
+    Services.obs.removeObserver(this, "inner-window-destroyed", false);
+    this.destroyed = true;
+    if (this.parentActor.browser) {
+      this.parentActor.browser.removeEventListener(
+        "pageshow", this.onPageChange, true);
+      this.parentActor.browser.removeEventListener(
+        "pagehide", this.onPageChange, true);
+    }
+    // Destroy the registered store types
+    for (let actor of this.childActorPool.values()) {
+      actor.destroy();
+    }
+    this.childActorPool.clear();
+    this.childWindowPool.clear();
+    this.childWindowPool = this.childActorPool = this.__poolMap = this.conn =
+      this.parentActor = this.boundUpdate = this.registeredPool =
+      this._pendingResponse = null;
+  },
+
+  /**
+   * Given a docshell, recursively find out all the child windows from it.
+   *
+   * @param {nsIDocShell} item
+   *        The docshell from which all inner windows need to be extracted.
+   */
+  fetchChildWindows(item) {
+    let docShell = item.QueryInterface(Ci.nsIDocShell)
+                       .QueryInterface(Ci.nsIDocShellTreeItem);
+    if (!docShell.contentViewer) {
+      return null;
+    }
+    let window = docShell.contentViewer.DOMDocument.defaultView;
+    if (window.location.href == "about:blank") {
+      // Skip out about:blank windows as Gecko creates them multiple times while
+      // creating any global.
+      return null;
+    }
+    this.childWindowPool.add(window);
+    for (let i = 0; i < docShell.childCount; i++) {
+      let child = docShell.getChildAt(i);
+      this.fetchChildWindows(child);
+    }
+    return null;
+  },
+
+  isIncludedInTopLevelWindow(window) {
+    return isWindowIncluded(this.window, window);
+  },
+
+  getWindowFromInnerWindowID(innerID) {
+    innerID = innerID.QueryInterface(Ci.nsISupportsPRUint64).data;
+    for (let win of this.childWindowPool.values()) {
+      let id = win.QueryInterface(Ci.nsIInterfaceRequestor)
+                   .getInterface(Ci.nsIDOMWindowUtils)
+                   .currentInnerWindowID;
+      if (id == innerID) {
+        return win;
+      }
+    }
+    return null;
+  },
+
+  getWindowFromHost(host) {
+    for (let win of this.childWindowPool.values()) {
+      let origin = win.document
+                      .nodePrincipal
+                      .originNoSuffix;
+      let url = win.document.URL;
+      if (origin === host || url === host) {
+        return win;
+      }
+    }
+    return null;
+  },
+
+  /**
+   * Event handler for any docshell update. This lets us figure out whenever
+   * any new window is added, or an existing window is removed.
+   */
+  observe(subject, topic) {
+    if (subject.location &&
+        (!subject.location.href || subject.location.href == "about:blank")) {
+      return null;
+    }
+
+    if (topic == "content-document-global-created" &&
+        this.isIncludedInTopLevelWindow(subject)) {
+      this.childWindowPool.add(subject);
+      events.emit(this, "window-ready", subject);
+    } else if (topic == "inner-window-destroyed") {
+      let window = this.getWindowFromInnerWindowID(subject);
+      if (window) {
+        this.childWindowPool.delete(window);
+        events.emit(this, "window-destroyed", window);
+      }
+    }
+    return null;
+  },
+
+  /**
+   * Called on "pageshow" or "pagehide" event on the chromeEventHandler of
+   * current tab.
+   *
+   * @param {event} The event object passed to the handler. We are using these
+   *        three properties from the event:
+   *         - target {document} The document corresponding to the event.
+   *         - type {string} Name of the event - "pageshow" or "pagehide".
+   *         - persisted {boolean} true if there was no
+   *                     "content-document-global-created" notification along
+   *                     this event.
+   */
+  onPageChange({target, type, persisted}) {
+    if (this.destroyed) {
+      return;
+    }
+
+    let window = target.defaultView;
+
+    if (type == "pagehide" && this.childWindowPool.delete(window)) {
+      events.emit(this, "window-destroyed", window);
+    } else if (type == "pageshow" && persisted && window.location.href &&
+               window.location.href != "about:blank" &&
+               this.isIncludedInTopLevelWindow(window)) {
+      this.childWindowPool.add(window);
+      events.emit(this, "window-ready", window);
+    }
+  },
+
+  /**
+   * Lists the available hosts for all the registered storage types.
+   *
+   * @returns {object} An object containing with the following structure:
+   *  - <storageType> : [{
+   *      actor: <actorId>,
+   *      host: <hostname>
+   *    }]
+   */
+  listStores: Task.async(function* () {
+    let toReturn = {};
+
+    for (let [name, value] of this.childActorPool) {
+      if (value.preListStores) {
+        yield value.preListStores();
+      }
+      toReturn[name] = value;
+    }
+
+    return toReturn;
+  }),
+
+  /**
+   * This method is called by the registered storage types so as to tell the
+   * Storage Actor that there are some changes in the stores. Storage Actor then
+   * notifies the client front about these changes at regular (BATCH_DELAY)
+   * interval.
+   *
+   * @param {string} action
+   *        The type of change. One of "added", "changed" or "deleted"
+   * @param {string} storeType
+   *        The storage actor in which this change has occurred.
+   * @param {object} data
+   *        The update object. This object is of the following format:
+   *         - {
+   *             <host1>: [<store_names1>, <store_name2>...],
+   *             <host2>: [<store_names34>...],
+   *           }
+   *           Where host1, host2 are the host in which this change happened and
+   *           [<store_namesX] is an array of the names of the changed store objects.
+   *           Pass an empty array if the host itself was affected: either completely
+   *           removed or cleared.
+   */
+  update(action, storeType, data) {
+    if (action == "cleared") {
+      events.emit(this, "stores-cleared", { [storeType]: data });
+      return null;
+    }
+
+    if (this.batchTimer) {
+      clearTimeout(this.batchTimer);
+    }
+    if (!this.boundUpdate[action]) {
+      this.boundUpdate[action] = {};
+    }
+    if (!this.boundUpdate[action][storeType]) {
+      this.boundUpdate[action][storeType] = {};
+    }
+    for (let host in data) {
+      if (!this.boundUpdate[action][storeType][host]) {
+        this.boundUpdate[action][storeType][host] = [];
+      }
+      for (let name of data[host]) {
+        if (!this.boundUpdate[action][storeType][host].includes(name)) {
+          this.boundUpdate[action][storeType][host].push(name);
+        }
+      }
+    }
+    if (action == "added") {
+      // If the same store name was previously deleted or changed, but now is
+      // added somehow, dont send the deleted or changed update.
+      this.removeNamesFromUpdateList("deleted", storeType, data);
+      this.removeNamesFromUpdateList("changed", storeType, data);
+    } else if (action == "changed" && this.boundUpdate.added &&
+             this.boundUpdate.added[storeType]) {
+      // If something got added and changed at the same time, then remove those
+      // items from changed instead.
+      this.removeNamesFromUpdateList("changed", storeType,
+                                     this.boundUpdate.added[storeType]);
+    } else if (action == "deleted") {
+      // If any item got delete, or a host got delete, no point in sending
+      // added or changed update
+      this.removeNamesFromUpdateList("added", storeType, data);
+      this.removeNamesFromUpdateList("changed", storeType, data);
+      for (let host in data) {
+        if (data[host].length == 0 && this.boundUpdate.added &&
+            this.boundUpdate.added[storeType] &&
+            this.boundUpdate.added[storeType][host]) {
+          delete this.boundUpdate.added[storeType][host];
+        }
+        if (data[host].length == 0 && this.boundUpdate.changed &&
+            this.boundUpdate.changed[storeType] &&
+            this.boundUpdate.changed[storeType][host]) {
+          delete this.boundUpdate.changed[storeType][host];
+        }
+      }
+    }
+
+    this.batchTimer = setTimeout(() => {
+      clearTimeout(this.batchTimer);
+      events.emit(this, "stores-update", this.boundUpdate);
+      this.boundUpdate = {};
+    }, BATCH_DELAY);
+
+    return null;
+  },
+
+  /**
+   * This method removes data from the this.boundUpdate object in the same
+   * manner like this.update() adds data to it.
+   *
+   * @param {string} action
+   *        The type of change. One of "added", "changed" or "deleted"
+   * @param {string} storeType
+   *        The storage actor for which you want to remove the updates data.
+   * @param {object} data
+   *        The update object. This object is of the following format:
+   *         - {
+   *             <host1>: [<store_names1>, <store_name2>...],
+   *             <host2>: [<store_names34>...],
+   *           }
+   *           Where host1, host2 are the hosts which you want to remove and
+   *           [<store_namesX] is an array of the names of the store objects.
+   */
+  removeNamesFromUpdateList(action, storeType, data) {
+    for (let host in data) {
+      if (this.boundUpdate[action] && this.boundUpdate[action][storeType] &&
+          this.boundUpdate[action][storeType][host]) {
+        for (let name in data[host]) {
+          let index = this.boundUpdate[action][storeType][host].indexOf(name);
+          if (index > -1) {
+            this.boundUpdate[action][storeType][host].splice(index, 1);
+          }
+        }
+        if (!this.boundUpdate[action][storeType][host].length) {
+          delete this.boundUpdate[action][storeType][host];
+        }
+      }
+    }
+    return null;
+  }
+});
+
+exports.StorageActor = StorageActor;
diff --git a/devtools/server/actors/string.js b/devtools/server/actors/string.js
new file mode 100644
index 000000000..d90a8b31c
--- /dev/null
+++ b/devtools/server/actors/string.js
@@ -0,0 +1,43 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var {DebuggerServer} = require("devtools/server/main");
+
+var promise = require("promise");
+
+var protocol = require("devtools/shared/protocol");
+const {longStringSpec} = require("devtools/shared/specs/string");
+
+exports.LongStringActor = protocol.ActorClassWithSpec(longStringSpec, {
+  initialize: function (conn, str) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.str = str;
+    this.short = (this.str.length < DebuggerServer.LONG_STRING_LENGTH);
+  },
+
+  destroy: function () {
+    this.str = null;
+    protocol.Actor.prototype.destroy.call(this);
+  },
+
+  form: function () {
+    if (this.short) {
+      return this.str;
+    }
+    return {
+      type: "longString",
+      actor: this.actorID,
+      length: this.str.length,
+      initial: this.str.substring(0, DebuggerServer.LONG_STRING_INITIAL_LENGTH)
+    };
+  },
+
+  substring: function (start, end) {
+    return promise.resolve(this.str.substring(start, end));
+  },
+
+  release: function () { }
+});
diff --git a/devtools/server/actors/styleeditor.js b/devtools/server/actors/styleeditor.js
new file mode 100644
index 000000000..5793a2baf
--- /dev/null
+++ b/devtools/server/actors/styleeditor.js
@@ -0,0 +1,528 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {Cc, Ci} = require("chrome");
+const Services = require("Services");
+const {XPCOMUtils} = require("resource://gre/modules/XPCOMUtils.jsm");
+const promise = require("promise");
+const events = require("sdk/event/core");
+const protocol = require("devtools/shared/protocol");
+const {Arg, method, RetVal} = protocol;
+const {fetch} = require("devtools/shared/DevToolsUtils");
+const {oldStyleSheetSpec, styleEditorSpec} = require("devtools/shared/specs/styleeditor");
+
+loader.lazyGetter(this, "CssLogic", () => require("devtools/shared/inspector/css-logic"));
+
+var TRANSITION_CLASS = "moz-styleeditor-transitioning";
+var TRANSITION_DURATION_MS = 500;
+var TRANSITION_RULE = "\
+:root.moz-styleeditor-transitioning, :root.moz-styleeditor-transitioning * {\
+transition-duration: " + TRANSITION_DURATION_MS + "ms !important; \
+transition-delay: 0ms !important;\
+transition-timing-function: ease-out !important;\
+transition-property: all !important;\
+}";
+
+var LOAD_ERROR = "error-load";
+
+var OldStyleSheetActor = protocol.ActorClassWithSpec(oldStyleSheetSpec, {
+  toString: function() {
+    return "[OldStyleSheetActor " + this.actorID + "]";
+  },
+
+  /**
+   * Window of target
+   */
+  get window() {
+    return this._window || this.parentActor.window;
+  },
+
+  /**
+   * Document of target.
+   */
+  get document() {
+    return this.window.document;
+  },
+
+  /**
+   * URL of underlying stylesheet.
+   */
+  get href() {
+    return this.rawSheet.href;
+  },
+
+  /**
+   * Retrieve the index (order) of stylesheet in the document.
+   *
+   * @return number
+   */
+  get styleSheetIndex()
+  {
+    if (this._styleSheetIndex == -1) {
+      for (let i = 0; i < this.document.styleSheets.length; i++) {
+        if (this.document.styleSheets[i] == this.rawSheet) {
+          this._styleSheetIndex = i;
+          break;
+        }
+      }
+    }
+    return this._styleSheetIndex;
+  },
+
+  initialize: function (aStyleSheet, aParentActor, aWindow) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this.rawSheet = aStyleSheet;
+    this.parentActor = aParentActor;
+    this.conn = this.parentActor.conn;
+
+    this._window = aWindow;
+
+    // text and index are unknown until source load
+    this.text = null;
+    this._styleSheetIndex = -1;
+
+    this._transitionRefCount = 0;
+
+    // if this sheet has an @import, then it's rules are loaded async
+    let ownerNode = this.rawSheet.ownerNode;
+    if (ownerNode) {
+      let onSheetLoaded = (event) => {
+        ownerNode.removeEventListener("load", onSheetLoaded, false);
+        this._notifyPropertyChanged("ruleCount");
+      };
+
+      ownerNode.addEventListener("load", onSheetLoaded, false);
+    }
+  },
+
+  /**
+   * Get the current state of the actor
+   *
+   * @return {object}
+   *         With properties of the underlying stylesheet, plus 'text',
+   *        'styleSheetIndex' and 'parentActor' if it's @imported
+   */
+  form: function (detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    let docHref;
+    if (this.rawSheet.ownerNode) {
+      if (this.rawSheet.ownerNode instanceof Ci.nsIDOMHTMLDocument) {
+        docHref = this.rawSheet.ownerNode.location.href;
+      }
+      if (this.rawSheet.ownerNode.ownerDocument) {
+        docHref = this.rawSheet.ownerNode.ownerDocument.location.href;
+      }
+    }
+
+    let form = {
+      actor: this.actorID,  // actorID is set when this actor is added to a pool
+      href: this.href,
+      nodeHref: docHref,
+      disabled: this.rawSheet.disabled,
+      title: this.rawSheet.title,
+      system: !CssLogic.isContentStylesheet(this.rawSheet),
+      styleSheetIndex: this.styleSheetIndex
+    };
+
+    try {
+      form.ruleCount = this.rawSheet.cssRules.length;
+    }
+    catch (e) {
+      // stylesheet had an @import rule that wasn't loaded yet
+    }
+    return form;
+  },
+
+  /**
+   * Toggle the disabled property of the style sheet
+   *
+   * @return {object}
+   *         'disabled' - the disabled state after toggling.
+   */
+  toggleDisabled: function () {
+    this.rawSheet.disabled = !this.rawSheet.disabled;
+    this._notifyPropertyChanged("disabled");
+
+    return this.rawSheet.disabled;
+  },
+
+  /**
+   * Send an event notifying that a property of the stylesheet
+   * has changed.
+   *
+   * @param  {string} property
+   *         Name of the changed property
+   */
+  _notifyPropertyChanged: function (property) {
+    events.emit(this, "property-change", property, this.form()[property]);
+  },
+
+   /**
+    * Fetch the source of the style sheet from its URL. Send a "sourceLoad"
+    * event when it's been fetched.
+    */
+  fetchSource: function () {
+    this._getText().then((content) => {
+      events.emit(this, "source-load", this.text);
+    });
+  },
+
+  /**
+   * Fetch the text for this stylesheet from the cache or network. Return
+   * cached text if it's already been fetched.
+   *
+   * @return {Promise}
+   *         Promise that resolves with a string text of the stylesheet.
+   */
+  _getText: function () {
+    if (this.text) {
+      return promise.resolve(this.text);
+    }
+
+    if (!this.href) {
+      // this is an inline <style> sheet
+      let content = this.rawSheet.ownerNode.textContent;
+      this.text = content;
+      return promise.resolve(content);
+    }
+
+    let options = {
+      policy: Ci.nsIContentPolicy.TYPE_INTERNAL_STYLESHEET,
+      window: this.window,
+      charset: this._getCSSCharset()
+    };
+
+    return fetch(this.href, options).then(({ content }) => {
+      this.text = content;
+      return content;
+    });
+  },
+
+  /**
+   * Get the charset of the stylesheet according to the character set rules
+   * defined in <http://www.w3.org/TR/CSS2/syndata.html#charset>.
+   * Note that some of the algorithm is implemented in DevToolsUtils.fetch.
+   */
+  _getCSSCharset: function ()
+  {
+    let sheet = this.rawSheet;
+    if (sheet) {
+      // Do we have a @charset rule in the stylesheet?
+      // step 2 of syndata.html (without the BOM check).
+      if (sheet.cssRules) {
+        let rules = sheet.cssRules;
+        if (rules.length
+            && rules.item(0).type == Ci.nsIDOMCSSRule.CHARSET_RULE) {
+          return rules.item(0).encoding;
+        }
+      }
+
+      // step 3: charset attribute of <link> or <style> element, if it exists
+      if (sheet.ownerNode && sheet.ownerNode.getAttribute) {
+        let linkCharset = sheet.ownerNode.getAttribute("charset");
+        if (linkCharset != null) {
+          return linkCharset;
+        }
+      }
+
+      // step 4 (1 of 2): charset of referring stylesheet.
+      let parentSheet = sheet.parentStyleSheet;
+      if (parentSheet && parentSheet.cssRules &&
+          parentSheet.cssRules[0].type == Ci.nsIDOMCSSRule.CHARSET_RULE) {
+        return parentSheet.cssRules[0].encoding;
+      }
+
+      // step 4 (2 of 2): charset of referring document.
+      if (sheet.ownerNode && sheet.ownerNode.ownerDocument.characterSet) {
+        return sheet.ownerNode.ownerDocument.characterSet;
+      }
+    }
+
+    // step 5: default to utf-8.
+    return "UTF-8";
+  },
+
+  /**
+   * Update the style sheet in place with new text.
+   *
+   * @param  {object} request
+   *         'text' - new text
+   *         'transition' - whether to do CSS transition for change.
+   */
+  update: function (text, transition) {
+    DOMUtils.parseStyleSheet(this.rawSheet, text);
+
+    this.text = text;
+
+    this._notifyPropertyChanged("ruleCount");
+
+    if (transition) {
+      this._insertTransistionRule();
+    }
+    else {
+      this._notifyStyleApplied();
+    }
+  },
+
+  /**
+   * Insert a catch-all transition rule into the document. Set a timeout
+   * to remove the rule after a certain time.
+   */
+  _insertTransistionRule: function () {
+    // Insert the global transition rule
+    // Use a ref count to make sure we do not add it multiple times.. and remove
+    // it only when all pending StyleEditor-generated transitions ended.
+    if (this._transitionRefCount == 0) {
+      this.rawSheet.insertRule(TRANSITION_RULE, this.rawSheet.cssRules.length);
+      this.document.documentElement.classList.add(TRANSITION_CLASS);
+    }
+
+    this._transitionRefCount++;
+
+    // Set up clean up and commit after transition duration (+10% buffer)
+    // @see _onTransitionEnd
+    this.window.setTimeout(this._onTransitionEnd.bind(this),
+                           Math.floor(TRANSITION_DURATION_MS * 1.1));
+  },
+
+  /**
+    * This cleans up class and rule added for transition effect and then
+    * notifies that the style has been applied.
+    */
+  _onTransitionEnd: function ()
+  {
+    if (--this._transitionRefCount == 0) {
+      this.document.documentElement.classList.remove(TRANSITION_CLASS);
+      this.rawSheet.deleteRule(this.rawSheet.cssRules.length - 1);
+    }
+
+    events.emit(this, "style-applied");
+  }
+});
+
+exports.OldStyleSheetActor = OldStyleSheetActor;
+
+/**
+ * Creates a StyleEditorActor. StyleEditorActor provides remote access to the
+ * stylesheets of a document.
+ */
+var StyleEditorActor = exports.StyleEditorActor = protocol.ActorClassWithSpec(styleEditorSpec, {
+  /**
+   * The window we work with, taken from the parent actor.
+   */
+  get window() {
+    return this.parentActor.window;
+  },
+
+  /**
+   * The current content document of the window we work with.
+   */
+  get document() {
+    return this.window.document;
+  },
+
+  form: function ()
+  {
+    return { actor: this.actorID };
+  },
+
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this.parentActor = tabActor;
+
+    // keep a map of sheets-to-actors so we don't create two actors for one sheet
+    this._sheets = new Map();
+  },
+
+  /**
+   * Destroy the current StyleEditorActor instance.
+   */
+  destroy: function ()
+  {
+    this._sheets.clear();
+  },
+
+  /**
+   * Called by client when target navigates to a new document.
+   * Adds load listeners to document.
+   */
+  newDocument: function () {
+    // delete previous document's actors
+    this._clearStyleSheetActors();
+
+    // Note: listening for load won't be necessary once
+    // https://bugzilla.mozilla.org/show_bug.cgi?id=839103 is fixed
+    if (this.document.readyState == "complete") {
+      this._onDocumentLoaded();
+    }
+    else {
+      this.window.addEventListener("load", this._onDocumentLoaded, false);
+    }
+    return {};
+  },
+
+  /**
+   * Event handler for document loaded event. Add actor for each stylesheet
+   * and send an event notifying of the load
+   */
+  _onDocumentLoaded: function (event) {
+    if (event) {
+      this.window.removeEventListener("load", this._onDocumentLoaded, false);
+    }
+
+    let documents = [this.document];
+    var forms = [];
+    for (let doc of documents) {
+      let sheetForms = this._addStyleSheets(doc.styleSheets);
+      forms = forms.concat(sheetForms);
+      // Recursively handle style sheets of the documents in iframes.
+      for (let iframe of doc.getElementsByTagName("iframe")) {
+        documents.push(iframe.contentDocument);
+      }
+    }
+
+    events.emit(this, "document-load", forms);
+  },
+
+  /**
+   * Add all the stylesheets to the map and create an actor for each one
+   * if not already created. Send event that there are new stylesheets.
+   *
+   * @param {[DOMStyleSheet]} styleSheets
+   *        Stylesheets to add
+   * @return {[object]}
+   *         Array of actors for each StyleSheetActor created
+   */
+  _addStyleSheets: function (styleSheets)
+  {
+    let sheets = [];
+    for (let i = 0; i < styleSheets.length; i++) {
+      let styleSheet = styleSheets[i];
+      sheets.push(styleSheet);
+
+      // Get all sheets, including imported ones
+      let imports = this._getImported(styleSheet);
+      sheets = sheets.concat(imports);
+    }
+    let actors = sheets.map(this._createStyleSheetActor.bind(this));
+
+    return actors;
+  },
+
+  /**
+   * Create a new actor for a style sheet, if it hasn't already been created.
+   *
+   * @param  {DOMStyleSheet} styleSheet
+   *         The style sheet to create an actor for.
+   * @return {StyleSheetActor}
+   *         The actor for this style sheet
+   */
+  _createStyleSheetActor: function (styleSheet)
+  {
+    if (this._sheets.has(styleSheet)) {
+      return this._sheets.get(styleSheet);
+    }
+    let actor = new OldStyleSheetActor(styleSheet, this);
+
+    this.manage(actor);
+    this._sheets.set(styleSheet, actor);
+
+    return actor;
+  },
+
+  /**
+   * Get all the stylesheets @imported from a stylesheet.
+   *
+   * @param  {DOMStyleSheet} styleSheet
+   *         Style sheet to search
+   * @return {array}
+   *         All the imported stylesheets
+   */
+  _getImported: function (styleSheet) {
+   let imported = [];
+
+   for (let i = 0; i < styleSheet.cssRules.length; i++) {
+      let rule = styleSheet.cssRules[i];
+      if (rule.type == Ci.nsIDOMCSSRule.IMPORT_RULE) {
+        // Associated styleSheet may be null if it has already been seen due to
+        // duplicate @imports for the same URL.
+        if (!rule.styleSheet) {
+          continue;
+        }
+        imported.push(rule.styleSheet);
+
+        // recurse imports in this stylesheet as well
+        imported = imported.concat(this._getImported(rule.styleSheet));
+      }
+      else if (rule.type != Ci.nsIDOMCSSRule.CHARSET_RULE) {
+        // @import rules must precede all others except @charset
+        break;
+      }
+    }
+    return imported;
+  },
+
+  /**
+   * Clear all the current stylesheet actors in map.
+   */
+  _clearStyleSheetActors: function () {
+    for (let actor in this._sheets) {
+      this.unmanage(this._sheets[actor]);
+    }
+    this._sheets.clear();
+  },
+
+  /**
+   * Create a new style sheet in the document with the given text.
+   * Return an actor for it.
+   *
+   * @param  {object} request
+   *         Debugging protocol request object, with 'text property'
+   * @return {object}
+   *         Object with 'styelSheet' property for form on new actor.
+   */
+  newStyleSheet: function (text) {
+    let parent = this.document.documentElement;
+    let style = this.document.createElementNS("http://www.w3.org/1999/xhtml", "style");
+    style.setAttribute("type", "text/css");
+
+    if (text) {
+      style.appendChild(this.document.createTextNode(text));
+    }
+    parent.appendChild(style);
+
+    let actor = this._createStyleSheetActor(style.sheet);
+    return actor;
+  }
+});
+
+XPCOMUtils.defineLazyGetter(this, "DOMUtils", function () {
+  return Cc["@mozilla.org/inspector/dom-utils;1"].getService(Ci.inIDOMUtils);
+});
+
+exports.StyleEditorActor = StyleEditorActor;
+
+/**
+ * Normalize multiple relative paths towards the base paths on the right.
+ */
+function normalize(...aURLs) {
+  let base = Services.io.newURI(aURLs.pop(), null, null);
+  let url;
+  while ((url = aURLs.pop())) {
+    base = Services.io.newURI(url, null, base);
+  }
+  return base.spec;
+}
+
+function dirname(aPath) {
+  return Services.io.newURI(
+    ".", null, Services.io.newURI(aPath, null, null)).spec;
+}
diff --git a/devtools/server/actors/styles.js b/devtools/server/actors/styles.js
new file mode 100644
index 000000000..cdb812882
--- /dev/null
+++ b/devtools/server/actors/styles.js
@@ -0,0 +1,1687 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {Cc, Ci} = require("chrome");
+const promise = require("promise");
+const protocol = require("devtools/shared/protocol");
+const {LongStringActor} = require("devtools/server/actors/string");
+const {getDefinedGeometryProperties} = require("devtools/server/actors/highlighters/geometry-editor");
+const {parseDeclarations} = require("devtools/shared/css/parsing-utils");
+const {isCssPropertyKnown} = require("devtools/server/actors/css-properties");
+const {Task} = require("devtools/shared/task");
+const events = require("sdk/event/core");
+
+// This will also add the "stylesheet" actor type for protocol.js to recognize
+const {UPDATE_PRESERVING_RULES, UPDATE_GENERAL} = require("devtools/server/actors/stylesheets");
+const {pageStyleSpec, styleRuleSpec, ELEMENT_STYLE} = require("devtools/shared/specs/styles");
+
+loader.lazyGetter(this, "CssLogic", () => require("devtools/server/css-logic").CssLogic);
+loader.lazyGetter(this, "SharedCssLogic", () => require("devtools/shared/inspector/css-logic"));
+loader.lazyGetter(this, "DOMUtils", () => Cc["@mozilla.org/inspector/dom-utils;1"].getService(Ci.inIDOMUtils));
+
+loader.lazyGetter(this, "PSEUDO_ELEMENTS", () => {
+  return DOMUtils.getCSSPseudoElementNames();
+});
+
+const XHTML_NS = "http://www.w3.org/1999/xhtml";
+const FONT_PREVIEW_TEXT = "Abc";
+const FONT_PREVIEW_FONT_SIZE = 40;
+const FONT_PREVIEW_FILLSTYLE = "black";
+const NORMAL_FONT_WEIGHT = 400;
+const BOLD_FONT_WEIGHT = 700;
+// Offset (in px) to avoid cutting off text edges of italic fonts.
+const FONT_PREVIEW_OFFSET = 4;
+
+/**
+ * The PageStyle actor lets the client look at the styles on a page, as
+ * they are applied to a given node.
+ */
+var PageStyleActor = protocol.ActorClassWithSpec(pageStyleSpec, {
+  /**
+   * Create a PageStyleActor.
+   *
+   * @param inspector
+   *    The InspectorActor that owns this PageStyleActor.
+   *
+   * @constructor
+   */
+  initialize: function (inspector) {
+    protocol.Actor.prototype.initialize.call(this, null);
+    this.inspector = inspector;
+    if (!this.inspector.walker) {
+      throw Error("The inspector's WalkerActor must be created before " +
+                   "creating a PageStyleActor.");
+    }
+    this.walker = inspector.walker;
+    this.cssLogic = new CssLogic(DOMUtils.isInheritedProperty);
+
+    // Stores the association of DOM objects -> actors
+    this.refMap = new Map();
+
+    // Maps document elements to style elements, used to add new rules.
+    this.styleElements = new WeakMap();
+
+    this.onFrameUnload = this.onFrameUnload.bind(this);
+    this.onStyleSheetAdded = this.onStyleSheetAdded.bind(this);
+
+    events.on(this.inspector.tabActor, "will-navigate", this.onFrameUnload);
+    events.on(this.inspector.tabActor, "stylesheet-added", this.onStyleSheetAdded);
+
+    this._styleApplied = this._styleApplied.bind(this);
+    this._watchedSheets = new Set();
+  },
+
+  destroy: function () {
+    if (!this.walker) {
+      return;
+    }
+    protocol.Actor.prototype.destroy.call(this);
+    events.off(this.inspector.tabActor, "will-navigate", this.onFrameUnload);
+    events.off(this.inspector.tabActor, "stylesheet-added", this.onStyleSheetAdded);
+    this.inspector = null;
+    this.walker = null;
+    this.refMap = null;
+    this.cssLogic = null;
+    this.styleElements = null;
+
+    for (let sheet of this._watchedSheets) {
+      sheet.off("style-applied", this._styleApplied);
+    }
+    this._watchedSheets.clear();
+  },
+
+  get conn() {
+    return this.inspector.conn;
+  },
+
+  form: function (detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    return {
+      actor: this.actorID,
+      traits: {
+        // Whether the actor has had bug 1103993 fixed, which means that the
+        // getApplied method calls cssLogic.highlight(node) to recreate the
+        // style cache. Clients requesting getApplied from actors that have not
+        // been fixed must make sure cssLogic.highlight(node) was called before.
+        getAppliedCreatesStyleCache: true,
+        // Whether addNewRule accepts the editAuthored argument.
+        authoredStyles: true
+      }
+    };
+  },
+
+  /**
+   * Called when a style sheet is updated.
+   */
+  _styleApplied: function (kind, styleSheet) {
+    // No matter what kind of update is done, we need to invalidate
+    // the keyframe cache.
+    this.cssLogic.reset();
+    if (kind === UPDATE_GENERAL) {
+      events.emit(this, "stylesheet-updated", styleSheet);
+    }
+  },
+
+  /**
+   * Return or create a StyleRuleActor for the given item.
+   * @param item Either a CSSStyleRule or a DOM element.
+   */
+  _styleRef: function (item) {
+    if (this.refMap.has(item)) {
+      return this.refMap.get(item);
+    }
+    let actor = StyleRuleActor(this, item);
+    this.manage(actor);
+    this.refMap.set(item, actor);
+
+    return actor;
+  },
+
+  /**
+   * Update the association between a StyleRuleActor and its
+   * corresponding item.  This is used when a StyleRuleActor updates
+   * as style sheet and starts using a new rule.
+   *
+   * @param oldItem The old association; either a CSSStyleRule or a
+   *                DOM element.
+   * @param item Either a CSSStyleRule or a DOM element.
+   * @param actor a StyleRuleActor
+   */
+  updateStyleRef: function (oldItem, item, actor) {
+    this.refMap.delete(oldItem);
+    this.refMap.set(item, actor);
+  },
+
+  /**
+   * Return or create a StyleSheetActor for the given nsIDOMCSSStyleSheet.
+   * @param  {DOMStyleSheet} sheet
+   *         The style sheet to create an actor for.
+   * @return {StyleSheetActor}
+   *         The actor for this style sheet
+   */
+  _sheetRef: function (sheet) {
+    let tabActor = this.inspector.tabActor;
+    let actor = tabActor.createStyleSheetActor(sheet);
+    return actor;
+  },
+
+  /**
+   * Get the computed style for a node.
+   *
+   * @param NodeActor node
+   * @param object options
+   *   `filter`: A string filter that affects the "matched" handling.
+   *     'user': Include properties from user style sheets.
+   *     'ua': Include properties from user and user-agent sheets.
+   *     Default value is 'ua'
+   *   `markMatched`: true if you want the 'matched' property to be added
+   *     when a computed property has been modified by a style included
+   *     by `filter`.
+   *   `onlyMatched`: true if unmatched properties shouldn't be included.
+   *
+   * @returns a JSON blob with the following form:
+   *   {
+   *     "property-name": {
+   *       value: "property-value",
+   *       priority: "!important" <optional>
+   *       matched: <true if there are matched selectors for this value>
+   *     },
+   *     ...
+   *   }
+   */
+  getComputed: function (node, options) {
+    let ret = Object.create(null);
+
+    this.cssLogic.sourceFilter = options.filter || SharedCssLogic.FILTER.UA;
+    this.cssLogic.highlight(node.rawNode);
+    let computed = this.cssLogic.computedStyle || [];
+
+    Array.prototype.forEach.call(computed, name => {
+      ret[name] = {
+        value: computed.getPropertyValue(name),
+        priority: computed.getPropertyPriority(name) || undefined
+      };
+    });
+
+    if (options.markMatched || options.onlyMatched) {
+      let matched = this.cssLogic.hasMatchedSelectors(Object.keys(ret));
+      for (let key in ret) {
+        if (matched[key]) {
+          ret[key].matched = options.markMatched ? true : undefined;
+        } else if (options.onlyMatched) {
+          delete ret[key];
+        }
+      }
+    }
+
+    return ret;
+  },
+
+  /**
+   * Get all the fonts from a page.
+   *
+   * @param object options
+   *   `includePreviews`: Whether to also return image previews of the fonts.
+   *   `previewText`: The text to display in the previews.
+   *   `previewFontSize`: The font size of the text in the previews.
+   *
+   * @returns object
+   *   object with 'fontFaces', a list of fonts that apply to this node.
+   */
+  getAllUsedFontFaces: function (options) {
+    let windows = this.inspector.tabActor.windows;
+    let fontsList = [];
+    for (let win of windows) {
+      fontsList = [...fontsList,
+                   ...this.getUsedFontFaces(win.document.body, options)];
+    }
+    return fontsList;
+  },
+
+  /**
+   * Get the font faces used in an element.
+   *
+   * @param NodeActor node / actual DOM node
+   *    The node to get fonts from.
+   * @param object options
+   *   `includePreviews`: Whether to also return image previews of the fonts.
+   *   `previewText`: The text to display in the previews.
+   *   `previewFontSize`: The font size of the text in the previews.
+   *
+   * @returns object
+   *   object with 'fontFaces', a list of fonts that apply to this node.
+   */
+  getUsedFontFaces: function (node, options) {
+    // node.rawNode is defined for NodeActor objects
+    let actualNode = node.rawNode || node;
+    let contentDocument = actualNode.ownerDocument;
+    // We don't get fonts for a node, but for a range
+    let rng = contentDocument.createRange();
+    rng.selectNodeContents(actualNode);
+    let fonts = DOMUtils.getUsedFontFaces(rng);
+    let fontsArray = [];
+
+    for (let i = 0; i < fonts.length; i++) {
+      let font = fonts.item(i);
+      let fontFace = {
+        name: font.name,
+        CSSFamilyName: font.CSSFamilyName,
+        srcIndex: font.srcIndex,
+        URI: font.URI,
+        format: font.format,
+        localName: font.localName,
+        metadata: font.metadata
+      };
+
+      // If this font comes from a @font-face rule
+      if (font.rule) {
+        let styleActor = StyleRuleActor(this, font.rule);
+        this.manage(styleActor);
+        fontFace.rule = styleActor;
+        fontFace.ruleText = font.rule.cssText;
+      }
+
+      // Get the weight and style of this font for the preview and sort order
+      let weight = NORMAL_FONT_WEIGHT, style = "";
+      if (font.rule) {
+        weight = font.rule.style.getPropertyValue("font-weight")
+                 || NORMAL_FONT_WEIGHT;
+        if (weight == "bold") {
+          weight = BOLD_FONT_WEIGHT;
+        } else if (weight == "normal") {
+          weight = NORMAL_FONT_WEIGHT;
+        }
+        style = font.rule.style.getPropertyValue("font-style") || "";
+      }
+      fontFace.weight = weight;
+      fontFace.style = style;
+
+      if (options.includePreviews) {
+        let opts = {
+          previewText: options.previewText,
+          previewFontSize: options.previewFontSize,
+          fontStyle: weight + " " + style,
+          fillStyle: options.previewFillStyle
+        };
+        let { dataURL, size } = getFontPreviewData(font.CSSFamilyName,
+                                                   contentDocument, opts);
+        fontFace.preview = {
+          data: LongStringActor(this.conn, dataURL),
+          size: size
+        };
+      }
+      fontsArray.push(fontFace);
+    }
+
+    // @font-face fonts at the top, then alphabetically, then by weight
+    fontsArray.sort(function (a, b) {
+      return a.weight > b.weight ? 1 : -1;
+    });
+    fontsArray.sort(function (a, b) {
+      if (a.CSSFamilyName == b.CSSFamilyName) {
+        return 0;
+      }
+      return a.CSSFamilyName > b.CSSFamilyName ? 1 : -1;
+    });
+    fontsArray.sort(function (a, b) {
+      if ((a.rule && b.rule) || (!a.rule && !b.rule)) {
+        return 0;
+      }
+      return !a.rule && b.rule ? 1 : -1;
+    });
+
+    return fontsArray;
+  },
+
+  /**
+   * Get a list of selectors that match a given property for a node.
+   *
+   * @param NodeActor node
+   * @param string property
+   * @param object options
+   *   `filter`: A string filter that affects the "matched" handling.
+   *     'user': Include properties from user style sheets.
+   *     'ua': Include properties from user and user-agent sheets.
+   *     Default value is 'ua'
+   *
+   * @returns a JSON object with the following form:
+   *   {
+   *     // An ordered list of rules that apply
+   *     matched: [{
+   *       rule: <rule actorid>,
+   *       sourceText: <string>, // The source of the selector, relative
+   *                             // to the node in question.
+   *       selector: <string>, // the selector ID that matched
+   *       value: <string>, // the value of the property
+   *       status: <int>,
+   *         // The status of the match - high numbers are better placed
+   *         // to provide styling information:
+   *         // 3: Best match, was used.
+   *         // 2: Matched, but was overridden.
+   *         // 1: Rule from a parent matched.
+   *         // 0: Unmatched (never returned in this API)
+   *     }, ...],
+   *
+   *     // The full form of any domrule referenced.
+   *     rules: [ <domrule>, ... ], // The full form of any domrule referenced
+   *
+   *     // The full form of any sheets referenced.
+   *     sheets: [ <domsheet>, ... ]
+   *  }
+   */
+  getMatchedSelectors: function (node, property, options) {
+    this.cssLogic.sourceFilter = options.filter || SharedCssLogic.FILTER.UA;
+    this.cssLogic.highlight(node.rawNode);
+
+    let rules = new Set();
+    let sheets = new Set();
+
+    let matched = [];
+    let propInfo = this.cssLogic.getPropertyInfo(property);
+    for (let selectorInfo of propInfo.matchedSelectors) {
+      let cssRule = selectorInfo.selector.cssRule;
+      let domRule = cssRule.sourceElement || cssRule.domRule;
+
+      let rule = this._styleRef(domRule);
+      rules.add(rule);
+
+      matched.push({
+        rule: rule,
+        sourceText: this.getSelectorSource(selectorInfo, node.rawNode),
+        selector: selectorInfo.selector.text,
+        name: selectorInfo.property,
+        value: selectorInfo.value,
+        status: selectorInfo.status
+      });
+    }
+
+    this.expandSets(rules, sheets);
+
+    return {
+      matched: matched,
+      rules: [...rules],
+      sheets: [...sheets]
+    };
+  },
+
+  // Get a selector source for a CssSelectorInfo relative to a given
+  // node.
+  getSelectorSource: function (selectorInfo, relativeTo) {
+    let result = selectorInfo.selector.text;
+    if (selectorInfo.elementStyle) {
+      let source = selectorInfo.sourceElement;
+      if (source === relativeTo) {
+        result = "this";
+      } else {
+        result = CssLogic.getShortName(source);
+      }
+      result += ".style";
+    }
+    return result;
+  },
+
+  /**
+   * Get the set of styles that apply to a given node.
+   * @param NodeActor node
+   * @param object options
+   *   `filter`: A string filter that affects the "matched" handling.
+   *     'user': Include properties from user style sheets.
+   *     'ua': Include properties from user and user-agent sheets.
+   *     Default value is 'ua'
+   *   `inherited`: Include styles inherited from parent nodes.
+   *   `matchedSelectors`: Include an array of specific selectors that
+   *     caused this rule to match its node.
+   */
+  getApplied: Task.async(function* (node, options) {
+    if (!node) {
+      return {entries: [], rules: [], sheets: []};
+    }
+
+    this.cssLogic.highlight(node.rawNode);
+    let entries = [];
+    entries = entries.concat(this._getAllElementRules(node, undefined,
+                                                      options));
+
+    let result = this.getAppliedProps(node, entries, options);
+    for (let rule of result.rules) {
+      // See the comment in |form| to understand this.
+      yield rule.getAuthoredCssText();
+    }
+    return result;
+  }),
+
+  _hasInheritedProps: function (style) {
+    return Array.prototype.some.call(style, prop => {
+      return DOMUtils.isInheritedProperty(prop);
+    });
+  },
+
+  isPositionEditable: Task.async(function* (node) {
+    if (!node || node.rawNode.nodeType !== node.rawNode.ELEMENT_NODE) {
+      return false;
+    }
+
+    let props = getDefinedGeometryProperties(node.rawNode);
+
+    // Elements with only `width` and `height` are currently not considered
+    // editable.
+    return props.has("top") ||
+           props.has("right") ||
+           props.has("left") ||
+           props.has("bottom");
+  }),
+
+  /**
+   * Helper function for getApplied, gets all the rules from a given
+   * element. See getApplied for documentation on parameters.
+   * @param NodeActor node
+   * @param bool inherited
+   * @param object options
+
+   * @return Array The rules for a given element. Each item in the
+   *               array has the following signature:
+   *                - rule RuleActor
+   *                - isSystem Boolean
+   *                - inherited Boolean
+   *                - pseudoElement String
+   */
+  _getAllElementRules: function (node, inherited, options) {
+    let {bindingElement, pseudo} =
+        CssLogic.getBindingElementAndPseudo(node.rawNode);
+    let rules = [];
+
+    if (!bindingElement || !bindingElement.style) {
+      return rules;
+    }
+
+    let elementStyle = this._styleRef(bindingElement);
+    let showElementStyles = !inherited && !pseudo;
+    let showInheritedStyles = inherited &&
+                              this._hasInheritedProps(bindingElement.style);
+
+    let rule = {
+      rule: elementStyle,
+      pseudoElement: null,
+      isSystem: false,
+      inherited: false
+    };
+
+    // First any inline styles
+    if (showElementStyles) {
+      rules.push(rule);
+    }
+
+    // Now any inherited styles
+    if (showInheritedStyles) {
+      rule.inherited = inherited;
+      rules.push(rule);
+    }
+
+    // Add normal rules.  Typically this is passing in the node passed into the
+    // function, unless if that node was ::before/::after.  In which case,
+    // it will pass in the parentNode along with "::before"/"::after".
+    this._getElementRules(bindingElement, pseudo, inherited, options)
+        .forEach(oneRule => {
+          // The only case when there would be a pseudo here is
+          // ::before/::after, and in this case we want to tell the
+          // view that it belongs to the element (which is a
+          // _moz_generated_content native anonymous element).
+          oneRule.pseudoElement = null;
+          rules.push(oneRule);
+        });
+
+    // Now any pseudos.
+    if (showElementStyles) {
+      for (let readPseudo of PSEUDO_ELEMENTS) {
+        this._getElementRules(bindingElement, readPseudo, inherited, options)
+            .forEach(oneRule => {
+              rules.push(oneRule);
+            });
+      }
+    }
+
+    return rules;
+  },
+
+  /**
+   * Helper function for _getAllElementRules, returns the rules from a given
+   * element. See getApplied for documentation on parameters.
+   * @param DOMNode node
+   * @param string pseudo
+   * @param DOMNode inherited
+   * @param object options
+   *
+   * @returns Array
+   */
+  _getElementRules: function (node, pseudo, inherited, options) {
+    let domRules = DOMUtils.getCSSStyleRules(node, pseudo);
+    if (!domRules) {
+      return [];
+    }
+
+    let rules = [];
+
+    // getCSSStyleRules returns ordered from least-specific to
+    // most-specific.
+    for (let i = domRules.Count() - 1; i >= 0; i--) {
+      let domRule = domRules.GetElementAt(i);
+
+      let isSystem = !SharedCssLogic.isContentStylesheet(domRule.parentStyleSheet);
+
+      if (isSystem && options.filter != SharedCssLogic.FILTER.UA) {
+        continue;
+      }
+
+      if (inherited) {
+        // Don't include inherited rules if none of its properties
+        // are inheritable.
+        let hasInherited = [...domRule.style].some(
+          prop => DOMUtils.isInheritedProperty(prop)
+        );
+        if (!hasInherited) {
+          continue;
+        }
+      }
+
+      let ruleActor = this._styleRef(domRule);
+      rules.push({
+        rule: ruleActor,
+        inherited: inherited,
+        isSystem: isSystem,
+        pseudoElement: pseudo
+      });
+    }
+    return rules;
+  },
+
+  /**
+   * Given a node and a CSS rule, walk up the DOM looking for a
+   * matching element rule.  Return an array of all found entries, in
+   * the form generated by _getAllElementRules.  Note that this will
+   * always return an array of either zero or one element.
+   *
+   * @param {NodeActor} node the node
+   * @param {CSSStyleRule} filterRule the rule to filter for
+   * @return {Array} array of zero or one elements; if one, the element
+   *                 is the entry as returned by _getAllElementRules.
+   */
+  findEntryMatchingRule: function (node, filterRule) {
+    const options = {matchedSelectors: true, inherited: true};
+    let entries = [];
+    let parent = this.walker.parentNode(node);
+    while (parent && parent.rawNode.nodeType != Ci.nsIDOMNode.DOCUMENT_NODE) {
+      entries = entries.concat(this._getAllElementRules(parent, parent,
+                                                        options));
+      parent = this.walker.parentNode(parent);
+    }
+
+    return entries.filter(entry => entry.rule.rawRule === filterRule);
+  },
+
+  /**
+   * Helper function for getApplied that fetches a set of style properties that
+   * apply to the given node and associated rules
+   * @param NodeActor node
+   * @param object options
+   *   `filter`: A string filter that affects the "matched" handling.
+   *     'user': Include properties from user style sheets.
+   *     'ua': Include properties from user and user-agent sheets.
+   *     Default value is 'ua'
+   *   `inherited`: Include styles inherited from parent nodes.
+   *   `matchedSelectors`: Include an array of specific selectors that
+   *     caused this rule to match its node.
+   * @param array entries
+   *   List of appliedstyle objects that lists the rules that apply to the
+   *   node. If adding a new rule to the stylesheet, only the new rule entry
+   *   is provided and only the style properties that apply to the new
+   *   rule is fetched.
+   * @returns Object containing the list of rule entries, rule actors and
+   *   stylesheet actors that applies to the given node and its associated
+   *   rules.
+   */
+  getAppliedProps: function (node, entries, options) {
+    if (options.inherited) {
+      let parent = this.walker.parentNode(node);
+      while (parent && parent.rawNode.nodeType != Ci.nsIDOMNode.DOCUMENT_NODE) {
+        entries = entries.concat(this._getAllElementRules(parent, parent,
+                                                          options));
+        parent = this.walker.parentNode(parent);
+      }
+    }
+
+    if (options.matchedSelectors) {
+      for (let entry of entries) {
+        if (entry.rule.type === ELEMENT_STYLE) {
+          continue;
+        }
+
+        let domRule = entry.rule.rawRule;
+        let selectors = CssLogic.getSelectors(domRule);
+        let element = entry.inherited ? entry.inherited.rawNode : node.rawNode;
+
+        let {bindingElement, pseudo} =
+            CssLogic.getBindingElementAndPseudo(element);
+        entry.matchedSelectors = [];
+        for (let i = 0; i < selectors.length; i++) {
+          if (DOMUtils.selectorMatchesElement(bindingElement, domRule, i,
+                                              pseudo)) {
+            entry.matchedSelectors.push(selectors[i]);
+          }
+        }
+      }
+    }
+
+    // Add all the keyframes rule associated with the element
+    let computedStyle = this.cssLogic.computedStyle;
+    if (computedStyle) {
+      let animationNames = computedStyle.animationName.split(",");
+      animationNames = animationNames.map(name => name.trim());
+
+      if (animationNames) {
+        // Traverse through all the available keyframes rule and add
+        // the keyframes rule that matches the computed animation name
+        for (let keyframesRule of this.cssLogic.keyframesRules) {
+          if (animationNames.indexOf(keyframesRule.name) > -1) {
+            for (let rule of keyframesRule.cssRules) {
+              entries.push({
+                rule: this._styleRef(rule),
+                keyframes: this._styleRef(keyframesRule)
+              });
+            }
+          }
+        }
+      }
+    }
+
+    let rules = new Set();
+    let sheets = new Set();
+    entries.forEach(entry => rules.add(entry.rule));
+    this.expandSets(rules, sheets);
+
+    return {
+      entries: entries,
+      rules: [...rules],
+      sheets: [...sheets]
+    };
+  },
+
+  /**
+   * Expand Sets of rules and sheets to include all parent rules and sheets.
+   */
+  expandSets: function (ruleSet, sheetSet) {
+    // Sets include new items in their iteration
+    for (let rule of ruleSet) {
+      if (rule.rawRule.parentRule) {
+        let parent = this._styleRef(rule.rawRule.parentRule);
+        if (!ruleSet.has(parent)) {
+          ruleSet.add(parent);
+        }
+      }
+      if (rule.rawRule.parentStyleSheet) {
+        let parent = this._sheetRef(rule.rawRule.parentStyleSheet);
+        if (!sheetSet.has(parent)) {
+          sheetSet.add(parent);
+        }
+      }
+    }
+
+    for (let sheet of sheetSet) {
+      if (sheet.rawSheet.parentStyleSheet) {
+        let parent = this._sheetRef(sheet.rawSheet.parentStyleSheet);
+        if (!sheetSet.has(parent)) {
+          sheetSet.add(parent);
+        }
+      }
+    }
+  },
+
+  /**
+   * Get layout-related information about a node.
+   * This method returns an object with properties giving information about
+   * the node's margin, border, padding and content region sizes, as well
+   * as information about the type of box, its position, z-index, etc...
+   * @param {NodeActor} node
+   * @param {Object} options The only available option is autoMargins.
+   * If set to true, the element's margins will receive an extra check to see
+   * whether they are set to "auto" (knowing that the computed-style in this
+   * case would return "0px").
+   * The returned object will contain an extra property (autoMargins) listing
+   * all margins that are set to auto, e.g. {top: "auto", left: "auto"}.
+   * @return {Object}
+   */
+  getLayout: function (node, options) {
+    this.cssLogic.highlight(node.rawNode);
+
+    let layout = {};
+
+    // First, we update the first part of the box model view, with
+    // the size of the element.
+
+    let clientRect = node.rawNode.getBoundingClientRect();
+    layout.width = parseFloat(clientRect.width.toPrecision(6));
+    layout.height = parseFloat(clientRect.height.toPrecision(6));
+
+    // We compute and update the values of margins & co.
+    let style = CssLogic.getComputedStyle(node.rawNode);
+    for (let prop of [
+      "position",
+      "margin-top",
+      "margin-right",
+      "margin-bottom",
+      "margin-left",
+      "padding-top",
+      "padding-right",
+      "padding-bottom",
+      "padding-left",
+      "border-top-width",
+      "border-right-width",
+      "border-bottom-width",
+      "border-left-width",
+      "z-index",
+      "box-sizing",
+      "display"
+    ]) {
+      layout[prop] = style.getPropertyValue(prop);
+    }
+
+    if (options.autoMargins) {
+      layout.autoMargins = this.processMargins(this.cssLogic);
+    }
+
+    for (let i in this.map) {
+      let property = this.map[i].property;
+      this.map[i].value = parseFloat(style.getPropertyValue(property));
+    }
+
+    return layout;
+  },
+
+  /**
+   * Find 'auto' margin properties.
+   */
+  processMargins: function (cssLogic) {
+    let margins = {};
+
+    for (let prop of ["top", "bottom", "left", "right"]) {
+      let info = cssLogic.getPropertyInfo("margin-" + prop);
+      let selectors = info.matchedSelectors;
+      if (selectors && selectors.length > 0 && selectors[0].value == "auto") {
+        margins[prop] = "auto";
+      }
+    }
+
+    return margins;
+  },
+
+  /**
+   * On page navigation, tidy up remaining objects.
+   */
+  onFrameUnload: function () {
+    this.styleElements = new WeakMap();
+  },
+
+  /**
+   * When a stylesheet is added, handle the related StyleSheetActor to listen for changes.
+   * @param  {StyleSheetActor} actor
+   *         The actor for the added stylesheet.
+   */
+  onStyleSheetAdded: function (actor) {
+    if (!this._watchedSheets.has(actor)) {
+      this._watchedSheets.add(actor);
+      actor.on("style-applied", this._styleApplied);
+    }
+  },
+
+  /**
+   * Helper function to addNewRule to get or create a style tag in the provided
+   * document.
+   *
+   * @param {Document} document
+   *        The document in which the style element should be appended.
+   * @returns DOMElement of the style tag
+   */
+  getStyleElement: function (document) {
+    if (!this.styleElements.has(document)) {
+      let style = document.createElementNS(XHTML_NS, "style");
+      style.setAttribute("type", "text/css");
+      document.documentElement.appendChild(style);
+      this.styleElements.set(document, style);
+    }
+
+    return this.styleElements.get(document);
+  },
+
+  /**
+   * Helper function for adding a new rule and getting its applied style
+   * properties
+   * @param NodeActor node
+   * @param CSSStyleRule rule
+   * @returns Object containing its applied style properties
+   */
+  getNewAppliedProps: function (node, rule) {
+    let ruleActor = this._styleRef(rule);
+    return this.getAppliedProps(node, [{ rule: ruleActor }],
+      { matchedSelectors: true });
+  },
+
+  /**
+   * Adds a new rule, and returns the new StyleRuleActor.
+   * @param {NodeActor} node
+   * @param {String} pseudoClasses The list of pseudo classes to append to the
+   *        new selector.
+   * @param {Boolean} editAuthored
+   *        True if the selector should be updated by editing the
+   *        authored text; false if the selector should be updated via
+   *        CSSOM.
+   * @returns {StyleRuleActor} the new rule
+   */
+  addNewRule: Task.async(function* (node, pseudoClasses, editAuthored = false) {
+    let style = this.getStyleElement(node.rawNode.ownerDocument);
+    let sheet = style.sheet;
+    let cssRules = sheet.cssRules;
+    let rawNode = node.rawNode;
+    let classes = [...rawNode.classList];
+
+    let selector;
+    if (rawNode.id) {
+      selector = "#" + CSS.escape(rawNode.id);
+    } else if (classes.length > 0) {
+      selector = "." + classes.map(c => CSS.escape(c)).join(".");
+    } else {
+      selector = rawNode.localName;
+    }
+
+    if (pseudoClasses && pseudoClasses.length > 0) {
+      selector += pseudoClasses.join("");
+    }
+
+    let index = sheet.insertRule(selector + " {}", cssRules.length);
+
+    // If inserting the rule succeeded, go ahead and edit the source
+    // text if requested.
+    if (editAuthored) {
+      let sheetActor = this._sheetRef(sheet);
+      let {str: authoredText} = yield sheetActor.getText();
+      authoredText += "\n" + selector + " {\n" + "}";
+      yield sheetActor.update(authoredText, false);
+    }
+
+    return this.getNewAppliedProps(node, sheet.cssRules.item(index));
+  })
+});
+exports.PageStyleActor = PageStyleActor;
+
+/**
+ * An actor that represents a CSS style object on the protocol.
+ *
+ * We slightly flatten the CSSOM for this actor, it represents
+ * both the CSSRule and CSSStyle objects in one actor.  For nodes
+ * (which have a CSSStyle but no CSSRule) we create a StyleRuleActor
+ * with a special rule type (100).
+ */
+var StyleRuleActor = protocol.ActorClassWithSpec(styleRuleSpec, {
+  initialize: function (pageStyle, item) {
+    protocol.Actor.prototype.initialize.call(this, null);
+    this.pageStyle = pageStyle;
+    this.rawStyle = item.style;
+    this._parentSheet = null;
+    this._onStyleApplied = this._onStyleApplied.bind(this);
+
+    if (item instanceof (Ci.nsIDOMCSSRule)) {
+      this.type = item.type;
+      this.rawRule = item;
+      if ((this.type === Ci.nsIDOMCSSRule.STYLE_RULE ||
+           this.type === Ci.nsIDOMCSSRule.KEYFRAME_RULE) &&
+          this.rawRule.parentStyleSheet) {
+        this.line = DOMUtils.getRelativeRuleLine(this.rawRule);
+        this.column = DOMUtils.getRuleColumn(this.rawRule);
+        this._parentSheet = this.rawRule.parentStyleSheet;
+        this._computeRuleIndex();
+        this.sheetActor = this.pageStyle._sheetRef(this._parentSheet);
+        this.sheetActor.on("style-applied", this._onStyleApplied);
+      }
+    } else {
+      // Fake a rule
+      this.type = ELEMENT_STYLE;
+      this.rawNode = item;
+      this.rawRule = {
+        style: item.style,
+        toString: function () {
+          return "[element rule " + this.style + "]";
+        }
+      };
+    }
+  },
+
+  get conn() {
+    return this.pageStyle.conn;
+  },
+
+  destroy: function () {
+    if (!this.rawStyle) {
+      return;
+    }
+    protocol.Actor.prototype.destroy.call(this);
+    this.rawStyle = null;
+    this.pageStyle = null;
+    this.rawNode = null;
+    this.rawRule = null;
+    if (this.sheetActor) {
+      this.sheetActor.off("style-applied", this._onStyleApplied);
+    }
+  },
+
+  // Objects returned by this actor are owned by the PageStyleActor
+  // to which this rule belongs.
+  get marshallPool() {
+    return this.pageStyle;
+  },
+
+  // True if this rule supports as-authored styles, meaning that the
+  // rule text can be rewritten using setRuleText.
+  get canSetRuleText() {
+    return this.type === ELEMENT_STYLE ||
+           (this._parentSheet &&
+            // If a rule does not have source, then it has been modified via
+            // CSSOM; and we should fall back to non-authored editing.
+            // https://bugzilla.mozilla.org/show_bug.cgi?id=1224121
+            this.sheetActor.allRulesHaveSource() &&
+            // Special case about:PreferenceStyleSheet, as it is generated on
+            // the fly and the URI is not registered with the about:handler
+            // https://bugzilla.mozilla.org/show_bug.cgi?id=935803#c37
+            this._parentSheet.href !== "about:PreferenceStyleSheet");
+  },
+
+  getDocument: function (sheet) {
+    let document;
+
+    if (sheet.ownerNode instanceof Ci.nsIDOMHTMLDocument) {
+      document = sheet.ownerNode;
+    } else {
+      document = sheet.ownerNode.ownerDocument;
+    }
+
+    return document;
+  },
+
+  toString: function () {
+    return "[StyleRuleActor for " + this.rawRule + "]";
+  },
+
+  form: function (detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    let form = {
+      actor: this.actorID,
+      type: this.type,
+      line: this.line || undefined,
+      column: this.column,
+      traits: {
+        // Whether the style rule actor implements the modifySelector2 method
+        // that allows for unmatched rule to be added
+        modifySelectorUnmatched: true,
+        // Whether the style rule actor implements the setRuleText
+        // method.
+        canSetRuleText: this.canSetRuleText,
+      }
+    };
+
+    if (this.rawRule.parentRule) {
+      form.parentRule =
+        this.pageStyle._styleRef(this.rawRule.parentRule).actorID;
+
+      // CSS rules that we call media rules are STYLE_RULES that are children
+      // of MEDIA_RULEs. We need to check the parentRule to check if a rule is
+      // a media rule so we do this here instead of in the switch statement
+      // below.
+      if (this.rawRule.parentRule.type === Ci.nsIDOMCSSRule.MEDIA_RULE) {
+        form.media = [];
+        for (let i = 0, n = this.rawRule.parentRule.media.length; i < n; i++) {
+          form.media.push(this.rawRule.parentRule.media.item(i));
+        }
+      }
+    }
+    if (this._parentSheet) {
+      form.parentStyleSheet =
+        this.pageStyle._sheetRef(this._parentSheet).actorID;
+    }
+
+    // One tricky thing here is that other methods in this actor must
+    // ensure that authoredText has been set before |form| is called.
+    // This has to be treated specially, for now, because we cannot
+    // synchronously compute the authored text, but |form| also cannot
+    // return a promise.  See bug 1205868.
+    form.authoredText = this.authoredText;
+
+    switch (this.type) {
+      case Ci.nsIDOMCSSRule.STYLE_RULE:
+        form.selectors = CssLogic.getSelectors(this.rawRule);
+        form.cssText = this.rawStyle.cssText || "";
+        break;
+      case ELEMENT_STYLE:
+        // Elements don't have a parent stylesheet, and therefore
+        // don't have an associated URI.  Provide a URI for
+        // those.
+        let doc = this.rawNode.ownerDocument;
+        form.href = doc.location ? doc.location.href : "";
+        form.cssText = this.rawStyle.cssText || "";
+        form.authoredText = this.rawNode.getAttribute("style");
+        break;
+      case Ci.nsIDOMCSSRule.CHARSET_RULE:
+        form.encoding = this.rawRule.encoding;
+        break;
+      case Ci.nsIDOMCSSRule.IMPORT_RULE:
+        form.href = this.rawRule.href;
+        break;
+      case Ci.nsIDOMCSSRule.KEYFRAMES_RULE:
+        form.cssText = this.rawRule.cssText;
+        form.name = this.rawRule.name;
+        break;
+      case Ci.nsIDOMCSSRule.KEYFRAME_RULE:
+        form.cssText = this.rawStyle.cssText || "";
+        form.keyText = this.rawRule.keyText || "";
+        break;
+    }
+
+    // Parse the text into a list of declarations so the client doesn't have to
+    // and so that we can safely determine if a declaration is valid rather than
+    // have the client guess it.
+    if (form.authoredText || form.cssText) {
+      let declarations = parseDeclarations(isCssPropertyKnown,
+                                           form.authoredText || form.cssText,
+                                           true);
+      form.declarations = declarations.map(decl => {
+        decl.isValid = DOMUtils.cssPropertyIsValid(decl.name, decl.value);
+        return decl;
+      });
+    }
+
+    return form;
+  },
+
+  /**
+   * Send an event notifying that the location of the rule has
+   * changed.
+   *
+   * @param {Number} line the new line number
+   * @param {Number} column the new column number
+   */
+  _notifyLocationChanged: function (line, column) {
+    events.emit(this, "location-changed", line, column);
+  },
+
+  /**
+   * Compute the index of this actor's raw rule in its parent style
+   * sheet.  The index is a vector where each element is the index of
+   * a given CSS rule in its parent.  A vector is used to support
+   * nested rules.
+   */
+  _computeRuleIndex: function () {
+    let rule = this.rawRule;
+    let result = [];
+
+    while (rule) {
+      let cssRules;
+      if (rule.parentRule) {
+        cssRules = rule.parentRule.cssRules;
+      } else {
+        cssRules = rule.parentStyleSheet.cssRules;
+      }
+
+      let found = false;
+      for (let i = 0; i < cssRules.length; i++) {
+        if (rule === cssRules.item(i)) {
+          found = true;
+          result.unshift(i);
+          break;
+        }
+      }
+
+      if (!found) {
+        this._ruleIndex = null;
+        return;
+      }
+
+      rule = rule.parentRule;
+    }
+
+    this._ruleIndex = result;
+  },
+
+  /**
+   * Get the rule corresponding to |this._ruleIndex| from the given
+   * style sheet.
+   *
+   * @param  {DOMStyleSheet} sheet
+   *         The style sheet.
+   * @return {CSSStyleRule} the rule corresponding to
+   * |this._ruleIndex|
+   */
+  _getRuleFromIndex: function (parentSheet) {
+    let currentRule = null;
+    for (let i of this._ruleIndex) {
+      if (currentRule === null) {
+        currentRule = parentSheet.cssRules[i];
+      } else {
+        currentRule = currentRule.cssRules.item(i);
+      }
+    }
+    return currentRule;
+  },
+
+  /**
+   * This is attached to the parent style sheet actor's
+   * "style-applied" event.
+   */
+  _onStyleApplied: function (kind) {
+    if (kind === UPDATE_GENERAL) {
+      // A general change means that the rule actors are invalidated,
+      // so stop listening to events now.
+      if (this.sheetActor) {
+        this.sheetActor.off("style-applied", this._onStyleApplied);
+      }
+    } else if (this._ruleIndex) {
+      // The sheet was updated by this actor, in a way that preserves
+      // the rules.  Now, recompute our new rule from the style sheet,
+      // so that we aren't left with a reference to a dangling rule.
+      let oldRule = this.rawRule;
+      this.rawRule = this._getRuleFromIndex(this._parentSheet);
+      // Also tell the page style so that future calls to _styleRef
+      // return the same StyleRuleActor.
+      this.pageStyle.updateStyleRef(oldRule, this.rawRule, this);
+      let line = DOMUtils.getRelativeRuleLine(this.rawRule);
+      let column = DOMUtils.getRuleColumn(this.rawRule);
+      if (line !== this.line || column !== this.column) {
+        this._notifyLocationChanged(line, column);
+      }
+      this.line = line;
+      this.column = column;
+    }
+  },
+
+  /**
+   * Return a promise that resolves to the authored form of a rule's
+   * text, if available.  If the authored form is not available, the
+   * returned promise simply resolves to the empty string.  If the
+   * authored form is available, this also sets |this.authoredText|.
+   * The authored text will include invalid and otherwise ignored
+   * properties.
+   */
+  getAuthoredCssText: function () {
+    if (!this.canSetRuleText ||
+        (this.type !== Ci.nsIDOMCSSRule.STYLE_RULE &&
+         this.type !== Ci.nsIDOMCSSRule.KEYFRAME_RULE)) {
+      return promise.resolve("");
+    }
+
+    if (typeof this.authoredText === "string") {
+      return promise.resolve(this.authoredText);
+    }
+
+    let parentStyleSheet =
+        this.pageStyle._sheetRef(this._parentSheet);
+    return parentStyleSheet.getText().then((longStr) => {
+      let cssText = longStr.str;
+      let {text} = getRuleText(cssText, this.line, this.column);
+
+      // Cache the result on the rule actor to avoid parsing again next time
+      this.authoredText = text;
+      return this.authoredText;
+    });
+  },
+
+  /**
+   * Set the contents of the rule.  This rewrites the rule in the
+   * stylesheet and causes it to be re-evaluated.
+   *
+   * @param {String} newText the new text of the rule
+   * @returns the rule with updated properties
+   */
+  setRuleText: Task.async(function* (newText) {
+    if (!this.canSetRuleText) {
+      throw new Error("invalid call to setRuleText");
+    }
+
+    if (this.type === ELEMENT_STYLE) {
+      // For element style rules, set the node's style attribute.
+      this.rawNode.setAttribute("style", newText);
+    } else {
+      // For stylesheet rules, set the text in the stylesheet.
+      let parentStyleSheet = this.pageStyle._sheetRef(this._parentSheet);
+      let {str: cssText} = yield parentStyleSheet.getText();
+
+      let {offset, text} = getRuleText(cssText, this.line, this.column);
+      cssText = cssText.substring(0, offset) + newText +
+        cssText.substring(offset + text.length);
+
+      yield parentStyleSheet.update(cssText, false, UPDATE_PRESERVING_RULES);
+    }
+
+    this.authoredText = newText;
+
+    return this;
+  }),
+
+  /**
+   * Modify a rule's properties. Passed an array of modifications:
+   * {
+   *   type: "set",
+   *   name: <string>,
+   *   value: <string>,
+   *   priority: <optional string>
+   * }
+   *  or
+   * {
+   *   type: "remove",
+   *   name: <string>,
+   * }
+   *
+   * @returns the rule with updated properties
+   */
+  modifyProperties: function (modifications) {
+    // Use a fresh element for each call to this function to prevent side
+    // effects that pop up based on property values that were already set on the
+    // element.
+
+    let document;
+    if (this.rawNode) {
+      document = this.rawNode.ownerDocument;
+    } else {
+      let parentStyleSheet = this._parentSheet;
+      while (parentStyleSheet.ownerRule &&
+          parentStyleSheet.ownerRule instanceof Ci.nsIDOMCSSImportRule) {
+        parentStyleSheet = parentStyleSheet.ownerRule.parentStyleSheet;
+      }
+
+      document = this.getDocument(parentStyleSheet);
+    }
+
+    let tempElement = document.createElementNS(XHTML_NS, "div");
+
+    for (let mod of modifications) {
+      if (mod.type === "set") {
+        tempElement.style.setProperty(mod.name, mod.value, mod.priority || "");
+        this.rawStyle.setProperty(mod.name,
+          tempElement.style.getPropertyValue(mod.name), mod.priority || "");
+      } else if (mod.type === "remove") {
+        this.rawStyle.removeProperty(mod.name);
+      }
+    }
+
+    return this;
+  },
+
+  /**
+   * Helper function for modifySelector and modifySelector2, inserts the new
+   * rule with the new selector into the parent style sheet and removes the
+   * current rule. Returns the newly inserted css rule or null if the rule is
+   * unsuccessfully inserted to the parent style sheet.
+   *
+   * @param {String} value
+   *        The new selector value
+   * @param {Boolean} editAuthored
+   *        True if the selector should be updated by editing the
+   *        authored text; false if the selector should be updated via
+   *        CSSOM.
+   *
+   * @returns {CSSRule}
+   *        The new CSS rule added
+   */
+  _addNewSelector: Task.async(function* (value, editAuthored) {
+    let rule = this.rawRule;
+    let parentStyleSheet = this._parentSheet;
+
+    // We know the selector modification is ok, so if the client asked
+    // for the authored text to be edited, do it now.
+    if (editAuthored) {
+      let document = this.getDocument(this._parentSheet);
+      try {
+        document.querySelector(value);
+      } catch (e) {
+        return null;
+      }
+
+      let sheetActor = this.pageStyle._sheetRef(parentStyleSheet);
+      let {str: authoredText} = yield sheetActor.getText();
+      let [startOffset, endOffset] = getSelectorOffsets(authoredText, this.line,
+                                                        this.column);
+      authoredText = authoredText.substring(0, startOffset) + value +
+        authoredText.substring(endOffset);
+      yield sheetActor.update(authoredText, false, UPDATE_PRESERVING_RULES);
+    } else {
+      let cssRules = parentStyleSheet.cssRules;
+      let cssText = rule.cssText;
+      let selectorText = rule.selectorText;
+
+      for (let i = 0; i < cssRules.length; i++) {
+        if (rule === cssRules.item(i)) {
+          try {
+            // Inserts the new style rule into the current style sheet and
+            // delete the current rule
+            let ruleText = cssText.slice(selectorText.length).trim();
+            parentStyleSheet.insertRule(value + " " + ruleText, i);
+            parentStyleSheet.deleteRule(i + 1);
+            break;
+          } catch (e) {
+            // The selector could be invalid, or the rule could fail to insert.
+            return null;
+          }
+        }
+      }
+    }
+
+    return this._getRuleFromIndex(parentStyleSheet);
+  }),
+
+  /**
+   * Modify the current rule's selector by inserting a new rule with the new
+   * selector value and removing the current rule.
+   *
+   * Note this method was kept for backward compatibility, but unmatched rules
+   * support was added in FF41.
+   *
+   * @param string value
+   *        The new selector value
+   * @returns boolean
+   *        Returns a boolean if the selector in the stylesheet was modified,
+   *        and false otherwise
+   */
+  modifySelector: Task.async(function* (value) {
+    if (this.type === ELEMENT_STYLE) {
+      return false;
+    }
+
+    let document = this.getDocument(this._parentSheet);
+    // Extract the selector, and pseudo elements and classes
+    let [selector] = value.split(/(:{1,2}.+$)/);
+    let selectorElement;
+
+    try {
+      selectorElement = document.querySelector(selector);
+    } catch (e) {
+      return false;
+    }
+
+    // Check if the selector is valid and not the same as the original
+    // selector
+    if (selectorElement && this.rawRule.selectorText !== value) {
+      yield this._addNewSelector(value, false);
+      return true;
+    }
+    return false;
+  }),
+
+  /**
+   * Modify the current rule's selector by inserting a new rule with the new
+   * selector value and removing the current rule.
+   *
+   * In contrast with the modifySelector method which was used before FF41,
+   * this method also returns information about the new rule and applied style
+   * so that consumers can immediately display the new rule, whether or not the
+   * selector matches the current element without having to refresh the whole
+   * list.
+   *
+   * @param {DOMNode} node
+   *        The current selected element
+   * @param {String} value
+   *        The new selector value
+   * @param {Boolean} editAuthored
+   *        True if the selector should be updated by editing the
+   *        authored text; false if the selector should be updated via
+   *        CSSOM.
+   * @returns {Object}
+   *        Returns an object that contains the applied style properties of the
+   *        new rule and a boolean indicating whether or not the new selector
+   *        matches the current selected element
+   */
+  modifySelector2: function (node, value, editAuthored = false) {
+    if (this.type === ELEMENT_STYLE ||
+        this.rawRule.selectorText === value) {
+      return { ruleProps: null, isMatching: true };
+    }
+
+    let selectorPromise = this._addNewSelector(value, editAuthored);
+
+    if (editAuthored) {
+      selectorPromise = selectorPromise.then((newCssRule) => {
+        if (newCssRule) {
+          let style = this.pageStyle._styleRef(newCssRule);
+          // See the comment in |form| to understand this.
+          return style.getAuthoredCssText().then(() => newCssRule);
+        }
+        return newCssRule;
+      });
+    }
+
+    return selectorPromise.then((newCssRule) => {
+      let ruleProps = null;
+      let isMatching = false;
+
+      if (newCssRule) {
+        let ruleEntry = this.pageStyle.findEntryMatchingRule(node, newCssRule);
+        if (ruleEntry.length === 1) {
+          ruleProps =
+            this.pageStyle.getAppliedProps(node, ruleEntry,
+                                           { matchedSelectors: true });
+        } else {
+          ruleProps = this.pageStyle.getNewAppliedProps(node, newCssRule);
+        }
+
+        isMatching = ruleProps.entries.some((ruleProp) =>
+          ruleProp.matchedSelectors.length > 0);
+      }
+
+      return { ruleProps, isMatching };
+    });
+  }
+});
+
+/**
+ * Helper function for getting an image preview of the given font.
+ *
+ * @param font {string}
+ *        Name of font to preview
+ * @param doc {Document}
+ *        Document to use to render font
+ * @param options {object}
+ *        Object with options 'previewText' and 'previewFontSize'
+ *
+ * @return dataUrl
+ *         The data URI of the font preview image
+ */
+function getFontPreviewData(font, doc, options) {
+  options = options || {};
+  let previewText = options.previewText || FONT_PREVIEW_TEXT;
+  let previewFontSize = options.previewFontSize || FONT_PREVIEW_FONT_SIZE;
+  let fillStyle = options.fillStyle || FONT_PREVIEW_FILLSTYLE;
+  let fontStyle = options.fontStyle || "";
+
+  let canvas = doc.createElementNS(XHTML_NS, "canvas");
+  let ctx = canvas.getContext("2d");
+  let fontValue = fontStyle + " " + previewFontSize + "px " + font + ", serif";
+
+  // Get the correct preview text measurements and set the canvas dimensions
+  ctx.font = fontValue;
+  ctx.fillStyle = fillStyle;
+  let textWidth = ctx.measureText(previewText).width;
+
+  canvas.width = textWidth * 2 + FONT_PREVIEW_OFFSET * 2;
+  canvas.height = previewFontSize * 3;
+
+  // we have to reset these after changing the canvas size
+  ctx.font = fontValue;
+  ctx.fillStyle = fillStyle;
+
+  // Oversample the canvas for better text quality
+  ctx.textBaseline = "top";
+  ctx.scale(2, 2);
+  ctx.fillText(previewText,
+               FONT_PREVIEW_OFFSET,
+               Math.round(previewFontSize / 3));
+
+  let dataURL = canvas.toDataURL("image/png");
+
+  return {
+    dataURL: dataURL,
+    size: textWidth + FONT_PREVIEW_OFFSET * 2
+  };
+}
+
+exports.getFontPreviewData = getFontPreviewData;
+
+/**
+ * Get the text content of a rule given some CSS text, a line and a column
+ * Consider the following example:
+ * body {
+ *  color: red;
+ * }
+ * p {
+ *  line-height: 2em;
+ *  color: blue;
+ * }
+ * Calling the function with the whole text above and line=4 and column=1 would
+ * return "line-height: 2em; color: blue;"
+ * @param {String} initialText
+ * @param {Number} line (1-indexed)
+ * @param {Number} column (1-indexed)
+ * @return {object} An object of the form {offset: number, text: string}
+ *                  The offset is the index into the input string where
+ *                  the rule text started.  The text is the content of
+ *                  the rule.
+ */
+function getRuleText(initialText, line, column) {
+  if (typeof line === "undefined" || typeof column === "undefined") {
+    throw new Error("Location information is missing");
+  }
+
+  let {offset: textOffset, text} =
+      getTextAtLineColumn(initialText, line, column);
+  let lexer = DOMUtils.getCSSLexer(text);
+
+  // Search forward for the opening brace.
+  while (true) {
+    let token = lexer.nextToken();
+    if (!token) {
+      throw new Error("couldn't find start of the rule");
+    }
+    if (token.tokenType === "symbol" && token.text === "{") {
+      break;
+    }
+  }
+
+  // Now collect text until we see the matching close brace.
+  let braceDepth = 1;
+  let startOffset, endOffset;
+  while (true) {
+    let token = lexer.nextToken();
+    if (!token) {
+      break;
+    }
+    if (startOffset === undefined) {
+      startOffset = token.startOffset;
+    }
+    if (token.tokenType === "symbol") {
+      if (token.text === "{") {
+        ++braceDepth;
+      } else if (token.text === "}") {
+        --braceDepth;
+        if (braceDepth == 0) {
+          break;
+        }
+      }
+    }
+    endOffset = token.endOffset;
+  }
+
+  // If the rule was of the form "selector {" with no closing brace
+  // and no properties, just return an empty string.
+  if (startOffset === undefined) {
+    return {offset: 0, text: ""};
+  }
+  // If the input didn't have any tokens between the braces (e.g.,
+  // "div {}"), then the endOffset won't have been set yet; so account
+  // for that here.
+  if (endOffset === undefined) {
+    endOffset = startOffset;
+  }
+
+  // Note that this approach will preserve comments, despite the fact
+  // that cssTokenizer skips them.
+  return {offset: textOffset + startOffset,
+          text: text.substring(startOffset, endOffset)};
+}
+
+exports.getRuleText = getRuleText;
+
+/**
+ * Compute the start and end offsets of a rule's selector text, given
+ * the CSS text and the line and column at which the rule begins.
+ * @param {String} initialText
+ * @param {Number} line (1-indexed)
+ * @param {Number} column (1-indexed)
+ * @return {array} An array with two elements: [startOffset, endOffset].
+ *                 The elements mark the bounds in |initialText| of
+ *                 the CSS rule's selector.
+ */
+function getSelectorOffsets(initialText, line, column) {
+  if (typeof line === "undefined" || typeof column === "undefined") {
+    throw new Error("Location information is missing");
+  }
+
+  let {offset: textOffset, text} =
+      getTextAtLineColumn(initialText, line, column);
+  let lexer = DOMUtils.getCSSLexer(text);
+
+  // Search forward for the opening brace.
+  let endOffset;
+  while (true) {
+    let token = lexer.nextToken();
+    if (!token) {
+      break;
+    }
+    if (token.tokenType === "symbol" && token.text === "{") {
+      if (endOffset === undefined) {
+        break;
+      }
+      return [textOffset, textOffset + endOffset];
+    }
+    // Preserve comments and whitespace just before the "{".
+    if (token.tokenType !== "comment" && token.tokenType !== "whitespace") {
+      endOffset = token.endOffset;
+    }
+  }
+
+  throw new Error("could not find bounds of rule");
+}
+
+/**
+ * Return the offset and substring of |text| that starts at the given
+ * line and column.
+ * @param {String} text
+ * @param {Number} line (1-indexed)
+ * @param {Number} column (1-indexed)
+ * @return {object} An object of the form {offset: number, text: string},
+ *                  where the offset is the offset into the input string
+ *                  where the text starts, and where text is the text.
+ */
+function getTextAtLineColumn(text, line, column) {
+  let offset;
+  if (line > 1) {
+    let rx = new RegExp("(?:.*(?:\\r\\n|\\n|\\r|\\f)){" + (line - 1) + "}");
+    offset = rx.exec(text)[0].length;
+  } else {
+    offset = 0;
+  }
+  offset += column - 1;
+  return {offset: offset, text: text.substr(offset) };
+}
+
+exports.getTextAtLineColumn = getTextAtLineColumn;
diff --git a/devtools/server/actors/stylesheets.js b/devtools/server/actors/stylesheets.js
new file mode 100644
index 000000000..f20634e6c
--- /dev/null
+++ b/devtools/server/actors/stylesheets.js
@@ -0,0 +1,982 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {Cc, Ci} = require("chrome");
+const Services = require("Services");
+const {XPCOMUtils} = require("resource://gre/modules/XPCOMUtils.jsm");
+const promise = require("promise");
+const {Task} = require("devtools/shared/task");
+const events = require("sdk/event/core");
+const protocol = require("devtools/shared/protocol");
+const {LongStringActor} = require("devtools/server/actors/string");
+const {fetch} = require("devtools/shared/DevToolsUtils");
+const {listenOnce} = require("devtools/shared/async-utils");
+const {originalSourceSpec, mediaRuleSpec, styleSheetSpec,
+       styleSheetsSpec} = require("devtools/shared/specs/stylesheets");
+const {SourceMapConsumer} = require("source-map");
+const { installHelperSheet,
+  addPseudoClassLock, removePseudoClassLock } = require("devtools/server/actors/highlighters/utils/markup");
+
+loader.lazyGetter(this, "CssLogic", () => require("devtools/shared/inspector/css-logic"));
+
+XPCOMUtils.defineLazyGetter(this, "DOMUtils", function () {
+  return Cc["@mozilla.org/inspector/dom-utils;1"].getService(Ci.inIDOMUtils);
+});
+
+var TRANSITION_PSEUDO_CLASS = ":-moz-styleeditor-transitioning";
+var TRANSITION_DURATION_MS = 500;
+var TRANSITION_BUFFER_MS = 1000;
+var TRANSITION_RULE_SELECTOR =
+`:root${TRANSITION_PSEUDO_CLASS}, :root${TRANSITION_PSEUDO_CLASS} *`;
+var TRANSITION_RULE = `${TRANSITION_RULE_SELECTOR} {
+  transition-duration: ${TRANSITION_DURATION_MS}ms !important;
+  transition-delay: 0ms !important;
+  transition-timing-function: ease-out !important;
+  transition-property: all !important;
+}`;
+
+var LOAD_ERROR = "error-load";
+
+// The possible kinds of style-applied events.
+// UPDATE_PRESERVING_RULES means that the update is guaranteed to
+// preserve the number and order of rules on the style sheet.
+// UPDATE_GENERAL covers any other kind of change to the style sheet.
+const UPDATE_PRESERVING_RULES = 0;
+exports.UPDATE_PRESERVING_RULES = UPDATE_PRESERVING_RULES;
+const UPDATE_GENERAL = 1;
+exports.UPDATE_GENERAL = UPDATE_GENERAL;
+
+// If the user edits a style sheet, we stash a copy of the edited text
+// here, keyed by the style sheet.  This way, if the tools are closed
+// and then reopened, the edited text will be available.  A weak map
+// is used so that navigation by the user will eventually cause the
+// edited text to be collected.
+let modifiedStyleSheets = new WeakMap();
+
+/**
+ * Actor representing an original source of a style sheet that was specified
+ * in a source map.
+ */
+var OriginalSourceActor = protocol.ActorClassWithSpec(originalSourceSpec, {
+  initialize: function (aUrl, aSourceMap, aParentActor) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this.url = aUrl;
+    this.sourceMap = aSourceMap;
+    this.parentActor = aParentActor;
+    this.conn = this.parentActor.conn;
+
+    this.text = null;
+  },
+
+  form: function () {
+    return {
+      actor: this.actorID, // actorID is set when it's added to a pool
+      url: this.url,
+      relatedStyleSheet: this.parentActor.form()
+    };
+  },
+
+  _getText: function () {
+    if (this.text) {
+      return promise.resolve(this.text);
+    }
+    let content = this.sourceMap.sourceContentFor(this.url);
+    if (content) {
+      this.text = content;
+      return promise.resolve(content);
+    }
+    let options = {
+      policy: Ci.nsIContentPolicy.TYPE_INTERNAL_STYLESHEET,
+      window: this.window
+    };
+    return fetch(this.url, options).then(({content}) => {
+      this.text = content;
+      return content;
+    });
+  },
+
+  /**
+   * Protocol method to get the text of this source.
+   */
+  getText: function () {
+    return this._getText().then((text) => {
+      return new LongStringActor(this.conn, text || "");
+    });
+  }
+});
+
+/**
+ * A MediaRuleActor lives on the server and provides access to properties
+ * of a DOM @media rule and emits events when it changes.
+ */
+var MediaRuleActor = protocol.ActorClassWithSpec(mediaRuleSpec, {
+  get window() {
+    return this.parentActor.window;
+  },
+
+  get document() {
+    return this.window.document;
+  },
+
+  get matches() {
+    return this.mql ? this.mql.matches : null;
+  },
+
+  initialize: function (aMediaRule, aParentActor) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this.rawRule = aMediaRule;
+    this.parentActor = aParentActor;
+    this.conn = this.parentActor.conn;
+
+    this._matchesChange = this._matchesChange.bind(this);
+
+    this.line = DOMUtils.getRuleLine(aMediaRule);
+    this.column = DOMUtils.getRuleColumn(aMediaRule);
+
+    try {
+      this.mql = this.window.matchMedia(aMediaRule.media.mediaText);
+    } catch (e) {
+    }
+
+    if (this.mql) {
+      this.mql.addListener(this._matchesChange);
+    }
+  },
+
+  destroy: function ()
+  {
+    if (this.mql) {
+      this.mql.removeListener(this._matchesChange);
+    }
+
+    protocol.Actor.prototype.destroy.call(this);
+  },
+
+  form: function (detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    let form = {
+      actor: this.actorID,  // actorID is set when this is added to a pool
+      mediaText: this.rawRule.media.mediaText,
+      conditionText: this.rawRule.conditionText,
+      matches: this.matches,
+      line: this.line,
+      column: this.column,
+      parentStyleSheet: this.parentActor.actorID
+    };
+
+    return form;
+  },
+
+  _matchesChange: function () {
+    events.emit(this, "matches-change", this.matches);
+  }
+});
+
+/**
+ * A StyleSheetActor represents a stylesheet on the server.
+ */
+var StyleSheetActor = protocol.ActorClassWithSpec(styleSheetSpec, {
+  /* List of original sources that generated this stylesheet */
+  _originalSources: null,
+
+  toString: function () {
+    return "[StyleSheetActor " + this.actorID + "]";
+  },
+
+  /**
+   * Window of target
+   */
+  get window() {
+    return this._window || this.parentActor.window;
+  },
+
+  /**
+   * Document of target.
+   */
+  get document() {
+    return this.window.document;
+  },
+
+  get ownerNode() {
+    return this.rawSheet.ownerNode;
+  },
+
+  /**
+   * URL of underlying stylesheet.
+   */
+  get href() {
+    return this.rawSheet.href;
+  },
+
+  /**
+   * Returns the stylesheet href or the document href if the sheet is inline.
+   */
+  get safeHref() {
+    let href = this.href;
+    if (!href) {
+      if (this.ownerNode instanceof Ci.nsIDOMHTMLDocument) {
+        href = this.ownerNode.location.href;
+      } else if (this.ownerNode.ownerDocument &&
+                 this.ownerNode.ownerDocument.location) {
+        href = this.ownerNode.ownerDocument.location.href;
+      }
+    }
+    return href;
+  },
+
+  /**
+   * Retrieve the index (order) of stylesheet in the document.
+   *
+   * @return number
+   */
+  get styleSheetIndex()
+  {
+    if (this._styleSheetIndex == -1) {
+      for (let i = 0; i < this.document.styleSheets.length; i++) {
+        if (this.document.styleSheets[i] == this.rawSheet) {
+          this._styleSheetIndex = i;
+          break;
+        }
+      }
+    }
+    return this._styleSheetIndex;
+  },
+
+  destroy: function () {
+    if (this._transitionTimeout) {
+      this.window.clearTimeout(this._transitionTimeout);
+      removePseudoClassLock(
+                   this.document.documentElement, TRANSITION_PSEUDO_CLASS);
+    }
+  },
+
+  /**
+   * Since StyleSheetActor doesn't have a protocol.js parent actor that take
+   * care of its lifetime, implementing disconnect is required to cleanup.
+   */
+  disconnect: function () {
+    this.destroy();
+  },
+
+  initialize: function (aStyleSheet, aParentActor, aWindow) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this.rawSheet = aStyleSheet;
+    this.parentActor = aParentActor;
+    this.conn = this.parentActor.conn;
+
+    this._window = aWindow;
+
+    // text and index are unknown until source load
+    this.text = null;
+    this._styleSheetIndex = -1;
+  },
+
+  /**
+   * Test whether all the rules in this sheet have associated source.
+   * @return {Boolean} true if all the rules have source; false if
+   *         some rule was created via CSSOM.
+   */
+  allRulesHaveSource: function () {
+    let rules;
+    try {
+      rules = this.rawSheet.cssRules;
+    } catch (e) {
+      // sheet isn't loaded yet
+      return true;
+    }
+
+    for (let i = 0; i < rules.length; i++) {
+      let rule = rules[i];
+      if (DOMUtils.getRelativeRuleLine(rule) === 0) {
+        return false;
+      }
+    }
+
+    return true;
+  },
+
+  /**
+   * Get the raw stylesheet's cssRules once the sheet has been loaded.
+   *
+   * @return {Promise}
+   *         Promise that resolves with a CSSRuleList
+   */
+  getCSSRules: function () {
+    let rules;
+    try {
+      rules = this.rawSheet.cssRules;
+    }
+    catch (e) {
+      // sheet isn't loaded yet
+    }
+
+    if (rules) {
+      return promise.resolve(rules);
+    }
+
+    if (!this.ownerNode) {
+      return promise.resolve([]);
+    }
+
+    if (this._cssRules) {
+      return this._cssRules;
+    }
+
+    let deferred = promise.defer();
+
+    let onSheetLoaded = (event) => {
+      this.ownerNode.removeEventListener("load", onSheetLoaded, false);
+
+      deferred.resolve(this.rawSheet.cssRules);
+    };
+
+    this.ownerNode.addEventListener("load", onSheetLoaded, false);
+
+    // cache so we don't add many listeners if this is called multiple times.
+    this._cssRules = deferred.promise;
+
+    return this._cssRules;
+  },
+
+  /**
+   * Get the current state of the actor
+   *
+   * @return {object}
+   *         With properties of the underlying stylesheet, plus 'text',
+   *        'styleSheetIndex' and 'parentActor' if it's @imported
+   */
+  form: function (detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    let docHref;
+    if (this.ownerNode) {
+      if (this.ownerNode instanceof Ci.nsIDOMHTMLDocument) {
+        docHref = this.ownerNode.location.href;
+      }
+      else if (this.ownerNode.ownerDocument && this.ownerNode.ownerDocument.location) {
+        docHref = this.ownerNode.ownerDocument.location.href;
+      }
+    }
+
+    let form = {
+      actor: this.actorID,  // actorID is set when this actor is added to a pool
+      href: this.href,
+      nodeHref: docHref,
+      disabled: this.rawSheet.disabled,
+      title: this.rawSheet.title,
+      system: !CssLogic.isContentStylesheet(this.rawSheet),
+      styleSheetIndex: this.styleSheetIndex
+    };
+
+    try {
+      form.ruleCount = this.rawSheet.cssRules.length;
+    }
+    catch (e) {
+      // stylesheet had an @import rule that wasn't loaded yet
+      this.getCSSRules().then(() => {
+        this._notifyPropertyChanged("ruleCount");
+      });
+    }
+    return form;
+  },
+
+  /**
+   * Toggle the disabled property of the style sheet
+   *
+   * @return {object}
+   *         'disabled' - the disabled state after toggling.
+   */
+  toggleDisabled: function () {
+    this.rawSheet.disabled = !this.rawSheet.disabled;
+    this._notifyPropertyChanged("disabled");
+
+    return this.rawSheet.disabled;
+  },
+
+  /**
+   * Send an event notifying that a property of the stylesheet
+   * has changed.
+   *
+   * @param  {string} property
+   *         Name of the changed property
+   */
+  _notifyPropertyChanged: function (property) {
+    events.emit(this, "property-change", property, this.form()[property]);
+  },
+
+  /**
+   * Protocol method to get the text of this stylesheet.
+   */
+  getText: function () {
+    return this._getText().then((text) => {
+      return new LongStringActor(this.conn, text || "");
+    });
+  },
+
+  /**
+   * Fetch the text for this stylesheet from the cache or network. Return
+   * cached text if it's already been fetched.
+   *
+   * @return {Promise}
+   *         Promise that resolves with a string text of the stylesheet.
+   */
+  _getText: function () {
+    if (typeof this.text === "string") {
+      return promise.resolve(this.text);
+    }
+
+    let cssText = modifiedStyleSheets.get(this.rawSheet);
+    if (cssText !== undefined) {
+      this.text = cssText;
+      return promise.resolve(cssText);
+    }
+
+    if (!this.href) {
+      // this is an inline <style> sheet
+      let content = this.ownerNode.textContent;
+      this.text = content;
+      return promise.resolve(content);
+    }
+
+    let options = {
+      loadFromCache: true,
+      policy: Ci.nsIContentPolicy.TYPE_INTERNAL_STYLESHEET,
+      charset: this._getCSSCharset()
+    };
+
+    // Bug 1282660 - We use the system principal to load the default internal
+    // stylesheets instead of the content principal since such stylesheets
+    // require system principal to load. At meanwhile, we strip the loadGroup
+    // for preventing the assertion of the userContextId mismatching.
+    // The default internal stylesheets load from the 'resource:' URL.
+    // Bug 1287607, 1291321 - 'chrome' and 'file' protocols should also be handled in the
+    // same way.
+    if (!/^(chrome|file|resource):\/\//.test(this.href)) {
+      options.window = this.window;
+      options.principal = this.document.nodePrincipal;
+    }
+
+    return fetch(this.href, options).then(({ content }) => {
+      this.text = content;
+      return content;
+    });
+  },
+
+  /**
+   * Protocol method to get the original source (actors) for this
+   * stylesheet if it has uses source maps.
+   */
+  getOriginalSources: function () {
+    if (this._originalSources) {
+      return promise.resolve(this._originalSources);
+    }
+    return this._fetchOriginalSources();
+  },
+
+  /**
+   * Fetch the original sources (actors) for this style sheet using its
+   * source map. If they've already been fetched, returns cached array.
+   *
+   * @return {Promise}
+   *         Promise that resolves with an array of OriginalSourceActors
+   */
+  _fetchOriginalSources: function () {
+    this._clearOriginalSources();
+    this._originalSources = [];
+
+    return this.getSourceMap().then((sourceMap) => {
+      if (!sourceMap) {
+        return null;
+      }
+      for (let url of sourceMap.sources) {
+        let actor = new OriginalSourceActor(url, sourceMap, this);
+
+        this.manage(actor);
+        this._originalSources.push(actor);
+      }
+      return this._originalSources;
+    });
+  },
+
+  /**
+   * Get the SourceMapConsumer for this stylesheet's source map, if
+   * it exists. Saves the consumer for later queries.
+   *
+   * @return {Promise}
+   *         A promise that resolves with a SourceMapConsumer, or null.
+   */
+  getSourceMap: function () {
+    if (this._sourceMap) {
+      return this._sourceMap;
+    }
+    return this._fetchSourceMap();
+  },
+
+  /**
+   * Fetch the source map for this stylesheet.
+   *
+   * @return {Promise}
+   *         A promise that resolves with a SourceMapConsumer, or null.
+   */
+  _fetchSourceMap: function () {
+    let deferred = promise.defer();
+
+    this._getText().then(sheetContent => {
+      let url = this._extractSourceMapUrl(sheetContent);
+      if (!url) {
+        // no source map for this stylesheet
+        deferred.resolve(null);
+        return;
+      }
+
+      url = normalize(url, this.safeHref);
+      let options = {
+        loadFromCache: false,
+        policy: Ci.nsIContentPolicy.TYPE_INTERNAL_STYLESHEET,
+        window: this.window
+      };
+
+      let map = fetch(url, options).then(({content}) => {
+        // Fetching the source map might have failed with a 404 or other. When
+        // this happens, SourceMapConsumer may fail with a JSON.parse error.
+        let consumer;
+        try {
+          consumer = new SourceMapConsumer(content);
+        } catch (e) {
+          deferred.reject(new Error(
+            `Source map at ${url} not found or invalid`));
+          return null;
+        }
+        this._setSourceMapRoot(consumer, url, this.safeHref);
+        this._sourceMap = promise.resolve(consumer);
+
+        deferred.resolve(consumer);
+        return consumer;
+      }, deferred.reject);
+
+      this._sourceMap = map;
+    }, deferred.reject);
+
+    return deferred.promise;
+  },
+
+  /**
+   * Clear and unmanage the original source actors for this stylesheet.
+   */
+  _clearOriginalSources: function () {
+    for (actor in this._originalSources) {
+      this.unmanage(actor);
+    }
+    this._originalSources = null;
+  },
+
+  /**
+   * Sets the source map's sourceRoot to be relative to the source map url.
+   */
+  _setSourceMapRoot: function (aSourceMap, aAbsSourceMapURL, aScriptURL) {
+    if (aScriptURL.startsWith("blob:")) {
+      aScriptURL = aScriptURL.replace("blob:", "");
+    }
+    const base = dirname(
+      aAbsSourceMapURL.startsWith("data:")
+        ? aScriptURL
+        : aAbsSourceMapURL);
+    aSourceMap.sourceRoot = aSourceMap.sourceRoot
+      ? normalize(aSourceMap.sourceRoot, base)
+      : base;
+  },
+
+  /**
+   * Get the source map url specified in the text of a stylesheet.
+   *
+   * @param  {string} content
+   *         The text of the style sheet.
+   * @return {string}
+   *         Url of source map.
+   */
+  _extractSourceMapUrl: function (content) {
+    var matches = /sourceMappingURL\=([^\s\*]*)/.exec(content);
+    if (matches) {
+      return matches[1];
+    }
+    return null;
+  },
+
+  /**
+   * Protocol method that gets the location in the original source of a
+   * line, column pair in this stylesheet, if its source mapped, otherwise
+   * a promise of the same location.
+   */
+  getOriginalLocation: function (line, column) {
+    return this.getSourceMap().then((sourceMap) => {
+      if (sourceMap) {
+        return sourceMap.originalPositionFor({ line: line, column: column });
+      }
+      return {
+        fromSourceMap: false,
+        source: this.href,
+        line: line,
+        column: column
+      };
+    });
+  },
+
+  /**
+   * Protocol method to get the media rules for the stylesheet.
+   */
+  getMediaRules: function () {
+    return this._getMediaRules();
+  },
+
+  /**
+   * Get all the @media rules in this stylesheet.
+   *
+   * @return {promise}
+   *         A promise that resolves with an array of MediaRuleActors.
+   */
+  _getMediaRules: function () {
+    return this.getCSSRules().then((rules) => {
+      let mediaRules = [];
+      for (let i = 0; i < rules.length; i++) {
+        let rule = rules[i];
+        if (rule.type != Ci.nsIDOMCSSRule.MEDIA_RULE) {
+          continue;
+        }
+        let actor = new MediaRuleActor(rule, this);
+        this.manage(actor);
+
+        mediaRules.push(actor);
+      }
+      return mediaRules;
+    });
+  },
+
+  /**
+   * Get the charset of the stylesheet according to the character set rules
+   * defined in <http://www.w3.org/TR/CSS2/syndata.html#charset>.
+   * Note that some of the algorithm is implemented in DevToolsUtils.fetch.
+   */
+  _getCSSCharset: function ()
+  {
+    let sheet = this.rawSheet;
+    if (sheet) {
+      // Do we have a @charset rule in the stylesheet?
+      // step 2 of syndata.html (without the BOM check).
+      if (sheet.cssRules) {
+        let rules = sheet.cssRules;
+        if (rules.length
+            && rules.item(0).type == Ci.nsIDOMCSSRule.CHARSET_RULE) {
+          return rules.item(0).encoding;
+        }
+      }
+
+      // step 3: charset attribute of <link> or <style> element, if it exists
+      if (sheet.ownerNode && sheet.ownerNode.getAttribute) {
+        let linkCharset = sheet.ownerNode.getAttribute("charset");
+        if (linkCharset != null) {
+          return linkCharset;
+        }
+      }
+
+      // step 4 (1 of 2): charset of referring stylesheet.
+      let parentSheet = sheet.parentStyleSheet;
+      if (parentSheet && parentSheet.cssRules &&
+          parentSheet.cssRules[0].type == Ci.nsIDOMCSSRule.CHARSET_RULE) {
+        return parentSheet.cssRules[0].encoding;
+      }
+
+      // step 4 (2 of 2): charset of referring document.
+      if (sheet.ownerNode && sheet.ownerNode.ownerDocument.characterSet) {
+        return sheet.ownerNode.ownerDocument.characterSet;
+      }
+    }
+
+    // step 5: default to utf-8.
+    return "UTF-8";
+  },
+
+  /**
+   * Update the style sheet in place with new text.
+   *
+   * @param  {object} request
+   *         'text' - new text
+   *         'transition' - whether to do CSS transition for change.
+   *         'kind' - either UPDATE_PRESERVING_RULES or UPDATE_GENERAL
+   */
+  update: function (text, transition, kind = UPDATE_GENERAL) {
+    DOMUtils.parseStyleSheet(this.rawSheet, text);
+
+    modifiedStyleSheets.set(this.rawSheet, text);
+
+    this.text = text;
+
+    this._notifyPropertyChanged("ruleCount");
+
+    if (transition) {
+      this._insertTransistionRule(kind);
+    }
+    else {
+      events.emit(this, "style-applied", kind, this);
+    }
+
+    this._getMediaRules().then((rules) => {
+      events.emit(this, "media-rules-changed", rules);
+    });
+  },
+
+  /**
+   * Insert a catch-all transition rule into the document. Set a timeout
+   * to remove the rule after a certain time.
+   */
+  _insertTransistionRule: function (kind) {
+    addPseudoClassLock(this.document.documentElement, TRANSITION_PSEUDO_CLASS);
+
+    // We always add the rule since we've just reset all the rules
+    this.rawSheet.insertRule(TRANSITION_RULE, this.rawSheet.cssRules.length);
+
+    // Set up clean up and commit after transition duration (+buffer)
+    // @see _onTransitionEnd
+    this.window.clearTimeout(this._transitionTimeout);
+    this._transitionTimeout = this.window.setTimeout(this._onTransitionEnd.bind(this, kind),
+                              TRANSITION_DURATION_MS + TRANSITION_BUFFER_MS);
+  },
+
+  /**
+   * This cleans up class and rule added for transition effect and then
+   * notifies that the style has been applied.
+   */
+  _onTransitionEnd: function (kind)
+  {
+    this._transitionTimeout = null;
+    removePseudoClassLock(this.document.documentElement, TRANSITION_PSEUDO_CLASS);
+
+    let index = this.rawSheet.cssRules.length - 1;
+    let rule = this.rawSheet.cssRules[index];
+    if (rule.selectorText == TRANSITION_RULE_SELECTOR) {
+      this.rawSheet.deleteRule(index);
+    }
+
+    events.emit(this, "style-applied", kind, this);
+  }
+});
+
+exports.StyleSheetActor = StyleSheetActor;
+
+/**
+ * Creates a StyleSheetsActor. StyleSheetsActor provides remote access to the
+ * stylesheets of a document.
+ */
+var StyleSheetsActor = protocol.ActorClassWithSpec(styleSheetsSpec, {
+  /**
+   * The window we work with, taken from the parent actor.
+   */
+  get window() {
+    return this.parentActor.window;
+  },
+
+  /**
+   * The current content document of the window we work with.
+   */
+  get document() {
+    return this.window.document;
+  },
+
+  form: function ()
+  {
+    return { actor: this.actorID };
+  },
+
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, null);
+
+    this.parentActor = tabActor;
+  },
+
+  /**
+   * Protocol method for getting a list of StyleSheetActors representing
+   * all the style sheets in this document.
+   */
+  getStyleSheets: Task.async(function* () {
+    // Iframe document can change during load (bug 1171919). Track their windows
+    // instead.
+    let windows = [this.window];
+    let actors = [];
+
+    for (let win of windows) {
+      let sheets = yield this._addStyleSheets(win);
+      actors = actors.concat(sheets);
+
+      // Recursively handle style sheets of the documents in iframes.
+      for (let iframe of win.document.querySelectorAll("iframe, browser, frame")) {
+        if (iframe.contentDocument && iframe.contentWindow) {
+          // Sometimes, iframes don't have any document, like the
+          // one that are over deeply nested (bug 285395)
+          windows.push(iframe.contentWindow);
+        }
+      }
+    }
+    return actors;
+  }),
+
+  /**
+   * Check if we should be showing this stylesheet.
+   *
+   * @param {Document} doc
+   *        Document for which we're checking
+   * @param {DOMCSSStyleSheet} sheet
+   *        Stylesheet we're interested in
+   *
+   * @return boolean
+   *         Whether the stylesheet should be listed.
+   */
+  _shouldListSheet: function (doc, sheet) {
+    // Special case about:PreferenceStyleSheet, as it is generated on the
+    // fly and the URI is not registered with the about: handler.
+    // https://bugzilla.mozilla.org/show_bug.cgi?id=935803#c37
+    if (sheet.href && sheet.href.toLowerCase() == "about:preferencestylesheet") {
+      return false;
+    }
+
+    return true;
+  },
+
+  /**
+   * Add all the stylesheets for the document in this window to the map and
+   * create an actor for each one if not already created.
+   *
+   * @param {Window} win
+   *        Window for which to add stylesheets
+   *
+   * @return {Promise}
+   *         Promise that resolves to an array of StyleSheetActors
+   */
+  _addStyleSheets: function (win)
+  {
+    return Task.spawn(function* () {
+      let doc = win.document;
+      // readyState can be uninitialized if an iframe has just been created but
+      // it has not started to load yet.
+      if (doc.readyState === "loading" || doc.readyState === "uninitialized") {
+        // Wait for the document to load first.
+        yield listenOnce(win, "DOMContentLoaded", true);
+
+        // Make sure we have the actual document for this window. If the
+        // readyState was initially uninitialized, the initial dummy document
+        // was replaced with the actual document (bug 1171919).
+        doc = win.document;
+      }
+
+      let isChrome = Services.scriptSecurityManager.isSystemPrincipal(doc.nodePrincipal);
+      let styleSheets = isChrome ? DOMUtils.getAllStyleSheets(doc) : doc.styleSheets;
+      let actors = [];
+      for (let i = 0; i < styleSheets.length; i++) {
+        let sheet = styleSheets[i];
+        if (!this._shouldListSheet(doc, sheet)) {
+          continue;
+        }
+
+        let actor = this.parentActor.createStyleSheetActor(sheet);
+        actors.push(actor);
+
+        // Get all sheets, including imported ones
+        let imports = yield this._getImported(doc, actor);
+        actors = actors.concat(imports);
+      }
+      return actors;
+    }.bind(this));
+  },
+
+  /**
+   * Get all the stylesheets @imported from a stylesheet.
+   *
+   * @param  {Document} doc
+   *         The document including the stylesheet
+   * @param  {DOMStyleSheet} styleSheet
+   *         Style sheet to search
+   * @return {Promise}
+   *         A promise that resolves with an array of StyleSheetActors
+   */
+  _getImported: function (doc, styleSheet) {
+    return Task.spawn(function* () {
+      let rules = yield styleSheet.getCSSRules();
+      let imported = [];
+
+      for (let i = 0; i < rules.length; i++) {
+        let rule = rules[i];
+        if (rule.type == Ci.nsIDOMCSSRule.IMPORT_RULE) {
+          // Associated styleSheet may be null if it has already been seen due
+          // to duplicate @imports for the same URL.
+          if (!rule.styleSheet || !this._shouldListSheet(doc, rule.styleSheet)) {
+            continue;
+          }
+          let actor = this.parentActor.createStyleSheetActor(rule.styleSheet);
+          imported.push(actor);
+
+          // recurse imports in this stylesheet as well
+          let children = yield this._getImported(doc, actor);
+          imported = imported.concat(children);
+        }
+        else if (rule.type != Ci.nsIDOMCSSRule.CHARSET_RULE) {
+          // @import rules must precede all others except @charset
+          break;
+        }
+      }
+
+      return imported;
+    }.bind(this));
+  },
+
+
+  /**
+   * Create a new style sheet in the document with the given text.
+   * Return an actor for it.
+   *
+   * @param  {object} request
+   *         Debugging protocol request object, with 'text property'
+   * @return {object}
+   *         Object with 'styelSheet' property for form on new actor.
+   */
+  addStyleSheet: function (text) {
+    let parent = this.document.documentElement;
+    let style = this.document.createElementNS("http://www.w3.org/1999/xhtml", "style");
+    style.setAttribute("type", "text/css");
+
+    if (text) {
+      style.appendChild(this.document.createTextNode(text));
+    }
+    parent.appendChild(style);
+
+    let actor = this.parentActor.createStyleSheetActor(style.sheet);
+    return actor;
+  }
+});
+
+exports.StyleSheetsActor = StyleSheetsActor;
+
+/**
+ * Normalize multiple relative paths towards the base paths on the right.
+ */
+function normalize(...aURLs) {
+  let base = Services.io.newURI(aURLs.pop(), null, null);
+  let url;
+  while ((url = aURLs.pop())) {
+    base = Services.io.newURI(url, null, base);
+  }
+  return base.spec;
+}
+
+function dirname(aPath) {
+  return Services.io.newURI(
+    ".", null, Services.io.newURI(aPath, null, null)).spec;
+}
diff --git a/devtools/server/actors/timeline.js b/devtools/server/actors/timeline.js
new file mode 100644
index 000000000..221454144
--- /dev/null
+++ b/devtools/server/actors/timeline.js
@@ -0,0 +1,98 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+/**
+ * Many Gecko operations (painting, reflows, restyle, ...) can be tracked
+ * in real time. A marker is a representation of one operation. A marker
+ * has a name, start and end timestamps. Markers are stored in docShells.
+ *
+ * This actor exposes this tracking mechanism to the devtools protocol.
+ * Most of the logic is handled in devtools/server/performance/timeline.js
+ * This just wraps that module up and exposes it via RDP.
+ *
+ * For more documentation:
+ * @see devtools/server/performance/timeline.js
+ */
+
+const protocol = require("devtools/shared/protocol");
+const { Option, RetVal } = protocol;
+const { actorBridgeWithSpec } = require("devtools/server/actors/common");
+const { Timeline } = require("devtools/server/performance/timeline");
+const { timelineSpec } = require("devtools/shared/specs/timeline");
+const events = require("sdk/event/core");
+
+/**
+ * The timeline actor pops and forwards timeline markers registered in docshells.
+ */
+var TimelineActor = exports.TimelineActor = protocol.ActorClassWithSpec(timelineSpec, {
+  /**
+   * Initializes this actor with the provided connection and tab actor.
+   */
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.tabActor = tabActor;
+    this.bridge = new Timeline(tabActor);
+
+    this._onTimelineEvent = this._onTimelineEvent.bind(this);
+    events.on(this.bridge, "*", this._onTimelineEvent);
+  },
+
+  /**
+   * The timeline actor is the first (and last) in its hierarchy to use
+   * protocol.js so it doesn't have a parent protocol actor that takes care of
+   * its lifetime. So it needs a disconnect method to cleanup.
+   */
+  disconnect: function () {
+    this.destroy();
+  },
+
+  /**
+   * Destroys this actor, stopping recording first.
+   */
+  destroy: function () {
+    events.off(this.bridge, "*", this._onTimelineEvent);
+    this.bridge.destroy();
+    this.bridge = null;
+    this.tabActor = null;
+    protocol.Actor.prototype.destroy.call(this);
+  },
+
+  /**
+   * Propagate events from the Timeline module over RDP if the event is defined
+   * here.
+   */
+  _onTimelineEvent: function (eventName, ...args) {
+    events.emit(this, eventName, ...args);
+  },
+
+  isRecording: actorBridgeWithSpec("isRecording", {
+    request: {},
+    response: {
+      value: RetVal("boolean")
+    }
+  }),
+
+  start: actorBridgeWithSpec("start", {
+    request: {
+      withMarkers: Option(0, "boolean"),
+      withTicks: Option(0, "boolean"),
+      withMemory: Option(0, "boolean"),
+      withFrames: Option(0, "boolean"),
+      withGCEvents: Option(0, "boolean"),
+      withDocLoadingEvents: Option(0, "boolean")
+    },
+    response: {
+      value: RetVal("number")
+    }
+  }),
+
+  stop: actorBridgeWithSpec("stop", {
+    response: {
+      // Set as possibly nullable due to the end time possibly being
+      // undefined during destruction
+      value: RetVal("nullable:number")
+    }
+  }),
+});
diff --git a/devtools/server/actors/utils/TabSources.js b/devtools/server/actors/utils/TabSources.js
new file mode 100644
index 000000000..56e862939
--- /dev/null
+++ b/devtools/server/actors/utils/TabSources.js
@@ -0,0 +1,833 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Ci, Cu } = require("chrome");
+const DevToolsUtils = require("devtools/shared/DevToolsUtils");
+const { assert, fetch } = DevToolsUtils;
+const EventEmitter = require("devtools/shared/event-emitter");
+const { OriginalLocation, GeneratedLocation } = require("devtools/server/actors/common");
+const { resolve } = require("promise");
+const { joinURI } = require("devtools/shared/path");
+
+loader.lazyRequireGetter(this, "SourceActor", "devtools/server/actors/source", true);
+loader.lazyRequireGetter(this, "isEvalSource", "devtools/server/actors/source", true);
+loader.lazyRequireGetter(this, "SourceMapConsumer", "source-map", true);
+loader.lazyRequireGetter(this, "SourceMapGenerator", "source-map", true);
+
+/**
+ * Manages the sources for a thread. Handles source maps, locations in the
+ * sources, etc for ThreadActors.
+ */
+function TabSources(threadActor, allowSourceFn = () => true) {
+  EventEmitter.decorate(this);
+
+  this._thread = threadActor;
+  this._useSourceMaps = true;
+  this._autoBlackBox = true;
+  this._anonSourceMapId = 1;
+  this.allowSource = source => {
+    return !isHiddenSource(source) && allowSourceFn(source);
+  };
+
+  this.blackBoxedSources = new Set();
+  this.prettyPrintedSources = new Map();
+  this.neverAutoBlackBoxSources = new Set();
+
+  // generated Debugger.Source -> promise of SourceMapConsumer
+  this._sourceMaps = new Map();
+  // sourceMapURL -> promise of SourceMapConsumer
+  this._sourceMapCache = Object.create(null);
+  // Debugger.Source -> SourceActor
+  this._sourceActors = new Map();
+  // url -> SourceActor
+  this._sourceMappedSourceActors = Object.create(null);
+}
+
+/**
+ * Matches strings of the form "foo.min.js" or "foo-min.js", etc. If the regular
+ * expression matches, we can be fairly sure that the source is minified, and
+ * treat it as such.
+ */
+const MINIFIED_SOURCE_REGEXP = /\bmin\.js$/;
+
+TabSources.prototype = {
+  /**
+   * Update preferences and clear out existing sources
+   */
+  setOptions: function (options) {
+    let shouldReset = false;
+
+    if ("useSourceMaps" in options) {
+      shouldReset = true;
+      this._useSourceMaps = options.useSourceMaps;
+    }
+
+    if ("autoBlackBox" in options) {
+      shouldReset = true;
+      this._autoBlackBox = options.autoBlackBox;
+    }
+
+    if (shouldReset) {
+      this.reset();
+    }
+  },
+
+  /**
+   * Clear existing sources so they are recreated on the next access.
+   *
+   * @param Object opts
+   *        Specify { sourceMaps: true } if you also want to clear
+   *        the source map cache (usually done on reload).
+   */
+  reset: function (opts = {}) {
+    this._sourceActors = new Map();
+    this._sourceMaps = new Map();
+    this._sourceMappedSourceActors = Object.create(null);
+
+    if (opts.sourceMaps) {
+      this._sourceMapCache = Object.create(null);
+    }
+  },
+
+  /**
+   * Return the source actor representing the `source` (or
+   * `originalUrl`), creating one if none exists already. May return
+   * null if the source is disallowed.
+   *
+   * @param Debugger.Source source
+   *        The source to make an actor for
+   * @param String originalUrl
+   *        The original source URL of a sourcemapped source
+   * @param optional Debguger.Source generatedSource
+   *        The generated source that introduced this source via source map,
+   *        if any.
+   * @param optional String contentType
+   *        The content type of the source, if immediately available.
+   * @returns a SourceActor representing the source or null.
+   */
+  source: function ({ source, originalUrl, generatedSource,
+                       isInlineSource, contentType }) {
+    assert(source || (originalUrl && generatedSource),
+           "TabSources.prototype.source needs an originalUrl or a source");
+
+    if (source) {
+      // If a source is passed, we are creating an actor for a real
+      // source, which may or may not be sourcemapped.
+
+      if (!this.allowSource(source)) {
+        return null;
+      }
+
+      // It's a hack, but inline HTML scripts each have real sources,
+      // but we want to represent all of them as one source as the
+      // HTML page. The actor representing this fake HTML source is
+      // stored in this array, which always has a URL, so check it
+      // first.
+      if (source.url in this._sourceMappedSourceActors) {
+        return this._sourceMappedSourceActors[source.url];
+      }
+
+      if (isInlineSource) {
+        // If it's an inline source, the fake HTML source hasn't been
+        // created yet (would have returned above), so flip this source
+        // into a sourcemapped state by giving it an `originalUrl` which
+        // is the HTML url.
+        originalUrl = source.url;
+        source = null;
+      }
+      else if (this._sourceActors.has(source)) {
+        return this._sourceActors.get(source);
+      }
+    }
+    else if (originalUrl) {
+      // Not all "original" scripts are distinctly separate from the
+      // generated script. Pretty-printed sources have a sourcemap for
+      // themselves, so we need to make sure there a real source
+      // doesn't already exist with this URL.
+      for (let [source, actor] of this._sourceActors) {
+        if (source.url === originalUrl) {
+          return actor;
+        }
+      }
+
+      if (originalUrl in this._sourceMappedSourceActors) {
+        return this._sourceMappedSourceActors[originalUrl];
+      }
+    }
+
+    let actor = new SourceActor({
+      thread: this._thread,
+      source: source,
+      originalUrl: originalUrl,
+      generatedSource: generatedSource,
+      isInlineSource: isInlineSource,
+      contentType: contentType
+    });
+
+    let sourceActorStore = this._thread.sourceActorStore;
+    var id = sourceActorStore.getReusableActorId(source, originalUrl);
+    if (id) {
+      actor.actorID = id;
+    }
+
+    this._thread.threadLifetimePool.addActor(actor);
+    sourceActorStore.setReusableActorId(source, originalUrl, actor.actorID);
+
+    if (this._autoBlackBox &&
+        !this.neverAutoBlackBoxSources.has(actor.url) &&
+        this._isMinifiedURL(actor.url)) {
+
+      this.blackBox(actor.url);
+      this.neverAutoBlackBoxSources.add(actor.url);
+    }
+
+    if (source) {
+      this._sourceActors.set(source, actor);
+    }
+    else {
+      this._sourceMappedSourceActors[originalUrl] = actor;
+    }
+
+    this._emitNewSource(actor);
+    return actor;
+  },
+
+  _emitNewSource: function (actor) {
+    if (!actor.source) {
+      // Always notify if we don't have a source because that means
+      // it's something that has been sourcemapped, or it represents
+      // the HTML file that contains inline sources.
+      this.emit("newSource", actor);
+    }
+    else {
+      // If sourcemapping is enabled and a source has sourcemaps, we
+      // create `SourceActor` instances for both the original and
+      // generated sources. The source actors for the generated
+      // sources are only for internal use, however; breakpoints are
+      // managed by these internal actors. We only want to notify the
+      // user of the original sources though, so if the actor has a
+      // `Debugger.Source` instance and a valid source map (meaning
+      // it's a generated source), don't send the notification.
+      this.fetchSourceMap(actor.source).then(map => {
+        if (!map) {
+          this.emit("newSource", actor);
+        }
+      });
+    }
+  },
+
+  getSourceActor: function (source) {
+    if (source.url in this._sourceMappedSourceActors) {
+      return this._sourceMappedSourceActors[source.url];
+    }
+
+    if (this._sourceActors.has(source)) {
+      return this._sourceActors.get(source);
+    }
+
+    throw new Error("getSource: could not find source actor for " +
+                    (source.url || "source"));
+  },
+
+  getSourceActorByURL: function (url) {
+    if (url) {
+      for (let [source, actor] of this._sourceActors) {
+        if (source.url === url) {
+          return actor;
+        }
+      }
+
+      if (url in this._sourceMappedSourceActors) {
+        return this._sourceMappedSourceActors[url];
+      }
+    }
+
+    throw new Error("getSourceActorByURL: could not find source for " + url);
+    return null;
+  },
+
+  /**
+   * Returns true if the URL likely points to a minified resource, false
+   * otherwise.
+   *
+   * @param String aURL
+   *        The URL to test.
+   * @returns Boolean
+   */
+  _isMinifiedURL: function (aURL) {
+    if (!aURL) {
+      return false;
+    }
+
+    try {
+      let url = new URL(aURL);
+      let pathname = url.pathname;
+      return MINIFIED_SOURCE_REGEXP.test(pathname.slice(pathname.lastIndexOf("/") + 1));
+    } catch (e) {
+      // Not a valid URL so don't try to parse out the filename, just test the
+      // whole thing with the minified source regexp.
+      return MINIFIED_SOURCE_REGEXP.test(aURL);
+    }
+  },
+
+  /**
+   * Create a source actor representing this source. This ignores
+   * source mapping and always returns an actor representing this real
+   * source. Use `createSourceActors` if you want to respect source maps.
+   *
+   * @param Debugger.Source aSource
+   *        The source instance to create an actor for.
+   * @returns SourceActor
+   */
+  createNonSourceMappedActor: function (aSource) {
+    // Don't use getSourceURL because we don't want to consider the
+    // displayURL property if it's an eval source. We only want to
+    // consider real URLs, otherwise if there is a URL but it's
+    // invalid the code below will not set the content type, and we
+    // will later try to fetch the contents of the URL to figure out
+    // the content type, but it's a made up URL for eval sources.
+    let url = isEvalSource(aSource) ? null : aSource.url;
+    let spec = { source: aSource };
+
+    // XXX bug 915433: We can't rely on Debugger.Source.prototype.text
+    // if the source is an HTML-embedded <script> tag. Since we don't
+    // have an API implemented to detect whether this is the case, we
+    // need to be conservative and only treat valid js files as real
+    // sources. Otherwise, use the `originalUrl` property to treat it
+    // as an HTML source that manages multiple inline sources.
+
+    // Assume the source is inline if the element that introduced it is not a
+    // script element, or does not have a src attribute.
+    let element = aSource.element ? aSource.element.unsafeDereference() : null;
+    if (element && (element.tagName !== "SCRIPT" || !element.hasAttribute("src"))) {
+      spec.isInlineSource = true;
+    } else if (aSource.introductionType === "wasm") {
+      // Wasm sources are not JavaScript. Give them their own content-type.
+      spec.contentType = "text/wasm";
+    } else {
+      if (url) {
+        // There are a few special URLs that we know are JavaScript:
+        // inline `javascript:` and code coming from the console
+        if (url.indexOf("Scratchpad/") === 0 ||
+            url.indexOf("javascript:") === 0 ||
+            url === "debugger eval code") {
+          spec.contentType = "text/javascript";
+        } else {
+          try {
+            let pathname = new URL(url).pathname;
+            let filename = pathname.slice(pathname.lastIndexOf("/") + 1);
+            let index = filename.lastIndexOf(".");
+            let extension = index >= 0 ? filename.slice(index + 1) : "";
+            if (extension === "xml") {
+              // XUL inline scripts may not correctly have the
+              // `source.element` property, so do a blunt check here if
+              // it's an xml page.
+              spec.isInlineSource = true;
+            }
+            else if (extension === "js") {
+              spec.contentType = "text/javascript";
+            }
+          } catch (e) {
+            // This only needs to be here because URL is not yet exposed to
+            // workers. (BUG 1258892)
+            const filename = url;
+            const index = filename.lastIndexOf(".");
+            const extension = index >= 0 ? filename.slice(index + 1) : "";
+            if (extension === "js") {
+              spec.contentType = "text/javascript";
+            }
+          }
+        }
+      }
+      else {
+        // Assume the content is javascript if there's no URL
+        spec.contentType = "text/javascript";
+      }
+    }
+
+    return this.source(spec);
+  },
+
+  /**
+   * This is an internal function that returns a promise of an array
+   * of source actors representing all the source mapped sources of
+   * `aSource`, or `null` if the source is not sourcemapped or
+   * sourcemapping is disabled. Users should call `createSourceActors`
+   * instead of this.
+   *
+   * @param Debugger.Source aSource
+   *        The source instance to create actors for.
+   * @return Promise of an array of source actors
+   */
+  _createSourceMappedActors: function (aSource) {
+    if (!this._useSourceMaps || !aSource.sourceMapURL) {
+      return resolve(null);
+    }
+
+    return this.fetchSourceMap(aSource)
+      .then(map => {
+        if (map) {
+          return map.sources.map(s => {
+            return this.source({ originalUrl: s, generatedSource: aSource });
+          }).filter(isNotNull);
+        }
+        return null;
+      });
+  },
+
+  /**
+   * Creates the source actors representing the appropriate sources
+   * of `aSource`. If sourcemapped, returns actors for all of the original
+   * sources, otherwise returns a 1-element array with the actor for
+   * `aSource`.
+   *
+   * @param Debugger.Source aSource
+   *        The source instance to create actors for.
+   * @param Promise of an array of source actors
+   */
+  createSourceActors: function (aSource) {
+    return this._createSourceMappedActors(aSource).then(actors => {
+      let actor = this.createNonSourceMappedActor(aSource);
+      return (actors || [actor]).filter(isNotNull);
+    });
+  },
+
+  /**
+   * Return a promise of a SourceMapConsumer for the source map for
+   * `aSource`; if we already have such a promise extant, return that.
+   * This will fetch the source map if we don't have a cached object
+   * and source maps are enabled (see `_fetchSourceMap`).
+   *
+   * @param Debugger.Source aSource
+   *        The source instance to get sourcemaps for.
+   * @return Promise of a SourceMapConsumer
+   */
+  fetchSourceMap: function (aSource) {
+    if (!this._useSourceMaps) {
+      return resolve(null);
+    }
+    else if (this._sourceMaps.has(aSource)) {
+      return this._sourceMaps.get(aSource);
+    }
+    else if (!aSource || !aSource.sourceMapURL) {
+      return resolve(null);
+    }
+
+    let sourceMapURL = aSource.sourceMapURL;
+    if (aSource.url) {
+      sourceMapURL = joinURI(aSource.url, sourceMapURL);
+    }
+    let result = this._fetchSourceMap(sourceMapURL, aSource.url);
+
+    // The promises in `_sourceMaps` must be the exact same instances
+    // as returned by `_fetchSourceMap` for `clearSourceMapCache` to
+    // work.
+    this._sourceMaps.set(aSource, result);
+    return result;
+  },
+
+  /**
+   * Return a promise of a SourceMapConsumer for the source map for
+   * `aSource`. The resolved result may be null if the source does not
+   * have a source map or source maps are disabled.
+   */
+  getSourceMap: function (aSource) {
+    return resolve(this._sourceMaps.get(aSource));
+  },
+
+  /**
+   * Set a SourceMapConsumer for the source map for
+   * |aSource|.
+   */
+  setSourceMap: function (aSource, aMap) {
+    this._sourceMaps.set(aSource, resolve(aMap));
+  },
+
+  /**
+   * Return a promise of a SourceMapConsumer for the source map located at
+   * |aAbsSourceMapURL|, which must be absolute. If there is already such a
+   * promise extant, return it. This will not fetch if source maps are
+   * disabled.
+   *
+   * @param string aAbsSourceMapURL
+   *        The source map URL, in absolute form, not relative.
+   * @param string aScriptURL
+   *        When the source map URL is a data URI, there is no sourceRoot on the
+   *        source map, and the source map's sources are relative, we resolve
+   *        them from aScriptURL.
+   */
+  _fetchSourceMap: function (aAbsSourceMapURL, aSourceURL) {
+    assert(this._useSourceMaps,
+           "Cannot fetch sourcemaps if they are disabled");
+
+    if (this._sourceMapCache[aAbsSourceMapURL]) {
+      return this._sourceMapCache[aAbsSourceMapURL];
+    }
+
+    let fetching = fetch(aAbsSourceMapURL, { loadFromCache: false })
+      .then(({ content }) => {
+        let map = new SourceMapConsumer(content);
+        this._setSourceMapRoot(map, aAbsSourceMapURL, aSourceURL);
+        return map;
+      })
+      .then(null, error => {
+        if (!DevToolsUtils.reportingDisabled) {
+          DevToolsUtils.reportException("TabSources.prototype._fetchSourceMap", error);
+        }
+        return null;
+      });
+    this._sourceMapCache[aAbsSourceMapURL] = fetching;
+    return fetching;
+  },
+
+  /**
+   * Sets the source map's sourceRoot to be relative to the source map url.
+   */
+  _setSourceMapRoot: function (aSourceMap, aAbsSourceMapURL, aScriptURL) {
+    // No need to do this fiddling if we won't be fetching any sources over the
+    // wire.
+    if (aSourceMap.hasContentsOfAllSources()) {
+      return;
+    }
+
+    const base = this._dirname(
+      aAbsSourceMapURL.indexOf("data:") === 0
+        ? aScriptURL
+        : aAbsSourceMapURL);
+    aSourceMap.sourceRoot = aSourceMap.sourceRoot
+      ? joinURI(base, aSourceMap.sourceRoot)
+      : base;
+  },
+
+  _dirname: function (aPath) {
+    let url = new URL(aPath);
+    let href = url.href;
+    return href.slice(0, href.lastIndexOf("/"));
+  },
+
+  /**
+   * Clears the source map cache. Source maps are cached by URL so
+   * they can be reused across separate Debugger instances (once in
+   * this cache, they will never be reparsed again). They are
+   * also cached by Debugger.Source objects for usefulness. By default
+   * this just removes the Debugger.Source cache, but you can remove
+   * the lower-level URL cache with the `hard` option.
+   *
+   * @param aSourceMapURL string
+   *        The source map URL to uncache
+   * @param opts object
+   *        An object with the following properties:
+   *        - hard: Also remove the lower-level URL cache, which will
+   *          make us completely forget about the source map.
+   */
+  clearSourceMapCache: function (aSourceMapURL, opts = { hard: false }) {
+    let oldSm = this._sourceMapCache[aSourceMapURL];
+
+    if (opts.hard) {
+      delete this._sourceMapCache[aSourceMapURL];
+    }
+
+    if (oldSm) {
+      // Clear out the current cache so all sources will get the new one
+      for (let [source, sm] of this._sourceMaps.entries()) {
+        if (sm === oldSm) {
+          this._sourceMaps.delete(source);
+        }
+      }
+    }
+  },
+
+  /*
+   * Forcefully change the source map of a source, changing the
+   * sourceMapURL and installing the source map in the cache. This is
+   * necessary to expose changes across Debugger instances
+   * (pretty-printing is the use case). Generate a random url if one
+   * isn't specified, allowing you to set "anonymous" source maps.
+   *
+   * @param aSource Debugger.Source
+   *        The source to change the sourceMapURL property
+   * @param aUrl string
+   *        The source map URL (optional)
+   * @param aMap SourceMapConsumer
+   *        The source map instance
+   */
+  setSourceMapHard: function (aSource, aUrl, aMap) {
+    let url = aUrl;
+    if (!url) {
+      // This is a littly hacky, but we want to forcefully set a
+      // sourcemap regardless of sourcemap settings. We want to
+      // literally change the sourceMapURL so that all debuggers will
+      // get this and pretty-printing will Just Work (Debugger.Source
+      // instances are per-debugger, so we can't key off that). To
+      // avoid tons of work serializing the sourcemap into a data url,
+      // just make a fake URL and stick the sourcemap there.
+      url = "internal://sourcemap" + (this._anonSourceMapId++) + "/";
+    }
+    aSource.sourceMapURL = url;
+
+    // Forcefully set the sourcemap cache. This will be used even if
+    // sourcemaps are disabled.
+    this._sourceMapCache[url] = resolve(aMap);
+    this.emit("updatedSource", this.getSourceActor(aSource));
+  },
+
+  /**
+   * Return the non-source-mapped location of the given Debugger.Frame. If the
+   * frame does not have a script, the location's properties are all null.
+   *
+   * @param Debugger.Frame aFrame
+   *        The frame whose location we are getting.
+   * @returns Object
+   *          Returns an object of the form { source, line, column }
+   */
+  getFrameLocation: function (aFrame) {
+    if (!aFrame || !aFrame.script) {
+      return new GeneratedLocation();
+    }
+    let {lineNumber, columnNumber} =
+        aFrame.script.getOffsetLocation(aFrame.offset);
+    return new GeneratedLocation(
+      this.createNonSourceMappedActor(aFrame.script.source),
+      lineNumber,
+      columnNumber
+    );
+  },
+
+  /**
+   * Returns a promise of the location in the original source if the source is
+   * source mapped, otherwise a promise of the same location. This can
+   * be called with a source from *any* Debugger instance and we make
+   * sure to that it works properly, reusing source maps if already
+   * fetched. Use this from any actor that needs sourcemapping.
+   */
+  getOriginalLocation: function (generatedLocation) {
+    let {
+      generatedSourceActor,
+      generatedLine,
+      generatedColumn
+    } = generatedLocation;
+    let source = generatedSourceActor.source;
+    let url = source ? source.url : generatedSourceActor._originalUrl;
+
+    // In certain scenarios the source map may have not been fetched
+    // yet (or at least tied to this Debugger.Source instance), so use
+    // `fetchSourceMap` instead of `getSourceMap`. This allows this
+    // function to be called from anywere (across debuggers) and it
+    // should just automatically work.
+    return this.fetchSourceMap(source).then(map => {
+      if (map) {
+        let {
+          source: originalUrl,
+          line: originalLine,
+          column: originalColumn,
+          name: originalName
+        } = map.originalPositionFor({
+          line: generatedLine,
+          column: generatedColumn == null ? Infinity : generatedColumn
+        });
+
+        // Since the `Debugger.Source` instance may come from a
+        // different `Debugger` instance (any actor can call this
+        // method), we can't rely on any of the source discovery
+        // setup (`_discoverSources`, etc) to have been run yet. So
+        // we have to assume that the actor may not already exist,
+        // and we might need to create it, so use `source` and give
+        // it the required parameters for a sourcemapped source.
+        return new OriginalLocation(
+          originalUrl ? this.source({
+            originalUrl: originalUrl,
+            generatedSource: source
+          }) : null,
+          originalLine,
+          originalColumn,
+          originalName
+        );
+      }
+
+      // No source map
+      return OriginalLocation.fromGeneratedLocation(generatedLocation);
+    });
+  },
+
+  getAllGeneratedLocations: function (originalLocation) {
+    let {
+      originalSourceActor,
+      originalLine,
+      originalColumn
+    } = originalLocation;
+
+    let source = (originalSourceActor.source ||
+                  originalSourceActor.generatedSource);
+
+    return this.fetchSourceMap(source).then((map) => {
+      if (map) {
+        map.computeColumnSpans();
+
+        return map.allGeneratedPositionsFor({
+          source: originalSourceActor.url,
+          line: originalLine,
+          column: originalColumn
+        }).map(({ line, column, lastColumn }) => {
+          return new GeneratedLocation(
+            this.createNonSourceMappedActor(source),
+            line,
+            column,
+            lastColumn
+          );
+        });
+      }
+
+      return [GeneratedLocation.fromOriginalLocation(originalLocation)];
+    });
+  },
+
+
+  /**
+   * Returns a promise of the location in the generated source corresponding to
+   * the original source and line given.
+   *
+   * When we pass a script S representing generated code to `sourceMap`,
+   * above, that returns a promise P. The process of resolving P populates
+   * the tables this function uses; thus, it won't know that S's original
+   * source URLs map to S until P is resolved.
+   */
+  getGeneratedLocation: function (originalLocation) {
+    let { originalSourceActor } = originalLocation;
+
+    // Both original sources and normal sources could have sourcemaps,
+    // because normal sources can be pretty-printed which generates a
+    // sourcemap for itself. Check both of the source properties to make it work
+    // for both kinds of sources.
+    let source = originalSourceActor.source || originalSourceActor.generatedSource;
+
+    // See comment about `fetchSourceMap` in `getOriginalLocation`.
+    return this.fetchSourceMap(source).then((map) => {
+      if (map) {
+        let {
+          originalLine,
+          originalColumn
+        } = originalLocation;
+
+        let {
+          line: generatedLine,
+          column: generatedColumn
+        } = map.generatedPositionFor({
+          source: originalSourceActor.url,
+          line: originalLine,
+          column: originalColumn == null ? 0 : originalColumn,
+          bias: SourceMapConsumer.LEAST_UPPER_BOUND
+        });
+
+        return new GeneratedLocation(
+          this.createNonSourceMappedActor(source),
+          generatedLine,
+          generatedColumn
+        );
+      }
+
+      return GeneratedLocation.fromOriginalLocation(originalLocation);
+    });
+  },
+
+  /**
+   * Returns true if URL for the given source is black boxed.
+   *
+   * @param aURL String
+   *        The URL of the source which we are checking whether it is black
+   *        boxed or not.
+   */
+  isBlackBoxed: function (aURL) {
+    return this.blackBoxedSources.has(aURL);
+  },
+
+  /**
+   * Add the given source URL to the set of sources that are black boxed.
+   *
+   * @param aURL String
+   *        The URL of the source which we are black boxing.
+   */
+  blackBox: function (aURL) {
+    this.blackBoxedSources.add(aURL);
+  },
+
+  /**
+   * Remove the given source URL to the set of sources that are black boxed.
+   *
+   * @param aURL String
+   *        The URL of the source which we are no longer black boxing.
+   */
+  unblackBox: function (aURL) {
+    this.blackBoxedSources.delete(aURL);
+  },
+
+  /**
+   * Returns true if the given URL is pretty printed.
+   *
+   * @param aURL String
+   *        The URL of the source that might be pretty printed.
+   */
+  isPrettyPrinted: function (aURL) {
+    return this.prettyPrintedSources.has(aURL);
+  },
+
+  /**
+   * Add the given URL to the set of sources that are pretty printed.
+   *
+   * @param aURL String
+   *        The URL of the source to be pretty printed.
+   */
+  prettyPrint: function (aURL, aIndent) {
+    this.prettyPrintedSources.set(aURL, aIndent);
+  },
+
+  /**
+   * Return the indent the given URL was pretty printed by.
+   */
+  prettyPrintIndent: function (aURL) {
+    return this.prettyPrintedSources.get(aURL);
+  },
+
+  /**
+   * Remove the given URL from the set of sources that are pretty printed.
+   *
+   * @param aURL String
+   *        The URL of the source that is no longer pretty printed.
+   */
+  disablePrettyPrint: function (aURL) {
+    this.prettyPrintedSources.delete(aURL);
+  },
+
+  iter: function () {
+    let actors = Object.keys(this._sourceMappedSourceActors).map(k => {
+      return this._sourceMappedSourceActors[k];
+    });
+    for (let actor of this._sourceActors.values()) {
+      if (!this._sourceMaps.has(actor.source)) {
+        actors.push(actor);
+      }
+    }
+    return actors;
+  }
+};
+
+/*
+ * Checks if a source should never be displayed to the user because
+ * it's either internal or we don't support in the UI yet.
+ */
+function isHiddenSource(aSource) {
+  // Ignore the internal Function.prototype script
+  return aSource.text === "() {\n}";
+}
+
+/**
+ * Returns true if its argument is not null.
+ */
+function isNotNull(aThing) {
+  return aThing !== null;
+}
+
+exports.TabSources = TabSources;
+exports.isHiddenSource = isHiddenSource;
diff --git a/devtools/server/actors/utils/actor-registry-utils.js b/devtools/server/actors/utils/actor-registry-utils.js
new file mode 100644
index 000000000..5866827e1
--- /dev/null
+++ b/devtools/server/actors/utils/actor-registry-utils.js
@@ -0,0 +1,78 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { Cu, CC, Ci, Cc } = require("chrome");
+
+const { DebuggerServer } = require("devtools/server/main");
+const promise = require("promise");
+
+/**
+ * Support for actor registration. Main used by ActorRegistryActor
+ * for dynamic registration of new actors.
+ *
+ * @param sourceText {String} Source of the actor implementation
+ * @param fileName {String} URL of the actor module (for proper stack traces)
+ * @param options {Object} Configuration object
+ */
+exports.registerActor = function (sourceText, fileName, options) {
+  // Register in the current process
+  exports.registerActorInCurrentProcess(sourceText, fileName, options);
+  // Register in any child processes
+  return DebuggerServer.setupInChild({
+    module: "devtools/server/actors/utils/actor-registry-utils",
+    setupChild: "registerActorInCurrentProcess",
+    args: [sourceText, fileName, options],
+    waitForEval: true
+  });
+};
+
+exports.registerActorInCurrentProcess = function (sourceText, fileName, options) {
+  const principal = CC("@mozilla.org/systemprincipal;1", "nsIPrincipal")();
+  const sandbox = Cu.Sandbox(principal);
+  sandbox.exports = {};
+  sandbox.require = require;
+
+  Cu.evalInSandbox(sourceText, sandbox, "1.8", fileName, 1);
+
+  let { prefix, constructor, type } = options;
+
+  if (type.global && !DebuggerServer.globalActorFactories.hasOwnProperty(prefix)) {
+    DebuggerServer.addGlobalActor({
+      constructorName: constructor,
+      constructorFun: sandbox[constructor]
+    }, prefix);
+  }
+
+  if (type.tab && !DebuggerServer.tabActorFactories.hasOwnProperty(prefix)) {
+    DebuggerServer.addTabActor({
+      constructorName: constructor,
+      constructorFun: sandbox[constructor]
+    }, prefix);
+  }
+};
+
+exports.unregisterActor = function (options) {
+  // Unregister in the current process
+  exports.unregisterActorInCurrentProcess(options);
+  // Unregister in any child processes
+  DebuggerServer.setupInChild({
+    module: "devtools/server/actors/utils/actor-registry-utils",
+    setupChild: "unregisterActorInCurrentProcess",
+    args: [options]
+  });
+};
+
+exports.unregisterActorInCurrentProcess = function (options) {
+  if (options.tab) {
+    DebuggerServer.removeTabActor(options);
+  }
+
+  if (options.global) {
+    DebuggerServer.removeGlobalActor(options);
+  }
+};
diff --git a/devtools/server/actors/utils/audionodes.json b/devtools/server/actors/utils/audionodes.json
new file mode 100644
index 000000000..12cc6c34b
--- /dev/null
+++ b/devtools/server/actors/utils/audionodes.json
@@ -0,0 +1,113 @@
+{
+  "OscillatorNode": {
+    "source": true,
+    "properties": {
+      "type": {},
+      "frequency": {
+        "param": true
+      },
+      "detune": {
+        "param": true
+      }
+    }
+  },
+  "GainNode": {
+    "properties": { "gain": { "param": true }}
+  },
+  "DelayNode": {
+    "properties": { "delayTime": { "param": true }}
+  },
+  "AudioBufferSourceNode": {
+    "source": true,
+    "properties": {
+      "buffer": { "Buffer": true },
+      "playbackRate": {
+        "param": true
+      },
+      "loop": {},
+      "loopStart": {},
+      "loopEnd": {}
+    }
+  },
+  "ScriptProcessorNode": {
+    "properties": { "bufferSize": { "readonly": true }}
+  },
+  "PannerNode": {
+    "properties": {
+      "panningModel": {},
+      "distanceModel": {},
+      "refDistance": {},
+      "maxDistance": {},
+      "rolloffFactor": {},
+      "coneInnerAngle": {},
+      "coneOuterAngle": {},
+      "coneOuterGain": {}
+    }
+  },
+  "ConvolverNode": {
+    "properties": {
+      "buffer": { "Buffer": true },
+      "normalize": {}
+    }
+  },
+  "DynamicsCompressorNode": {
+    "properties": {
+      "threshold": { "param": true },
+      "knee": { "param": true },
+      "ratio": { "param": true },
+      "reduction": {},
+      "attack": { "param": true },
+      "release": { "param": true }
+    }
+  },
+  "BiquadFilterNode": {
+    "properties": {
+      "type": {},
+      "frequency": { "param": true },
+      "Q": { "param": true },
+      "detune": { "param": true },
+      "gain": { "param": true }
+    }
+  },
+  "WaveShaperNode": {
+    "properties": {
+      "curve": { "Float32Array": true },
+      "oversample": {}
+    }
+  },
+  "AnalyserNode": {
+    "properties": {
+      "fftSize": {},
+      "minDecibels": {},
+      "maxDecibels": {},
+      "smoothingTimeConstant": {},
+      "frequencyBinCount": { "readonly": true }
+    }
+  },
+  "AudioDestinationNode": {
+    "unbypassable": true
+  },
+  "ChannelSplitterNode": {
+    "unbypassable": true
+  },
+  "ChannelMergerNode": {
+    "unbypassable": true
+  },
+  "MediaElementAudioSourceNode": {
+    "source": true
+  },
+  "MediaStreamAudioSourceNode": {
+    "source": true
+  },
+  "MediaStreamAudioDestinationNode": {
+    "unbypassable": true,
+    "properties": {
+      "stream": { "MediaStream": true }
+    }
+  },
+  "StereoPannerNode": {
+    "properties": {
+      "pan": { "param": true }
+    }
+  }
+}
diff --git a/devtools/server/actors/utils/automation-timeline.js b/devtools/server/actors/utils/automation-timeline.js
new file mode 100644
index 000000000..a086d90be
--- /dev/null
+++ b/devtools/server/actors/utils/automation-timeline.js
@@ -0,0 +1,373 @@
+/**
+ * web-audio-automation-timeline - 1.0.3
+ * https://github.com/jsantell/web-audio-automation-timeline
+ * MIT License, copyright (c) 2014 Jordan Santell
+ */
+!function(e){if("object"==typeof exports&&"undefined"!=typeof module)module.exports=e();else if("function"==typeof define&&define.amd)define([],e);else{var f;"undefined"!=typeof window?f=window:"undefined"!=typeof global?f=global:"undefined"!=typeof self&&(f=self),f.Timeline=e()}}(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
+module.exports = require("./lib/timeline").Timeline;
+
+},{"./lib/timeline":4}],2:[function(require,module,exports){
+var F = require("./formulas");
+
+function TimelineEvent (eventName, value, time, timeConstant, duration) {
+  this.type = eventName;
+  this.value = value;
+  this.time = time;
+  this.constant = timeConstant || 0;
+  this.duration = duration || 0;
+}
+exports.TimelineEvent = TimelineEvent;
+
+
+TimelineEvent.prototype.exponentialApproach = function (lastValue, time) {
+  return F.exponentialApproach(this.time, lastValue, this.value, this.constant, time);
+}
+
+TimelineEvent.prototype.extractValueFromCurve = function (time) {
+  return F.extractValueFromCurve(this.time, this.value, this.value.length, this.duration, time);
+}
+
+TimelineEvent.prototype.linearInterpolate = function (next, time) {
+  return F.linearInterpolate(this.time, this.value, next.time, next.value, time);
+}
+
+TimelineEvent.prototype.exponentialInterpolate = function (next, time) {
+  return F.exponentialInterpolate(this.time, this.value, next.time, next.value, time);
+}
+
+},{"./formulas":3}],3:[function(require,module,exports){
+var EPSILON = 0.0000000001;
+
+exports.linearInterpolate = function (t0, v0, t1, v1, t) {
+  return v0 + (v1 - v0) * ((t - t0) / (t1 - t0));
+};
+
+exports.exponentialInterpolate = function (t0, v0, t1, v1, t) {
+  return v0 * Math.pow(v1 / v0, (t - t0) / (t1 - t0));
+};
+
+exports.extractValueFromCurve = function (start, curve, curveLength, duration, t) {
+  var ratio;
+
+  // If time is after duration, return the last curve value,
+  // or if ratio is >= 1
+  if (t >= start + duration || (ratio = Math.max((t - start) / duration, 0)) >= 1) {
+    return curve[curveLength - 1];
+  }
+
+  return curve[~~(curveLength * ratio)];
+};
+
+exports.exponentialApproach = function (t0, v0, v1, timeConstant, t) {
+  return v1 + (v0 - v1) * Math.exp(-(t - t0) / timeConstant);
+};
+
+// Since we are going to accumulate error by adding 0.01 multiple times
+// in a loop, we want to fuzz the equality check in `getValueAtTime`
+exports.fuzzyEqual = function (lhs, rhs) {
+  return Math.abs(lhs - rhs) < EPSILON;
+};
+
+exports.EPSILON = EPSILON;
+
+},{}],4:[function(require,module,exports){
+var TimelineEvent = require("./event").TimelineEvent;
+var F = require("./formulas");
+
+exports.Timeline = Timeline;
+
+function Timeline (defaultValue) {
+  this.events = [];
+
+  this._value = defaultValue || 0;
+}
+
+Timeline.prototype.getEventCount = function () {
+  return this.events.length;
+};
+
+Timeline.prototype.value = function () {
+  return this._value;
+};
+
+Timeline.prototype.setValue = function (value) {
+  if (this.events.length === 0) {
+    this._value = value;
+  }
+};
+
+Timeline.prototype.getValue = function () {
+  if (this.events.length) {
+    throw new Error("Can only call `getValue` when there are 0 events.");
+  }
+
+  return this._value;
+};
+
+Timeline.prototype.getValueAtTime = function (time) {
+  return this._getValueAtTimeHelper(time);
+};
+
+Timeline.prototype._getValueAtTimeHelper = function (time) {
+  var bailOut = false;
+  var previous = null;
+  var next = null;
+  var lastComputedValue = null; // Used for `setTargetAtTime` nodes
+  var events = this.events;
+  var e;
+
+  for (var i = 0; !bailOut && i < events.length; i++) {
+    if (F.fuzzyEqual(time, events[i].time)) {
+      // Find the last event with the same time as `time`
+      do {
+        ++i;
+      } while (i < events.length && F.fuzzyEqual(time, events[i].time));
+
+      e = events[i - 1];
+
+      // `setTargetAtTime` can be handled no matter what their next event is (if they have one)
+      if (e.type === "setTargetAtTime") {
+        lastComputedValue = this._lastComputedValue(e);
+        return e.exponentialApproach(lastComputedValue, time);
+      }
+
+      // `setValueCurveAtTime` events can be handled no matter what their next event node is
+      // (if they have one)
+      if (e.type === "setValueCurveAtTime") {
+        return e.extractValueFromCurve(time);
+      }
+
+      // For other event types
+      return e.value;
+    }
+    previous = next;
+    next = events[i];
+
+    if (time < events[i].time) {
+      bailOut = true;
+    }
+  }
+
+  // Handle the case where the time is past all of the events
+  if (!bailOut) {
+    previous = next;
+    next = null;
+  }
+
+  // Just return the default value if we did not find anything
+  if (!previous && !next) {
+    return this._value;
+  }
+
+  // If the requested time is before all of the existing events
+  if (!previous) {
+    return this._value;
+  }
+
+  // `setTargetAtTime` can be handled no matter what their next event is (if they have one)
+  if (previous.type === "setTargetAtTime") {
+    lastComputedValue = this._lastComputedValue(previous);
+    return previous.exponentialApproach(lastComputedValue, time);
+  }
+
+  // `setValueCurveAtTime` events can be handled no matter what their next event node is
+  // (if they have one)
+  if (previous.type === "setValueCurveAtTime") {
+    return previous.extractValueFromCurve(time);
+  }
+
+  if (!next) {
+    if (~["setValueAtTime", "linearRampToValueAtTime", "exponentialRampToValueAtTime"].indexOf(previous.type)) {
+      return previous.value;
+    }
+    if (previous.type === "setValueCurveAtTime") {
+      return previous.extractValueFromCurve(time);
+    }
+    if (previous.type === "setTargetAtTime") {
+      throw new Error("unreached");
+    }
+    throw new Error("unreached");
+  }
+
+  // Finally handle the case where we have both a previous and a next event
+  // First handle the case where our range ends up in a ramp event
+  if (next.type === "linearRampToValueAtTime") {
+    return previous.linearInterpolate(next, time);
+  } else if (next.type === "exponentialRampToValueAtTime") {
+    return previous.exponentialInterpolate(next, time);
+  }
+
+  // Now handle all other cases
+  if (~["setValueAtTime", "linearRampToValueAtTime", "exponentialRampToValueAtTime"].indexOf(previous.type)) {
+    // If the next event type is neither linear or exponential ramp,
+    // the value is constant.
+    return previous.value;
+  }
+  if (previous.type === "setValueCurveAtTime") {
+    return previous.extractValueFromCurve(time);
+  }
+  if (previous.type === "setTargetAtTime") {
+    throw new Error("unreached");
+  }
+  throw new Error("unreached");
+};
+
+Timeline.prototype._insertEvent = function (ev) {
+  var events = this.events;
+
+  if (ev.type === "setValueCurveAtTime") {
+    if (!ev.value || !ev.value.length) {
+      throw new Error("NS_ERROR_DOM_SYNTAX_ERR");
+    }
+  }
+
+  if (ev.type === "setTargetAtTime") {
+    if (F.fuzzyEqual(ev.constant, 0)) {
+      throw new Error("NS_ERROR_DOM_SYNTAX_ERR");
+    }
+  }
+
+  // Make sure that non-curve events don't fall within the duration of a
+  // curve event.
+  for (var i = 0; i < events.length; i++) {
+    if (events[i].type === "setValueCurveAtTime" &&
+        events[i].time <= ev.time &&
+        (events[i].time + events[i].duration) >= ev.time) {
+      throw new Error("NS_ERROR_DOM_SYNTAX_ERR");
+    }
+  }
+
+  // Make sure that curve events don't fall in a range which includes other
+  // events.
+  if (ev.type === "setValueCurveAtTime") {
+    for (var i = 0; i < events.length; i++) {
+      if (events[i].time > ev.time &&
+          events[i].time < (ev.time + ev.duration)) {
+        throw new Error("NS_ERROR_DOM_SYNTAX_ERR");
+      }
+    }
+  }
+
+  // Make sure that invalid values are not used for exponential curves
+  if (ev.type === "exponentialRampToValueAtTime") {
+    if (ev.value <= 0) throw new Error("NS_ERROR_DOM_SYNTAX_ERR");
+    var prev = this._getPreviousEvent(ev.time);
+    if (prev) {
+      if (prev.value <= 0) {
+        throw new Error("NS_ERROR_DOM_SYNTAX_ERR");
+      }
+    } else {
+      if (this._value <= 0) {
+        throw new Error("NS_ERROR_DOM_SYNTAX_ERR");
+      }
+    }
+  }
+
+  for (var i = 0; i < events.length; i++) {
+    if (ev.time === events[i].time) {
+      if (ev.type === events[i].type) {
+        // If times and types are equal, replace the event;
+        events[i] = ev;
+      } else {
+        // Otherwise, place the element after the last event of another type
+        do { i++; }
+        while (i < events.length && ev.type !== events[i].type && ev.time === events[i].time);
+        events.splice(i, 0, ev);
+      }
+      return;
+    }
+    // Otherwise, place the event right after the latest existing event
+    if (ev.time < events[i].time) {
+      events.splice(i, 0, ev);
+      return;
+    }
+  }
+
+  // If we couldn't find a place for the event, just append it to the list
+  this.events.push(ev);
+};
+
+Timeline.prototype._getPreviousEvent = function (time) {
+  var previous = null, next = null;
+  var bailOut = false;
+  var events = this.events;
+
+  for (var i = 0; !bailOut && i < events.length; i++) {
+    if (time === events[i]) {
+      do { ++i; }
+      while (i < events.length && time === events[i].time);
+      return events[i - 1];
+    }
+    previous = next;
+    next = events[i];
+    if (time < events[i].time) {
+      bailOut = true;
+    }
+  }
+
+  // Handle the case where the time is past all the events
+  if (!bailOut) {
+    previous = next;
+  }
+
+  return previous;
+};
+
+/**
+ * Calculates the previous value of the timeline, used for
+ * `setTargetAtTime` nodes. Takes an event, and returns
+ * the previous computed value for any sample taken during that
+ * exponential approach node.
+ */
+Timeline.prototype._lastComputedValue = function (event) {
+  // If equal times, return the value for the previous event, before
+  // the `setTargetAtTime` node.
+  var lastEvent = this._getPreviousEvent(event.time - F.EPSILON);
+
+  // If no event before the setTargetAtTime event, then return the
+  // intrinsic value.
+  if (!lastEvent) {
+    return this._value;
+  }
+  // Otherwise, return the value for the previous event, which should
+  // always be the last computed value (? I think?)
+  else {
+    return lastEvent.value;
+  }
+};
+
+Timeline.prototype.setValueAtTime = function (value, startTime) {
+  this._insertEvent(new TimelineEvent("setValueAtTime", value, startTime));
+};
+
+Timeline.prototype.linearRampToValueAtTime = function (value, endTime) {
+  this._insertEvent(new TimelineEvent("linearRampToValueAtTime", value, endTime));
+};
+
+Timeline.prototype.exponentialRampToValueAtTime = function (value, endTime) {
+  this._insertEvent(new TimelineEvent("exponentialRampToValueAtTime", value, endTime));
+};
+
+Timeline.prototype.setTargetAtTime = function (value, startTime, timeConstant) {
+  this._insertEvent(new TimelineEvent("setTargetAtTime", value, startTime, timeConstant));
+};
+
+Timeline.prototype.setValueCurveAtTime = function (value, startTime, duration) {
+  this._insertEvent(new TimelineEvent("setValueCurveAtTime", value, startTime, null, duration));
+};
+
+Timeline.prototype.cancelScheduledValues = function (time) {
+  for (var i = 0; i < this.events.length; i++) {
+    if (this.events[i].time >= time) {
+      this.events = this.events.slice(0, i);
+      break;
+    }
+  }
+};
+
+Timeline.prototype.cancelAllEvents = function () {
+  this.events.length = 0;
+};
+
+},{"./event":2,"./formulas":3}]},{},[1])(1)
+});
\ No newline at end of file
diff --git a/devtools/server/actors/utils/css-grid-utils.js b/devtools/server/actors/utils/css-grid-utils.js
new file mode 100644
index 000000000..0b260117d
--- /dev/null
+++ b/devtools/server/actors/utils/css-grid-utils.js
@@ -0,0 +1,61 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Cu } = require("chrome");
+
+/**
+ * Returns the grid fragment array with all the grid fragment data stringifiable.
+ *
+ * @param  {Object} fragments
+ *         Grid fragment object.
+ * @return {Array} representation with the grid fragment data stringifiable.
+ */
+function getStringifiableFragments(fragments = []) {
+  if (fragments[0] && Cu.isDeadWrapper(fragments[0])) {
+    return {};
+  }
+
+  return fragments.map(getStringifiableFragment);
+}
+
+/**
+ * Returns a string representation of the CSS Grid data as returned by
+ * node.getGridFragments. This is useful to compare grid state at each update and redraw
+ * the highlighter if needed. It also seralizes the grid fragment data so it can be used
+ * by protocol.js.
+ *
+ * @param  {Object} fragments
+ *         Grid fragment object.
+ * @return {String} representation of the CSS grid fragment data.
+ */
+function stringifyGridFragments(fragments) {
+  return JSON.stringify(getStringifiableFragments(fragments));
+}
+
+function getStringifiableFragment(fragment) {
+  return {
+    cols: getStringifiableDimension(fragment.cols),
+    rows: getStringifiableDimension(fragment.rows)
+  };
+}
+
+function getStringifiableDimension(dimension) {
+  return {
+    lines: [...dimension.lines].map(getStringifiableLine),
+    tracks: [...dimension.tracks].map(getStringifiableTrack),
+  };
+}
+
+function getStringifiableLine({ breadth, number, start, names }) {
+  return { breadth, number, start, names };
+}
+
+function getStringifiableTrack({ breadth, start, state, type }) {
+  return { breadth, start, state, type };
+}
+
+exports.getStringifiableFragments = getStringifiableFragments;
+exports.stringifyGridFragments = stringifyGridFragments;
diff --git a/devtools/server/actors/utils/make-debugger.js b/devtools/server/actors/utils/make-debugger.js
new file mode 100644
index 000000000..9bd43e567
--- /dev/null
+++ b/devtools/server/actors/utils/make-debugger.js
@@ -0,0 +1,101 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const EventEmitter = require("devtools/shared/event-emitter");
+const Debugger = require("Debugger");
+
+const { reportException } = require("devtools/shared/DevToolsUtils");
+
+/**
+ * Multiple actors that use a |Debugger| instance come in a few versions, each
+ * with a different set of debuggees. One version for content tabs (globals
+ * within a tab), one version for chrome debugging (all globals), and sometimes
+ * a third version for addon debugging (chrome globals the addon is loaded in
+ * and content globals the addon injects scripts into). The |makeDebugger|
+ * function helps us avoid repeating the logic for finding and maintaining the
+ * correct set of globals for a given |Debugger| instance across each version of
+ * all of our actors.
+ *
+ * The |makeDebugger| function expects a single object parameter with the
+ * following properties:
+ *
+ * @param Function findDebuggees
+ *        Called with one argument: a |Debugger| instance. This function should
+ *        return an iterable of globals to be added to the |Debugger|
+ *        instance. The globals may be wrapped in a |Debugger.Object|, or
+ *        unwrapped.
+ *
+ * @param Function shouldAddNewGlobalAsDebuggee
+ *        Called with one argument: a |Debugger.Object| wrapping a global
+ *        object. This function must return |true| if the global object should
+ *        be added as debuggee, and |false| otherwise.
+ *
+ * @returns Debugger
+ *          Returns a |Debugger| instance that can manage its set of debuggee
+ *          globals itself and is decorated with the |EventEmitter| class.
+ *
+ *          Events emitted by the returned |Debugger| instance:
+ *
+ *            - "newGlobal": Emitted when a new global has been added as a
+ *               debuggee. Passes the |Debugger.Object| wrapping the new
+ *               debuggee global to listeners.
+ *
+ *          Existing |Debugger| properties set on the returned |Debugger|
+ *          instance:
+ *
+ *            - onNewGlobalObject: The |Debugger| will automatically add new
+ *              globals as debuggees if calling |shouldAddNewGlobalAsDebuggee|
+ *              with the global returns true.
+ *
+ *            - uncaughtExceptionHook: The |Debugger| already has an error
+ *              reporter attached to |uncaughtExceptionHook|, so if any
+ *              |Debugger| hooks fail, the error will be reported.
+ *
+ *          New properties set on the returned |Debugger| instance:
+ *
+ *            - addDebuggees: A function which takes no arguments. It adds all
+ *              current globals that should be debuggees (as determined by
+ *              |findDebuggees|) to the |Debugger| instance.
+ */
+module.exports = function makeDebugger({ findDebuggees, shouldAddNewGlobalAsDebuggee }) {
+  const dbg = new Debugger();
+  EventEmitter.decorate(dbg);
+
+  dbg.allowUnobservedAsmJS = true;
+  dbg.uncaughtExceptionHook = reportDebuggerHookException;
+
+  dbg.onNewGlobalObject = function (global) {
+    if (shouldAddNewGlobalAsDebuggee(global)) {
+      safeAddDebuggee(this, global);
+    }
+  };
+
+  dbg.addDebuggees = function () {
+    for (let global of findDebuggees(this)) {
+      safeAddDebuggee(this, global);
+    }
+  };
+
+  return dbg;
+};
+
+const reportDebuggerHookException = e => reportException("Debugger Hook", e);
+
+/**
+ * Add |global| as a debuggee to |dbg|, handling error cases.
+ */
+function safeAddDebuggee(dbg, global) {
+  try {
+    let wrappedGlobal = dbg.addDebuggee(global);
+    if (wrappedGlobal) {
+      dbg.emit("newGlobal", wrappedGlobal);
+    }
+  } catch (e) {
+    // Ignoring attempt to add the debugger's compartment as a debuggee.
+  }
+}
diff --git a/devtools/server/actors/utils/map-uri-to-addon-id.js b/devtools/server/actors/utils/map-uri-to-addon-id.js
new file mode 100644
index 000000000..6f3316b14
--- /dev/null
+++ b/devtools/server/actors/utils/map-uri-to-addon-id.js
@@ -0,0 +1,44 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const DevToolsUtils = require("devtools/shared/DevToolsUtils");
+const Services = require("Services");
+
+loader.lazyServiceGetter(this, "AddonPathService",
+                         "@mozilla.org/addon-path-service;1",
+                         "amIAddonPathService");
+
+const B2G_ID = "{3c2e2abc-06d4-11e1-ac3b-374f68613e61}";
+const GRAPHENE_ID = "{d1bfe7d9-c01e-4237-998b-7b5f960a4314}";
+
+/**
+ * This is a wrapper around amIAddonPathService.mapURIToAddonID which always returns
+ * false on B2G and graphene to avoid loading the add-on manager there and
+ * reports any exceptions rather than throwing so that the caller doesn't have
+ * to worry about them.
+ */
+if (!Services.appinfo
+    || Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT
+    || Services.appinfo.ID === undefined /* XPCShell */
+    || Services.appinfo.ID == B2G_ID
+    || Services.appinfo.ID == GRAPHENE_ID
+    || !AddonPathService) {
+  module.exports = function mapURIToAddonId(uri) {
+    return false;
+  };
+} else {
+  module.exports = function mapURIToAddonId(uri) {
+    try {
+      return AddonPathService.mapURIToAddonId(uri);
+    }
+    catch (e) {
+      DevToolsUtils.reportException("mapURIToAddonId", e);
+      return false;
+    }
+  };
+}
diff --git a/devtools/server/actors/utils/moz.build b/devtools/server/actors/utils/moz.build
new file mode 100644
index 000000000..0dcf40faf
--- /dev/null
+++ b/devtools/server/actors/utils/moz.build
@@ -0,0 +1,19 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    'actor-registry-utils.js',
+    'audionodes.json',
+    'automation-timeline.js',
+    'css-grid-utils.js',
+    'make-debugger.js',
+    'map-uri-to-addon-id.js',
+    'stack.js',
+    'TabSources.js',
+    'walker-search.js',
+    'webconsole-utils.js',
+    'webconsole-worker-utils.js',
+)
diff --git a/devtools/server/actors/utils/stack.js b/devtools/server/actors/utils/stack.js
new file mode 100644
index 000000000..a6a3d1137
--- /dev/null
+++ b/devtools/server/actors/utils/stack.js
@@ -0,0 +1,185 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var {Class} = require("sdk/core/heritage");
+
+/**
+ * A helper class that stores stack frame objects.  Each frame is
+ * assigned an index, and if a frame is added more than once, the same
+ * index is used.  Users of the class can get an array of all frames
+ * that have been added.
+ */
+var StackFrameCache = Class({
+  /**
+   * Initialize this object.
+   */
+  initialize: function () {
+    this._framesToIndices = null;
+    this._framesToForms = null;
+    this._lastEventSize = 0;
+  },
+
+  /**
+   * Prepare to accept frames.
+   */
+  initFrames: function () {
+    if (this._framesToIndices) {
+      // The maps are already initialized.
+      return;
+    }
+
+    this._framesToIndices = new Map();
+    this._framesToForms = new Map();
+    this._lastEventSize = 0;
+  },
+
+  /**
+   * Forget all stored frames and reset to the initialized state.
+   */
+  clearFrames: function () {
+    this._framesToIndices.clear();
+    this._framesToIndices = null;
+    this._framesToForms.clear();
+    this._framesToForms = null;
+    this._lastEventSize = 0;
+  },
+
+  /**
+   * Add a frame to this stack frame cache, and return the index of
+   * the frame.
+   */
+  addFrame: function (frame) {
+    this._assignFrameIndices(frame);
+    this._createFrameForms(frame);
+    return this._framesToIndices.get(frame);
+  },
+
+  /**
+   * A helper method for the memory actor.  This populates the packet
+   * object with "frames" property. Each of these
+   * properties will be an array indexed by frame ID.  "frames" will
+   * contain frame objects (see makeEvent).
+   *
+   * @param packet
+   *        The packet to update.
+   *
+   * @returns packet
+   */
+  updateFramePacket: function (packet) {
+    // Now that we are guaranteed to have a form for every frame, we know the
+    // size the "frames" property's array must be. We use that information to
+    // create dense arrays even though we populate them out of order.
+    const size = this._framesToForms.size;
+    packet.frames = Array(size).fill(null);
+
+    // Populate the "frames" properties.
+    for (let [stack, index] of this._framesToIndices) {
+      packet.frames[index] = this._framesToForms.get(stack);
+    }
+
+    return packet;
+  },
+
+  /**
+   * If any new stack frames have been added to this cache since the
+   * last call to makeEvent (clearing the cache also resets the "last
+   * call"), then return a new array describing the new frames.  If no
+   * new frames are available, return null.
+   *
+   * The frame cache assumes that the user of the cache keeps track of
+   * all previously-returned arrays and, in theory, concatenates them
+   * all to form a single array holding all frames added to the cache
+   * since the last reset.  This concatenated array can be indexed by
+   * the frame ID.  The array returned by this function, though, is
+   * dense and starts at 0.
+   *
+   * Each element in the array is an object of the form:
+   * {
+   *   line: <line number for this frame>,
+   *   column: <column number for this frame>,
+   *   source: <filename string for this frame>,
+   *   functionDisplayName: <this frame's inferred function name function or null>,
+   *   parent: <frame ID -- an index into the concatenated array mentioned above>
+   *   asyncCause: the async cause, or null
+   *   asyncParent: <frame ID -- an index into the concatenated array mentioned above>
+   * }
+   *
+   * The intent of this approach is to make it simpler to efficiently
+   * send frame information over the debugging protocol, by only
+   * sending new frames.
+   *
+   * @returns array or null
+   */
+  makeEvent: function () {
+    const size = this._framesToForms.size;
+    if (!size || size <= this._lastEventSize) {
+      return null;
+    }
+
+    let packet = Array(size - this._lastEventSize).fill(null);
+    for (let [stack, index] of this._framesToIndices) {
+      if (index >= this._lastEventSize) {
+        packet[index - this._lastEventSize] = this._framesToForms.get(stack);
+      }
+    }
+
+    this._lastEventSize = size;
+
+    return packet;
+  },
+
+  /**
+   * Assigns an index to the given frame and its parents, if an index is not
+   * already assigned.
+   *
+   * @param SavedFrame frame
+   *        A frame to assign an index to.
+   */
+  _assignFrameIndices: function (frame) {
+    if (this._framesToIndices.has(frame)) {
+      return;
+    }
+
+    if (frame) {
+      this._assignFrameIndices(frame.parent);
+      this._assignFrameIndices(frame.asyncParent);
+    }
+
+    const index = this._framesToIndices.size;
+    this._framesToIndices.set(frame, index);
+  },
+
+  /**
+   * Create the form for the given frame, if one doesn't already exist.
+   *
+   * @param SavedFrame frame
+   *        A frame to create a form for.
+   */
+  _createFrameForms: function (frame) {
+    if (this._framesToForms.has(frame)) {
+      return;
+    }
+
+    let form = null;
+    if (frame) {
+      form = {
+        line: frame.line,
+        column: frame.column,
+        source: frame.source,
+        functionDisplayName: frame.functionDisplayName,
+        parent: this._framesToIndices.get(frame.parent),
+        asyncParent: this._framesToIndices.get(frame.asyncParent),
+        asyncCause: frame.asyncCause
+      };
+      this._createFrameForms(frame.parent);
+      this._createFrameForms(frame.asyncParent);
+    }
+
+    this._framesToForms.set(frame, form);
+  },
+});
+
+exports.StackFrameCache = StackFrameCache;
diff --git a/devtools/server/actors/utils/walker-search.js b/devtools/server/actors/utils/walker-search.js
new file mode 100644
index 000000000..0955a3919
--- /dev/null
+++ b/devtools/server/actors/utils/walker-search.js
@@ -0,0 +1,278 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * The walker-search module provides a simple API to index and search strings
+ * and elements inside a given document.
+ * It indexes tag names, attribute names and values, and text contents.
+ * It provides a simple search function that returns a list of nodes that
+ * matched.
+ */
+
+const {Ci, Cu} = require("chrome");
+
+/**
+ * The WalkerIndex class indexes the document (and all subdocs) from
+ * a given walker.
+ *
+ * It is only indexed the first time the data is accessed and will be
+ * re-indexed if a mutation happens between requests.
+ *
+ * @param {Walker} walker The walker to be indexed
+ */
+function WalkerIndex(walker) {
+  this.walker = walker;
+  this.clearIndex = this.clearIndex.bind(this);
+
+  // Kill the index when mutations occur, the next data get will re-index.
+  this.walker.on("any-mutation", this.clearIndex);
+}
+
+WalkerIndex.prototype = {
+  /**
+   * Destroy this instance, releasing all data and references
+   */
+  destroy: function () {
+    this.walker.off("any-mutation", this.clearIndex);
+  },
+
+  clearIndex: function () {
+    if (!this.currentlyIndexing) {
+      this._data = null;
+    }
+  },
+
+  get doc() {
+    return this.walker.rootDoc;
+  },
+
+  /**
+   * Get the indexed data
+   * This getter also indexes if it hasn't been done yet or if the state is
+   * dirty
+   *
+   * @returns Map<String, Array<{type:String, node:DOMNode}>>
+   *          A Map keyed on the searchable value, containing an array with
+   *          objects containing the 'type' (one of ALL_RESULTS_TYPES), and
+   *          the DOM Node.
+   */
+  get data() {
+    if (!this._data) {
+      this._data = new Map();
+      this.index();
+    }
+
+    return this._data;
+  },
+
+  _addToIndex: function (type, node, value) {
+    // Add an entry for this value if there isn't one
+    let entry = this._data.get(value);
+    if (!entry) {
+      this._data.set(value, []);
+    }
+
+    // Add the type/node to the list
+    this._data.get(value).push({
+      type: type,
+      node: node
+    });
+  },
+
+  index: function () {
+    // Handle case where iterating nextNode() with the deepTreeWalker triggers
+    // a mutation (Bug 1222558)
+    this.currentlyIndexing = true;
+
+    let documentWalker = this.walker.getDocumentWalker(this.doc);
+    while (documentWalker.nextNode()) {
+      let node = documentWalker.currentNode;
+
+      if (node.nodeType === 1) {
+        // For each element node, we get the tagname and all attributes names
+        // and values
+        let localName = node.localName;
+        if (localName === "_moz_generated_content_before") {
+          this._addToIndex("tag", node, "::before");
+          this._addToIndex("text", node, node.textContent.trim());
+        } else if (localName === "_moz_generated_content_after") {
+          this._addToIndex("tag", node, "::after");
+          this._addToIndex("text", node, node.textContent.trim());
+        } else {
+          this._addToIndex("tag", node, node.localName);
+        }
+
+        for (let {name, value} of node.attributes) {
+          this._addToIndex("attributeName", node, name);
+          this._addToIndex("attributeValue", node, value);
+        }
+      } else if (node.textContent && node.textContent.trim().length) {
+        // For comments and text nodes, we get the text
+        this._addToIndex("text", node, node.textContent.trim());
+      }
+    }
+
+    this.currentlyIndexing = false;
+  }
+};
+
+exports.WalkerIndex = WalkerIndex;
+
+/**
+ * The WalkerSearch class provides a way to search an indexed document as well
+ * as find elements that match a given css selector.
+ *
+ * Usage example:
+ * let s = new WalkerSearch(doc);
+ * let res = s.search("lang", index);
+ * for (let {matched, results} of res) {
+ *   for (let {node, type} of results) {
+ *     console.log("The query matched a node's " + type);
+ *     console.log("Node that matched", node);
+ *    }
+ * }
+ * s.destroy();
+ *
+ * @param {Walker} the walker to be searched
+ */
+function WalkerSearch(walker) {
+  this.walker = walker;
+  this.index = new WalkerIndex(this.walker);
+}
+
+WalkerSearch.prototype = {
+  destroy: function () {
+    this.index.destroy();
+    this.walker = null;
+  },
+
+  _addResult: function (node, type, results) {
+    if (!results.has(node)) {
+      results.set(node, []);
+    }
+
+    let matches = results.get(node);
+
+    // Do not add if the exact same result is already in the list
+    let isKnown = false;
+    for (let match of matches) {
+      if (match.type === type) {
+        isKnown = true;
+        break;
+      }
+    }
+
+    if (!isKnown) {
+      matches.push({type});
+    }
+  },
+
+  _searchIndex: function (query, options, results) {
+    for (let [matched, res] of this.index.data) {
+      if (!options.searchMethod(query, matched)) {
+        continue;
+      }
+
+      // Add any relevant results (skipping non-requested options).
+      res.filter(entry => {
+        return options.types.indexOf(entry.type) !== -1;
+      }).forEach(({node, type}) => {
+        this._addResult(node, type, results);
+      });
+    }
+  },
+
+  _searchSelectors: function (query, options, results) {
+    // If the query is just one "word", no need to search because _searchIndex
+    // will lead the same results since it has access to tagnames anyway
+    let isSelector = query && query.match(/[ >~.#\[\]]/);
+    if (options.types.indexOf("selector") === -1 || !isSelector) {
+      return;
+    }
+
+    let nodes = this.walker._multiFrameQuerySelectorAll(query);
+    for (let node of nodes) {
+      this._addResult(node, "selector", results);
+    }
+  },
+
+  /**
+   * Search the document
+   * @param {String} query What to search for
+   * @param {Object} options The following options are accepted:
+   * - searchMethod {String} one of WalkerSearch.SEARCH_METHOD_*
+   *   defaults to WalkerSearch.SEARCH_METHOD_CONTAINS (does not apply to
+   *   selector search type)
+   * - types {Array} a list of things to search for (tag, text, attributes, etc)
+   *   defaults to WalkerSearch.ALL_RESULTS_TYPES
+   * @return {Array} An array is returned with each item being an object like:
+   * {
+   *   node: <the dom node that matched>,
+   *   type: <the type of match: one of WalkerSearch.ALL_RESULTS_TYPES>
+   * }
+   */
+  search: function (query, options = {}) {
+    options.searchMethod = options.searchMethod || WalkerSearch.SEARCH_METHOD_CONTAINS;
+    options.types = options.types || WalkerSearch.ALL_RESULTS_TYPES;
+
+    // Empty strings will return no results, as will non-string input
+    if (typeof query !== "string") {
+      query = "";
+    }
+
+    // Store results in a map indexed by nodes to avoid duplicate results
+    let results = new Map();
+
+    // Search through the indexed data
+    this._searchIndex(query, options, results);
+
+    // Search with querySelectorAll
+    this._searchSelectors(query, options, results);
+
+    // Concatenate all results into an Array to return
+    let resultList = [];
+    for (let [node, matches] of results) {
+      for (let {type} of matches) {
+        resultList.push({
+          node: node,
+          type: type,
+        });
+
+        // For now, just do one result per node since the frontend
+        // doesn't have a way to highlight each result individually
+        // yet.
+        break;
+      }
+    }
+
+    let documents = this.walker.tabActor.windows.map(win=>win.document);
+
+    // Sort the resulting nodes by order of appearance in the DOM
+    resultList.sort((a, b) => {
+      // Disconnected nodes won't get good results from compareDocumentPosition
+      // so check the order of their document instead.
+      if (a.node.ownerDocument != b.node.ownerDocument) {
+        let indA = documents.indexOf(a.node.ownerDocument);
+        let indB = documents.indexOf(b.node.ownerDocument);
+        return indA - indB;
+      }
+      // If the same document, then sort on DOCUMENT_POSITION_FOLLOWING (4)
+      // which means B is after A.
+      return a.node.compareDocumentPosition(b.node) & 4 ? -1 : 1;
+    });
+
+    return resultList;
+  }
+};
+
+WalkerSearch.SEARCH_METHOD_CONTAINS = (query, candidate) => {
+  return query && candidate.toLowerCase().indexOf(query.toLowerCase()) !== -1;
+};
+
+WalkerSearch.ALL_RESULTS_TYPES = ["tag", "text", "attributeName",
+                                  "attributeValue", "selector"];
+
+exports.WalkerSearch = WalkerSearch;
diff --git a/devtools/server/actors/utils/webconsole-utils.js b/devtools/server/actors/utils/webconsole-utils.js
new file mode 100644
index 000000000..597f1ddb3
--- /dev/null
+++ b/devtools/server/actors/utils/webconsole-utils.js
@@ -0,0 +1,1063 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft= javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {Cc, Ci, Cu, components} = require("chrome");
+const {isWindowIncluded} = require("devtools/shared/layout/utils");
+const Services = require("Services");
+const {XPCOMUtils} = require("resource://gre/modules/XPCOMUtils.jsm");
+
+// TODO: Bug 842672 - browser/ imports modules from toolkit/.
+// Note that these are only used in WebConsoleCommands, see $0 and pprint().
+loader.lazyImporter(this, "VariablesView", "resource://devtools/client/shared/widgets/VariablesView.jsm");
+
+XPCOMUtils.defineLazyServiceGetter(this,
+                                   "swm",
+                                   "@mozilla.org/serviceworkers/manager;1",
+                                   "nsIServiceWorkerManager");
+
+const CONSOLE_WORKER_IDS = exports.CONSOLE_WORKER_IDS = [
+  "SharedWorker",
+  "ServiceWorker",
+  "Worker"
+];
+
+var WebConsoleUtils = {
+
+  /**
+   * Given a message, return one of CONSOLE_WORKER_IDS if it matches
+   * one of those.
+   *
+   * @return string
+   */
+  getWorkerType: function (message) {
+    let id = message ? message.innerID : null;
+    return CONSOLE_WORKER_IDS[CONSOLE_WORKER_IDS.indexOf(id)] || null;
+  },
+
+  /**
+   * Clone an object.
+   *
+   * @param object object
+   *        The object you want cloned.
+   * @param boolean recursive
+   *        Tells if you want to dig deeper into the object, to clone
+   *        recursively.
+   * @param function [filter]
+   *        Optional, filter function, called for every property. Three
+   *        arguments are passed: key, value and object. Return true if the
+   *        property should be added to the cloned object. Return false to skip
+   *        the property.
+   * @return object
+   *         The cloned object.
+   */
+  cloneObject: function (object, recursive, filter) {
+    if (typeof object != "object") {
+      return object;
+    }
+
+    let temp;
+
+    if (Array.isArray(object)) {
+      temp = [];
+      Array.forEach(object, function (value, index) {
+        if (!filter || filter(index, value, object)) {
+          temp.push(recursive ? WebConsoleUtils.cloneObject(value) : value);
+        }
+      });
+    } else {
+      temp = {};
+      for (let key in object) {
+        let value = object[key];
+        if (object.hasOwnProperty(key) &&
+            (!filter || filter(key, value, object))) {
+          temp[key] = recursive ? WebConsoleUtils.cloneObject(value) : value;
+        }
+      }
+    }
+
+    return temp;
+  },
+
+  /**
+   * Gets the ID of the inner window of this DOM window.
+   *
+   * @param nsIDOMWindow window
+   * @return integer
+   *         Inner ID for the given window.
+   */
+  getInnerWindowId: function (window) {
+    return window.QueryInterface(Ci.nsIInterfaceRequestor)
+             .getInterface(Ci.nsIDOMWindowUtils).currentInnerWindowID;
+  },
+
+  /**
+   * Recursively gather a list of inner window ids given a
+   * top level window.
+   *
+   * @param nsIDOMWindow window
+   * @return Array
+   *         list of inner window ids.
+   */
+  getInnerWindowIDsForFrames: function (window) {
+    let innerWindowID = this.getInnerWindowId(window);
+    let ids = [innerWindowID];
+
+    if (window.frames) {
+      for (let i = 0; i < window.frames.length; i++) {
+        let frame = window.frames[i];
+        ids = ids.concat(this.getInnerWindowIDsForFrames(frame));
+      }
+    }
+
+    return ids;
+  },
+
+  /**
+   * Get the property descriptor for the given object.
+   *
+   * @param object object
+   *        The object that contains the property.
+   * @param string prop
+   *        The property you want to get the descriptor for.
+   * @return object
+   *         Property descriptor.
+   */
+  getPropertyDescriptor: function (object, prop) {
+    let desc = null;
+    while (object) {
+      try {
+        if ((desc = Object.getOwnPropertyDescriptor(object, prop))) {
+          break;
+        }
+      } catch (ex) {
+        // Native getters throw here. See bug 520882.
+        // null throws TypeError.
+        if (ex.name != "NS_ERROR_XPC_BAD_CONVERT_JS" &&
+            ex.name != "NS_ERROR_XPC_BAD_OP_ON_WN_PROTO" &&
+            ex.name != "TypeError") {
+          throw ex;
+        }
+      }
+
+      try {
+        object = Object.getPrototypeOf(object);
+      } catch (ex) {
+        if (ex.name == "TypeError") {
+          return desc;
+        }
+        throw ex;
+      }
+    }
+    return desc;
+  },
+
+  /**
+   * Create a grip for the given value. If the value is an object,
+   * an object wrapper will be created.
+   *
+   * @param mixed value
+   *        The value you want to create a grip for, before sending it to the
+   *        client.
+   * @param function objectWrapper
+   *        If the value is an object then the objectWrapper function is
+   *        invoked to give us an object grip. See this.getObjectGrip().
+   * @return mixed
+   *         The value grip.
+   */
+  createValueGrip: function (value, objectWrapper) {
+    switch (typeof value) {
+      case "boolean":
+        return value;
+      case "string":
+        return objectWrapper(value);
+      case "number":
+        if (value === Infinity) {
+          return { type: "Infinity" };
+        } else if (value === -Infinity) {
+          return { type: "-Infinity" };
+        } else if (Number.isNaN(value)) {
+          return { type: "NaN" };
+        } else if (!value && 1 / value === -Infinity) {
+          return { type: "-0" };
+        }
+        return value;
+      case "undefined":
+        return { type: "undefined" };
+      case "object":
+        if (value === null) {
+          return { type: "null" };
+        }
+        // Fall through.
+      case "function":
+        return objectWrapper(value);
+      default:
+        console.error("Failed to provide a grip for value of " + typeof value
+                      + ": " + value);
+        return null;
+    }
+  },
+};
+
+exports.Utils = WebConsoleUtils;
+
+// The page errors listener
+
+/**
+ * The nsIConsoleService listener. This is used to send all of the console
+ * messages (JavaScript, CSS and more) to the remote Web Console instance.
+ *
+ * @constructor
+ * @param nsIDOMWindow [window]
+ *        Optional - the window object for which we are created. This is used
+ *        for filtering out messages that belong to other windows.
+ * @param object listener
+ *        The listener object must have one method:
+ *        - onConsoleServiceMessage(). This method is invoked with one argument,
+ *        the nsIConsoleMessage, whenever a relevant message is received.
+ */
+function ConsoleServiceListener(window, listener) {
+  this.window = window;
+  this.listener = listener;
+}
+exports.ConsoleServiceListener = ConsoleServiceListener;
+
+ConsoleServiceListener.prototype =
+{
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIConsoleListener]),
+
+  /**
+   * The content window for which we listen to page errors.
+   * @type nsIDOMWindow
+   */
+  window: null,
+
+  /**
+   * The listener object which is notified of messages from the console service.
+   * @type object
+   */
+  listener: null,
+
+  /**
+   * Initialize the nsIConsoleService listener.
+   */
+  init: function () {
+    Services.console.registerListener(this);
+  },
+
+  /**
+   * The nsIConsoleService observer. This method takes all the script error
+   * messages belonging to the current window and sends them to the remote Web
+   * Console instance.
+   *
+   * @param nsIConsoleMessage message
+   *        The message object coming from the nsIConsoleService.
+   */
+  observe: function (message) {
+    if (!this.listener) {
+      return;
+    }
+
+    if (this.window) {
+      if (!(message instanceof Ci.nsIScriptError) ||
+          !message.outerWindowID ||
+          !this.isCategoryAllowed(message.category)) {
+        return;
+      }
+
+      let errorWindow = Services.wm.getOuterWindowWithId(message.outerWindowID);
+      if (!errorWindow || !isWindowIncluded(this.window, errorWindow)) {
+        return;
+      }
+    }
+
+    this.listener.onConsoleServiceMessage(message);
+  },
+
+  /**
+   * Check if the given message category is allowed to be tracked or not.
+   * We ignore chrome-originating errors as we only care about content.
+   *
+   * @param string category
+   *        The message category you want to check.
+   * @return boolean
+   *         True if the category is allowed to be logged, false otherwise.
+   */
+  isCategoryAllowed: function (category) {
+    if (!category) {
+      return false;
+    }
+
+    switch (category) {
+      case "XPConnect JavaScript":
+      case "component javascript":
+      case "chrome javascript":
+      case "chrome registration":
+      case "XBL":
+      case "XBL Prototype Handler":
+      case "XBL Content Sink":
+      case "xbl javascript":
+        return false;
+    }
+
+    return true;
+  },
+
+  /**
+   * Get the cached page errors for the current inner window and its (i)frames.
+   *
+   * @param boolean [includePrivate=false]
+   *        Tells if you want to also retrieve messages coming from private
+   *        windows. Defaults to false.
+   * @return array
+   *         The array of cached messages. Each element is an nsIScriptError or
+   *         an nsIConsoleMessage
+   */
+  getCachedMessages: function (includePrivate = false) {
+    let errors = Services.console.getMessageArray() || [];
+
+    // if !this.window, we're in a browser console. Still need to filter
+    // private messages.
+    if (!this.window) {
+      return errors.filter((error) => {
+        if (error instanceof Ci.nsIScriptError) {
+          if (!includePrivate && error.isFromPrivateWindow) {
+            return false;
+          }
+        }
+
+        return true;
+      });
+    }
+
+    let ids = WebConsoleUtils.getInnerWindowIDsForFrames(this.window);
+
+    return errors.filter((error) => {
+      if (error instanceof Ci.nsIScriptError) {
+        if (!includePrivate && error.isFromPrivateWindow) {
+          return false;
+        }
+        if (ids &&
+            (ids.indexOf(error.innerWindowID) == -1 ||
+             !this.isCategoryAllowed(error.category))) {
+          return false;
+        }
+      } else if (ids && ids[0]) {
+        // If this is not an nsIScriptError and we need to do window-based
+        // filtering we skip this message.
+        return false;
+      }
+
+      return true;
+    });
+  },
+
+  /**
+   * Remove the nsIConsoleService listener.
+   */
+  destroy: function () {
+    Services.console.unregisterListener(this);
+    this.listener = this.window = null;
+  },
+};
+
+// The window.console API observer
+
+/**
+ * The window.console API observer. This allows the window.console API messages
+ * to be sent to the remote Web Console instance.
+ *
+ * @constructor
+ * @param nsIDOMWindow window
+ *        Optional - the window object for which we are created. This is used
+ *        for filtering out messages that belong to other windows.
+ * @param object owner
+ *        The owner object must have the following methods:
+ *        - onConsoleAPICall(). This method is invoked with one argument, the
+ *        Console API message that comes from the observer service, whenever
+ *        a relevant console API call is received.
+ * @param object filteringOptions
+ *        Optional - The filteringOptions that this listener should listen to:
+ *        - addonId: filter console messages based on the addonId.
+ */
+function ConsoleAPIListener(window, owner, {addonId} = {}) {
+  this.window = window;
+  this.owner = owner;
+  this.addonId = addonId;
+}
+exports.ConsoleAPIListener = ConsoleAPIListener;
+
+ConsoleAPIListener.prototype =
+{
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver]),
+
+  /**
+   * The content window for which we listen to window.console API calls.
+   * @type nsIDOMWindow
+   */
+  window: null,
+
+  /**
+   * The owner object which is notified of window.console API calls. It must
+   * have a onConsoleAPICall method which is invoked with one argument: the
+   * console API call object that comes from the observer service.
+   *
+   * @type object
+   * @see WebConsoleActor
+   */
+  owner: null,
+
+  /**
+   * The addonId that we listen for. If not null then only messages from this
+   * console will be returned.
+   */
+  addonId: null,
+
+  /**
+   * Initialize the window.console API observer.
+   */
+  init: function () {
+    // Note that the observer is process-wide. We will filter the messages as
+    // needed, see CAL_observe().
+    Services.obs.addObserver(this, "console-api-log-event", false);
+  },
+
+  /**
+   * The console API message observer. When messages are received from the
+   * observer service we forward them to the remote Web Console instance.
+   *
+   * @param object message
+   *        The message object receives from the observer service.
+   * @param string topic
+   *        The message topic received from the observer service.
+   */
+  observe: function (message, topic) {
+    if (!this.owner) {
+      return;
+    }
+
+    // Here, wrappedJSObject is not a security wrapper but a property defined
+    // by the XPCOM component which allows us to unwrap the XPCOM interface and
+    // access the underlying JSObject.
+    let apiMessage = message.wrappedJSObject;
+
+    if (!this.isMessageRelevant(apiMessage)) {
+      return;
+    }
+
+    this.owner.onConsoleAPICall(apiMessage);
+  },
+
+  /**
+   * Given a message, return true if this window should show it and false
+   * if it should be ignored.
+   *
+   * @param message
+   *        The message from the Storage Service
+   * @return bool
+   *         Do we care about this message?
+   */
+  isMessageRelevant: function (message) {
+    let workerType = WebConsoleUtils.getWorkerType(message);
+
+    if (this.window && workerType === "ServiceWorker") {
+      // For messages from Service Workers, message.ID is the
+      // scope, which can be used to determine whether it's controlling
+      // a window.
+      let scope = message.ID;
+
+      if (!swm.shouldReportToWindow(this.window, scope)) {
+        return false;
+      }
+    }
+
+    if (this.window && !workerType) {
+      let msgWindow = Services.wm.getCurrentInnerWindowWithId(message.innerID);
+      if (!msgWindow || !isWindowIncluded(this.window, msgWindow)) {
+        // Not the same window!
+        return false;
+      }
+    }
+
+    if (this.addonId) {
+      // ConsoleAPI.jsm messages contains a consoleID, (and it is currently
+      // used in Addon SDK add-ons), the standard 'console' object
+      // (which is used in regular webpages and in WebExtensions pages)
+      // contains the originAttributes of the source document principal.
+
+      // Filtering based on the originAttributes used by
+      // the Console API object.
+      if (message.originAttributes &&
+          message.originAttributes.addonId == this.addonId) {
+        return true;
+      }
+
+      // Filtering based on the old-style consoleID property used by
+      // the legacy Console JSM module.
+      if (message.consoleID && message.consoleID == `addon/${this.addonId}`) {
+        return true;
+      }
+
+      return false;
+    }
+
+    return true;
+  },
+
+  /**
+   * Get the cached messages for the current inner window and its (i)frames.
+   *
+   * @param boolean [includePrivate=false]
+   *        Tells if you want to also retrieve messages coming from private
+   *        windows. Defaults to false.
+   * @return array
+   *         The array of cached messages.
+   */
+  getCachedMessages: function (includePrivate = false) {
+    let messages = [];
+    let ConsoleAPIStorage = Cc["@mozilla.org/consoleAPI-storage;1"]
+                              .getService(Ci.nsIConsoleAPIStorage);
+
+    // if !this.window, we're in a browser console. Retrieve all events
+    // for filtering based on privacy.
+    if (!this.window) {
+      messages = ConsoleAPIStorage.getEvents();
+    } else {
+      let ids = WebConsoleUtils.getInnerWindowIDsForFrames(this.window);
+      ids.forEach((id) => {
+        messages = messages.concat(ConsoleAPIStorage.getEvents(id));
+      });
+    }
+
+    CONSOLE_WORKER_IDS.forEach((id) => {
+      messages = messages.concat(ConsoleAPIStorage.getEvents(id));
+    });
+
+    messages = messages.filter(msg => {
+      return this.isMessageRelevant(msg);
+    });
+
+    if (includePrivate) {
+      return messages;
+    }
+
+    return messages.filter((m) => !m.private);
+  },
+
+  /**
+   * Destroy the console API listener.
+   */
+  destroy: function () {
+    Services.obs.removeObserver(this, "console-api-log-event");
+    this.window = this.owner = null;
+  },
+};
+
+/**
+ * WebConsole commands manager.
+ *
+ * Defines a set of functions /variables ("commands") that are available from
+ * the Web Console but not from the web page.
+ *
+ */
+var WebConsoleCommands = {
+  _registeredCommands: new Map(),
+  _originalCommands: new Map(),
+
+  /**
+   * @private
+   * Reserved for built-in commands. To register a command from the code of an
+   * add-on, see WebConsoleCommands.register instead.
+   *
+   * @see WebConsoleCommands.register
+   */
+  _registerOriginal: function (name, command) {
+    this.register(name, command);
+    this._originalCommands.set(name, this.getCommand(name));
+  },
+
+  /**
+   * Register a new command.
+   * @param {string} name The command name (exemple: "$")
+   * @param {(function|object)} command The command to register.
+   *  It can be a function so the command is a function (like "$()"),
+   *  or it can also be a property descriptor to describe a getter / value (like
+   *  "$0").
+   *
+   *  The command function or the command getter are passed a owner object as
+   *  their first parameter (see the example below).
+   *
+   *  Note that setters don't work currently and "enumerable" and "configurable"
+   *  are forced to true.
+   *
+   * @example
+   *
+   *   WebConsoleCommands.register("$", function JSTH_$(owner, selector)
+   *   {
+   *     return owner.window.document.querySelector(selector);
+   *   });
+   *
+   *   WebConsoleCommands.register("$0", {
+   *     get: function(owner) {
+   *       return owner.makeDebuggeeValue(owner.selectedNode);
+   *     }
+   *   });
+   */
+  register: function (name, command) {
+    this._registeredCommands.set(name, command);
+  },
+
+  /**
+   * Unregister a command.
+   *
+   * If the command being unregister overrode a built-in command,
+   * the latter is restored.
+   *
+   * @param {string} name The name of the command
+   */
+  unregister: function (name) {
+    this._registeredCommands.delete(name);
+    if (this._originalCommands.has(name)) {
+      this.register(name, this._originalCommands.get(name));
+    }
+  },
+
+  /**
+   * Returns a command by its name.
+   *
+   * @param {string} name The name of the command.
+   *
+   * @return {(function|object)} The command.
+   */
+  getCommand: function (name) {
+    return this._registeredCommands.get(name);
+  },
+
+  /**
+   * Returns true if a command is registered with the given name.
+   *
+   * @param {string} name The name of the command.
+   *
+   * @return {boolean} True if the command is registered.
+   */
+  hasCommand: function (name) {
+    return this._registeredCommands.has(name);
+  },
+};
+
+exports.WebConsoleCommands = WebConsoleCommands;
+
+/*
+ * Built-in commands.
+  *
+  * A list of helper functions used by Firebug can be found here:
+  *   http://getfirebug.com/wiki/index.php/Command_Line_API
+ */
+
+/**
+ * Find a node by ID.
+ *
+ * @param string id
+ *        The ID of the element you want.
+ * @return nsIDOMNode or null
+ *         The result of calling document.querySelector(selector).
+ */
+WebConsoleCommands._registerOriginal("$", function (owner, selector) {
+  return owner.window.document.querySelector(selector);
+});
+
+/**
+ * Find the nodes matching a CSS selector.
+ *
+ * @param string selector
+ *        A string that is passed to window.document.querySelectorAll.
+ * @return nsIDOMNodeList
+ *         Returns the result of document.querySelectorAll(selector).
+ */
+WebConsoleCommands._registerOriginal("$$", function (owner, selector) {
+  let nodes = owner.window.document.querySelectorAll(selector);
+
+  // Calling owner.window.Array.from() doesn't work without accessing the
+  // wrappedJSObject, so just loop through the results instead.
+  let result = new owner.window.Array();
+  for (let i = 0; i < nodes.length; i++) {
+    result.push(nodes[i]);
+  }
+  return result;
+});
+
+/**
+ * Returns the result of the last console input evaluation
+ *
+ * @return object|undefined
+ * Returns last console evaluation or undefined
+ */
+WebConsoleCommands._registerOriginal("$_", {
+  get: function (owner) {
+    return owner.consoleActor.getLastConsoleInputEvaluation();
+  }
+});
+
+/**
+ * Runs an xPath query and returns all matched nodes.
+ *
+ * @param string xPath
+ *        xPath search query to execute.
+ * @param [optional] nsIDOMNode context
+ *        Context to run the xPath query on. Uses window.document if not set.
+ * @return array of nsIDOMNode
+ */
+WebConsoleCommands._registerOriginal("$x", function (owner, xPath, context) {
+  let nodes = new owner.window.Array();
+
+  // Not waiving Xrays, since we want the original Document.evaluate function,
+  // instead of anything that's been redefined.
+  let doc = owner.window.document;
+  context = context || doc;
+
+  let results = doc.evaluate(xPath, context, null,
+                             Ci.nsIDOMXPathResult.ANY_TYPE, null);
+  let node;
+  while ((node = results.iterateNext())) {
+    nodes.push(node);
+  }
+
+  return nodes;
+});
+
+/**
+ * Returns the currently selected object in the highlighter.
+ *
+ * @return Object representing the current selection in the
+ *         Inspector, or null if no selection exists.
+ */
+WebConsoleCommands._registerOriginal("$0", {
+  get: function (owner) {
+    return owner.makeDebuggeeValue(owner.selectedNode);
+  }
+});
+
+/**
+ * Clears the output of the WebConsole.
+ */
+WebConsoleCommands._registerOriginal("clear", function (owner) {
+  owner.helperResult = {
+    type: "clearOutput",
+  };
+});
+
+/**
+ * Clears the input history of the WebConsole.
+ */
+WebConsoleCommands._registerOriginal("clearHistory", function (owner) {
+  owner.helperResult = {
+    type: "clearHistory",
+  };
+});
+
+/**
+ * Returns the result of Object.keys(object).
+ *
+ * @param object object
+ *        Object to return the property names from.
+ * @return array of strings
+ */
+WebConsoleCommands._registerOriginal("keys", function (owner, object) {
+  // Need to waive Xrays so we can iterate functions and accessor properties
+  return Cu.cloneInto(Object.keys(Cu.waiveXrays(object)), owner.window);
+});
+
+/**
+ * Returns the values of all properties on object.
+ *
+ * @param object object
+ *        Object to display the values from.
+ * @return array of string
+ */
+WebConsoleCommands._registerOriginal("values", function (owner, object) {
+  let values = [];
+  // Need to waive Xrays so we can iterate functions and accessor properties
+  let waived = Cu.waiveXrays(object);
+  let names = Object.getOwnPropertyNames(waived);
+
+  for (let name of names) {
+    values.push(waived[name]);
+  }
+
+  return Cu.cloneInto(values, owner.window);
+});
+
+/**
+ * Opens a help window in MDN.
+ */
+WebConsoleCommands._registerOriginal("help", function (owner) {
+  owner.helperResult = { type: "help" };
+});
+
+/**
+ * Change the JS evaluation scope.
+ *
+ * @param DOMElement|string|window window
+ *        The window object to use for eval scope. This can be a string that
+ *        is used to perform document.querySelector(), to find the iframe that
+ *        you want to cd() to. A DOMElement can be given as well, the
+ *        .contentWindow property is used. Lastly, you can directly pass
+ *        a window object. If you call cd() with no arguments, the current
+ *        eval scope is cleared back to its default (the top window).
+ */
+WebConsoleCommands._registerOriginal("cd", function (owner, window) {
+  if (!window) {
+    owner.consoleActor.evalWindow = null;
+    owner.helperResult = { type: "cd" };
+    return;
+  }
+
+  if (typeof window == "string") {
+    window = owner.window.document.querySelector(window);
+  }
+  if (window instanceof Ci.nsIDOMElement && window.contentWindow) {
+    window = window.contentWindow;
+  }
+  if (!(window instanceof Ci.nsIDOMWindow)) {
+    owner.helperResult = {
+      type: "error",
+      message: "cdFunctionInvalidArgument"
+    };
+    return;
+  }
+
+  owner.consoleActor.evalWindow = window;
+  owner.helperResult = { type: "cd" };
+});
+
+/**
+ * Inspects the passed object. This is done by opening the PropertyPanel.
+ *
+ * @param object object
+ *        Object to inspect.
+ */
+WebConsoleCommands._registerOriginal("inspect", function (owner, object) {
+  let dbgObj = owner.makeDebuggeeValue(object);
+  let grip = owner.createValueGrip(dbgObj);
+  owner.helperResult = {
+    type: "inspectObject",
+    input: owner.evalInput,
+    object: grip,
+  };
+});
+
+/**
+ * Prints object to the output.
+ *
+ * @param object object
+ *        Object to print to the output.
+ * @return string
+ */
+WebConsoleCommands._registerOriginal("pprint", function (owner, object) {
+  if (object === null || object === undefined || object === true ||
+      object === false) {
+    owner.helperResult = {
+      type: "error",
+      message: "helperFuncUnsupportedTypeError",
+    };
+    return null;
+  }
+
+  owner.helperResult = { rawOutput: true };
+
+  if (typeof object == "function") {
+    return object + "\n";
+  }
+
+  let output = [];
+
+  let obj = object;
+  for (let name in obj) {
+    let desc = WebConsoleUtils.getPropertyDescriptor(obj, name) || {};
+    if (desc.get || desc.set) {
+      // TODO: Bug 842672 - toolkit/ imports modules from browser/.
+      let getGrip = VariablesView.getGrip(desc.get);
+      let setGrip = VariablesView.getGrip(desc.set);
+      let getString = VariablesView.getString(getGrip);
+      let setString = VariablesView.getString(setGrip);
+      output.push(name + ":", "  get: " + getString, "  set: " + setString);
+    } else {
+      let valueGrip = VariablesView.getGrip(obj[name]);
+      let valueString = VariablesView.getString(valueGrip);
+      output.push(name + ": " + valueString);
+    }
+  }
+
+  return "  " + output.join("\n  ");
+});
+
+/**
+ * Print the String representation of a value to the output, as-is.
+ *
+ * @param any value
+ *        A value you want to output as a string.
+ * @return void
+ */
+WebConsoleCommands._registerOriginal("print", function (owner, value) {
+  owner.helperResult = { rawOutput: true };
+  if (typeof value === "symbol") {
+    return Symbol.prototype.toString.call(value);
+  }
+  // Waiving Xrays here allows us to see a closer representation of the
+  // underlying object. This may execute arbitrary content code, but that
+  // code will run with content privileges, and the result will be rendered
+  // inert by coercing it to a String.
+  return String(Cu.waiveXrays(value));
+});
+
+/**
+ * Copy the String representation of a value to the clipboard.
+ *
+ * @param any value
+ *        A value you want to copy as a string.
+ * @return void
+ */
+WebConsoleCommands._registerOriginal("copy", function (owner, value) {
+  let payload;
+  try {
+    if (value instanceof Ci.nsIDOMElement) {
+      payload = value.outerHTML;
+    } else if (typeof value == "string") {
+      payload = value;
+    } else {
+      payload = JSON.stringify(value, null, "  ");
+    }
+  } catch (ex) {
+    payload = "/* " + ex + " */";
+  }
+  owner.helperResult = {
+    type: "copyValueToClipboard",
+    value: payload,
+  };
+});
+
+/**
+ * (Internal only) Add the bindings to |owner.sandbox|.
+ * This is intended to be used by the WebConsole actor only.
+  *
+  * @param object owner
+  *        The owning object.
+  */
+function addWebConsoleCommands(owner) {
+  if (!owner) {
+    throw new Error("The owner is required");
+  }
+  for (let [name, command] of WebConsoleCommands._registeredCommands) {
+    if (typeof command === "function") {
+      owner.sandbox[name] = command.bind(undefined, owner);
+    } else if (typeof command === "object") {
+      let clone = Object.assign({}, command, {
+        // We force the enumerability and the configurability (so the
+        // WebConsoleActor can reconfigure the property).
+        enumerable: true,
+        configurable: true
+      });
+
+      if (typeof command.get === "function") {
+        clone.get = command.get.bind(undefined, owner);
+      }
+      if (typeof command.set === "function") {
+        clone.set = command.set.bind(undefined, owner);
+      }
+
+      Object.defineProperty(owner.sandbox, name, clone);
+    }
+  }
+}
+
+exports.addWebConsoleCommands = addWebConsoleCommands;
+
+/**
+ * A ReflowObserver that listens for reflow events from the page.
+ * Implements nsIReflowObserver.
+ *
+ * @constructor
+ * @param object window
+ *        The window for which we need to track reflow.
+ * @param object owner
+ *        The listener owner which needs to implement:
+ *        - onReflowActivity(reflowInfo)
+ */
+
+function ConsoleReflowListener(window, listener) {
+  this.docshell = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIWebNavigation)
+                         .QueryInterface(Ci.nsIDocShell);
+  this.listener = listener;
+  this.docshell.addWeakReflowObserver(this);
+}
+
+exports.ConsoleReflowListener = ConsoleReflowListener;
+
+ConsoleReflowListener.prototype =
+{
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIReflowObserver,
+                                         Ci.nsISupportsWeakReference]),
+  docshell: null,
+  listener: null,
+
+  /**
+   * Forward reflow event to listener.
+   *
+   * @param DOMHighResTimeStamp start
+   * @param DOMHighResTimeStamp end
+   * @param boolean interruptible
+   */
+  sendReflow: function (start, end, interruptible) {
+    let frame = components.stack.caller.caller;
+
+    let filename = frame ? frame.filename : null;
+
+    if (filename) {
+      // Because filename could be of the form "xxx.js -> xxx.js -> xxx.js",
+      // we only take the last part.
+      filename = filename.split(" ").pop();
+    }
+
+    this.listener.onReflowActivity({
+      interruptible: interruptible,
+      start: start,
+      end: end,
+      sourceURL: filename,
+      sourceLine: frame ? frame.lineNumber : null,
+      functionName: frame ? frame.name : null
+    });
+  },
+
+  /**
+   * On uninterruptible reflow
+   *
+   * @param DOMHighResTimeStamp start
+   * @param DOMHighResTimeStamp end
+   */
+  reflow: function (start, end) {
+    this.sendReflow(start, end, false);
+  },
+
+  /**
+   * On interruptible reflow
+   *
+   * @param DOMHighResTimeStamp start
+   * @param DOMHighResTimeStamp end
+   */
+  reflowInterruptible: function (start, end) {
+    this.sendReflow(start, end, true);
+  },
+
+  /**
+   * Unregister listener.
+   */
+  destroy: function () {
+    this.docshell.removeWeakReflowObserver(this);
+    this.listener = this.docshell = null;
+  },
+};
diff --git a/devtools/server/actors/utils/webconsole-worker-utils.js b/devtools/server/actors/utils/webconsole-worker-utils.js
new file mode 100644
index 000000000..0c1142967
--- /dev/null
+++ b/devtools/server/actors/utils/webconsole-worker-utils.js
@@ -0,0 +1,20 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft= javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+// XXXworkers This file is loaded on the server side for worker debugging.
+// Since the server is running in the worker thread, it doesn't
+// have access to Services / Components.  This functionality
+// is stubbed out to prevent errors, and will need to implemented
+// for Bug 1209353.
+
+exports.Utils = { L10n: function () {} };
+exports.ConsoleServiceListener = function () {};
+exports.ConsoleAPIListener = function () {};
+exports.addWebConsoleCommands = function () {};
+exports.ConsoleReflowListener = function () {};
+exports.CONSOLE_WORKER_IDS = [];
diff --git a/devtools/server/actors/webaudio.js b/devtools/server/actors/webaudio.js
new file mode 100644
index 000000000..d9035a907
--- /dev/null
+++ b/devtools/server/actors/webaudio.js
@@ -0,0 +1,856 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const {Cc, Ci, Cu, Cr} = require("chrome");
+
+const Services = require("Services");
+
+const events = require("sdk/event/core");
+const promise = require("promise");
+const { on: systemOn, off: systemOff } = require("sdk/system/events");
+const protocol = require("devtools/shared/protocol");
+const { CallWatcherActor } = require("devtools/server/actors/call-watcher");
+const { CallWatcherFront } = require("devtools/shared/fronts/call-watcher");
+const { createValueGrip } = require("devtools/server/actors/object");
+const AutomationTimeline = require("./utils/automation-timeline");
+const { on, once, off, emit } = events;
+const { types, method, Arg, Option, RetVal, preEvent } = protocol;
+const {
+  audionodeSpec,
+  webAudioSpec,
+  AUTOMATION_METHODS,
+  NODE_CREATION_METHODS,
+  NODE_ROUTING_METHODS,
+} = require("devtools/shared/specs/webaudio");
+const { WebAudioFront } = require("devtools/shared/fronts/webaudio");
+const AUDIO_NODE_DEFINITION = require("devtools/server/actors/utils/audionodes.json");
+const ENABLE_AUTOMATION = false;
+const AUTOMATION_GRANULARITY = 2000;
+const AUTOMATION_GRANULARITY_MAX = 6000;
+
+const AUDIO_GLOBALS = [
+  "AudioContext", "AudioNode", "AudioParam"
+];
+
+/**
+ * An Audio Node actor allowing communication to a specific audio node in the
+ * Audio Context graph.
+ */
+var AudioNodeActor = exports.AudioNodeActor = protocol.ActorClassWithSpec(audionodeSpec, {
+  form: function (detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+
+    return {
+      actor: this.actorID, // actorID is set when this is added to a pool
+      type: this.type,
+      source: this.source,
+      bypassable: this.bypassable,
+    };
+  },
+
+  /**
+   * Create the Audio Node actor.
+   *
+   * @param DebuggerServerConnection conn
+   *        The server connection.
+   * @param AudioNode node
+   *        The AudioNode that was created.
+   */
+  initialize: function (conn, node) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+
+    // Store ChromeOnly property `id` to identify AudioNode,
+    // rather than storing a strong reference, and store a weak
+    // ref to underlying node for controlling.
+    this.nativeID = node.id;
+    this.node = Cu.getWeakReference(node);
+
+    // Stores the AutomationTimelines for this node's AudioParams.
+    this.automation = {};
+
+    try {
+      this.type = getConstructorName(node);
+    } catch (e) {
+      this.type = "";
+    }
+
+    this.source = !!AUDIO_NODE_DEFINITION[this.type].source;
+    this.bypassable = !AUDIO_NODE_DEFINITION[this.type].unbypassable;
+
+    // Create automation timelines for all AudioParams
+    Object.keys(AUDIO_NODE_DEFINITION[this.type].properties || {})
+      .filter(isAudioParam.bind(null, node))
+      .forEach(paramName => {
+        this.automation[paramName] = new AutomationTimeline(node[paramName].defaultValue);
+      });
+  },
+
+  /**
+   * Returns the string name of the audio type.
+   *
+   * DEPRECATED: Use `audionode.type` instead, left here for legacy reasons.
+   */
+  getType: function () {
+    return this.type;
+  },
+
+  /**
+   * Returns a boolean indicating if the AudioNode has been "bypassed",
+   * via `AudioNodeActor#bypass` method.
+   *
+   * @return Boolean
+   */
+  isBypassed: function () {
+    let node = this.node.get();
+    if (node === null) {
+      return false;
+    }
+
+    // Cast to boolean incase `passThrough` is undefined,
+    // like for AudioDestinationNode
+    return !!node.passThrough;
+  },
+
+  /**
+   * Takes a boolean, either enabling or disabling the "passThrough" option
+   * on an AudioNode. If a node is bypassed, an effects processing node (like gain, biquad),
+   * will allow the audio stream to pass through the node, unaffected. Returns
+   * the bypass state of the node.
+   *
+   * @param Boolean enable
+   *        Whether the bypass value should be set on or off.
+   * @return Boolean
+   */
+  bypass: function (enable) {
+    let node = this.node.get();
+
+    if (node === null) {
+      return;
+    }
+
+    if (this.bypassable) {
+      node.passThrough = enable;
+    }
+
+    return this.isBypassed();
+  },
+
+  /**
+   * Changes a param on the audio node. Responds with either `undefined`
+   * on success, or a description of the error upon param set failure.
+   *
+   * @param String param
+   *        Name of the AudioParam to change.
+   * @param String value
+   *        Value to change AudioParam to.
+   */
+  setParam: function (param, value) {
+    let node = this.node.get();
+
+    if (node === null) {
+      return CollectedAudioNodeError();
+    }
+
+    try {
+      if (isAudioParam(node, param)) {
+        node[param].value = value;
+        this.automation[param].setValue(value);
+      }
+      else {
+        node[param] = value;
+      }
+      return undefined;
+    } catch (e) {
+      return constructError(e);
+    }
+  },
+
+  /**
+   * Gets a param on the audio node.
+   *
+   * @param String param
+   *        Name of the AudioParam to fetch.
+   */
+  getParam: function (param) {
+    let node = this.node.get();
+
+    if (node === null) {
+      return CollectedAudioNodeError();
+    }
+
+    // Check to see if it's an AudioParam -- if so,
+    // return the `value` property of the parameter.
+    let value = isAudioParam(node, param) ? node[param].value : node[param];
+
+    // Return the grip form of the value; at this time,
+    // there shouldn't be any non-primitives at the moment, other than
+    // AudioBuffer or Float32Array references and the like,
+    // so this just formats the value to be displayed in the VariablesView,
+    // without using real grips and managing via actor pools.
+    let grip = createValueGrip(value, null, createObjectGrip);
+
+    return grip;
+  },
+
+  /**
+   * Get an object containing key-value pairs of additional attributes
+   * to be consumed by a front end, like if a property should be read only,
+   * or is a special type (Float32Array, Buffer, etc.)
+   *
+   * @param String param
+   *        Name of the AudioParam whose flags are desired.
+   */
+  getParamFlags: function (param) {
+    return ((AUDIO_NODE_DEFINITION[this.type] || {}).properties || {})[param];
+  },
+
+  /**
+   * Get an array of objects each containing a `param` and `value` property,
+   * corresponding to a property name and current value of the audio node.
+   */
+  getParams: function (param) {
+    let props = Object.keys(AUDIO_NODE_DEFINITION[this.type].properties || {});
+    return props.map(prop =>
+      ({ param: prop, value: this.getParam(prop), flags: this.getParamFlags(prop) }));
+  },
+
+  /**
+   * Connects this audionode to an AudioParam via `node.connect(param)`.
+   */
+  connectParam: function (destActor, paramName, output) {
+    let srcNode = this.node.get();
+    let destNode = destActor.node.get();
+
+    if (srcNode === null || destNode === null) {
+      return CollectedAudioNodeError();
+    }
+
+    try {
+      // Connect via the unwrapped node, so we can call the
+      // patched method that fires the webaudio actor's `connect-param` event.
+      // Connect directly to the wrapped `destNode`, otherwise
+      // the patched method thinks this is a new node and won't be
+      // able to find it in `_nativeToActorID`.
+      XPCNativeWrapper.unwrap(srcNode).connect(destNode[paramName], output);
+    } catch (e) {
+      return constructError(e);
+    }
+  },
+
+  /**
+   * Connects this audionode to another via `node.connect(dest)`.
+   */
+  connectNode: function (destActor, output, input) {
+    let srcNode = this.node.get();
+    let destNode = destActor.node.get();
+
+    if (srcNode === null || destNode === null) {
+      return CollectedAudioNodeError();
+    }
+
+    try {
+      // Connect via the unwrapped node, so we can call the
+      // patched method that fires the webaudio actor's `connect-node` event.
+      // Connect directly to the wrapped `destNode`, otherwise
+      // the patched method thinks this is a new node and won't be
+      // able to find it in `_nativeToActorID`.
+      XPCNativeWrapper.unwrap(srcNode).connect(destNode, output, input);
+    } catch (e) {
+      return constructError(e);
+    }
+  },
+
+  /**
+   * Disconnects this audionode from all connections via `node.disconnect()`.
+   */
+  disconnect: function (destActor, output) {
+    let node = this.node.get();
+
+    if (node === null) {
+      return CollectedAudioNodeError();
+    }
+
+    try {
+      // Disconnect via the unwrapped node, so we can call the
+      // patched method that fires the webaudio actor's `disconnect` event.
+      XPCNativeWrapper.unwrap(node).disconnect(output);
+    } catch (e) {
+      return constructError(e);
+    }
+  },
+
+  getAutomationData: function (paramName) {
+    let timeline = this.automation[paramName];
+    if (!timeline) {
+      return null;
+    }
+
+    let events = timeline.events;
+    let values = [];
+    let i = 0;
+
+    if (!timeline.events.length) {
+      return { events, values };
+    }
+
+    let firstEvent = events[0];
+    let lastEvent = events[timeline.events.length - 1];
+    // `setValueCurveAtTime` will have a duration value -- other
+    // events will have duration of `0`.
+    let timeDelta = (lastEvent.time + lastEvent.duration) - firstEvent.time;
+    let scale = timeDelta / AUTOMATION_GRANULARITY;
+
+    for (; i < AUTOMATION_GRANULARITY; i++) {
+      let delta = firstEvent.time + (i * scale);
+      let value = timeline.getValueAtTime(delta);
+      values.push({ delta, value });
+    }
+
+    // If the last event is setTargetAtTime, the automation
+    // doesn't actually begin until the event's time, and exponentially
+    // approaches the target value. In this case, we add more values
+    // until we're "close enough" to the target.
+    if (lastEvent.type === "setTargetAtTime") {
+      for (; i < AUTOMATION_GRANULARITY_MAX; i++) {
+        let delta = firstEvent.time + (++i * scale);
+        let value = timeline.getValueAtTime(delta);
+        values.push({ delta, value });
+      }
+    }
+
+    return { events, values };
+  },
+
+  /**
+   * Called via WebAudioActor, registers an automation event
+   * for the AudioParam called.
+   *
+   * @param String paramName
+   *        Name of the AudioParam.
+   * @param String eventName
+   *        Name of the automation event called.
+   * @param Array args
+   *        Arguments passed into the automation call.
+   */
+  addAutomationEvent: function (paramName, eventName, args = []) {
+    let node = this.node.get();
+    let timeline = this.automation[paramName];
+
+    if (node === null) {
+      return CollectedAudioNodeError();
+    }
+
+    if (!timeline || !node[paramName][eventName]) {
+      return InvalidCommandError();
+    }
+
+    try {
+      // Using the unwrapped node and parameter, the corresponding
+      // WebAudioActor event will be fired, subsequently calling
+      // `_recordAutomationEvent`. Some finesse is required to handle
+      // the cast of TypedArray arguments over the protocol, which is
+      // taken care of below. The event will cast the argument back
+      // into an array to be broadcasted from WebAudioActor, but the
+      // double-casting will only occur when starting from `addAutomationEvent`,
+      // which is only used in tests.
+      let param = XPCNativeWrapper.unwrap(node[paramName]);
+      let contentGlobal = Cu.getGlobalForObject(param);
+      let contentArgs = Cu.cloneInto(args, contentGlobal);
+
+      // If calling `setValueCurveAtTime`, the first argument
+      // is a Float32Array, which won't be able to be serialized
+      // over the protocol. Cast a normal array to a Float32Array here.
+      if (eventName === "setValueCurveAtTime") {
+        // Create a Float32Array from the content, seeding with an array
+        // from the same scope.
+        let curve = new contentGlobal.Float32Array(contentArgs[0]);
+        contentArgs[0] = curve;
+      }
+
+      // Apply the args back from the content scope, which is necessary
+      // due to the method wrapping changing in bug 1130901 to be exported
+      // directly to the content scope.
+      param[eventName].apply(param, contentArgs);
+    } catch (e) {
+      return constructError(e);
+    }
+  },
+
+  /**
+   * Registers the automation event in the AudioNodeActor's
+   * internal timeline. Called when setting automation via
+   * `addAutomationEvent`, or from the WebAudioActor's listening
+   * to the event firing via content.
+   *
+   * @param String paramName
+   *        Name of the AudioParam.
+   * @param String eventName
+   *        Name of the automation event called.
+   * @param Array args
+   *        Arguments passed into the automation call.
+   */
+  _recordAutomationEvent: function (paramName, eventName, args) {
+    let timeline = this.automation[paramName];
+    timeline[eventName].apply(timeline, args);
+  }
+});
+
+/**
+ * The Web Audio Actor handles simple interaction with an AudioContext
+ * high-level methods. After instantiating this actor, you'll need to set it
+ * up by calling setup().
+ */
+var WebAudioActor = exports.WebAudioActor = protocol.ActorClassWithSpec(webAudioSpec, {
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.tabActor = tabActor;
+
+    this._onContentFunctionCall = this._onContentFunctionCall.bind(this);
+
+    // Store ChromeOnly ID (`nativeID` property on AudioNodeActor) mapped
+    // to the associated actorID, so we don't have to expose `nativeID`
+    // to the client in any way.
+    this._nativeToActorID = new Map();
+
+    this._onDestroyNode = this._onDestroyNode.bind(this);
+    this._onGlobalDestroyed = this._onGlobalDestroyed.bind(this);
+    this._onGlobalCreated = this._onGlobalCreated.bind(this);
+  },
+
+  destroy: function (conn) {
+    protocol.Actor.prototype.destroy.call(this, conn);
+    this.finalize();
+  },
+
+  /**
+   * Returns definition of all AudioNodes, such as AudioParams, and
+   * flags.
+   */
+  getDefinition: function () {
+    return AUDIO_NODE_DEFINITION;
+  },
+
+  /**
+   * Starts waiting for the current tab actor's document global to be
+   * created, in order to instrument the Canvas context and become
+   * aware of everything the content does with Web Audio.
+   *
+   * See ContentObserver and WebAudioInstrumenter for more details.
+   */
+  setup: function ({ reload }) {
+    // Used to track when something is happening with the web audio API
+    // the first time, to ultimately fire `start-context` event
+    this._firstNodeCreated = false;
+
+    // Clear out stored nativeIDs on reload as we do not want to track
+    // AudioNodes that are no longer on this document.
+    this._nativeToActorID.clear();
+
+    if (this._initialized) {
+      if (reload) {
+        this.tabActor.window.location.reload();
+      }
+      return;
+    }
+
+    this._initialized = true;
+
+    this._callWatcher = new CallWatcherActor(this.conn, this.tabActor);
+    this._callWatcher.onCall = this._onContentFunctionCall;
+    this._callWatcher.setup({
+      tracedGlobals: AUDIO_GLOBALS,
+      startRecording: true,
+      performReload: reload,
+      holdWeak: true,
+      storeCalls: false
+    });
+    // Bind to `window-ready` so we can reenable recording on the
+    // call watcher
+    on(this.tabActor, "window-ready", this._onGlobalCreated);
+    // Bind to the `window-destroyed` event so we can unbind events between
+    // the global destruction and the `finalize` cleanup method on the actor.
+    on(this.tabActor, "window-destroyed", this._onGlobalDestroyed);
+  },
+
+  /**
+   * Invoked whenever an instrumented function is called, like an AudioContext
+   * method or an AudioNode method.
+   */
+  _onContentFunctionCall: function (functionCall) {
+    let { name } = functionCall.details;
+
+    // All Web Audio nodes inherit from AudioNode's prototype, so
+    // hook into the `connect` and `disconnect` methods
+    if (WebAudioFront.NODE_ROUTING_METHODS.has(name)) {
+      this._handleRoutingCall(functionCall);
+    }
+    else if (WebAudioFront.NODE_CREATION_METHODS.has(name)) {
+      this._handleCreationCall(functionCall);
+    }
+    else if (ENABLE_AUTOMATION && WebAudioFront.AUTOMATION_METHODS.has(name)) {
+      this._handleAutomationCall(functionCall);
+    }
+  },
+
+  _handleRoutingCall: function (functionCall) {
+    let { caller, args, name } = functionCall.details;
+    let source = caller;
+    let dest = args[0];
+    let isAudioParam = dest ? getConstructorName(dest) === "AudioParam" : false;
+
+    // audionode.connect(param)
+    if (name === "connect" && isAudioParam) {
+      this._onConnectParam(source, dest);
+    }
+    // audionode.connect(node)
+    else if (name === "connect") {
+      this._onConnectNode(source, dest);
+    }
+    // audionode.disconnect()
+    else if (name === "disconnect") {
+      this._onDisconnectNode(source);
+    }
+  },
+
+  _handleCreationCall: function (functionCall) {
+    let { caller, result } = functionCall.details;
+    // Keep track of the first node created, so we can alert
+    // the front end that an audio context is being used since
+    // we're not hooking into the constructor itself, just its
+    // instance's methods.
+    if (!this._firstNodeCreated) {
+      // Fire the start-up event if this is the first node created
+      // and trigger a `create-node` event for the context destination
+      this._onStartContext();
+      this._onCreateNode(caller.destination);
+      this._firstNodeCreated = true;
+    }
+    this._onCreateNode(result);
+  },
+
+  _handleAutomationCall: function (functionCall) {
+    let { caller, name, args } = functionCall.details;
+    let wrappedParam = new XPCNativeWrapper(caller);
+
+    // Sanitize arguments, as these should all be numbers,
+    // with the exception of a TypedArray, which needs
+    // casted to an Array
+    args = sanitizeAutomationArgs(args);
+
+    let nodeActor = this._getActorByNativeID(wrappedParam._parentID);
+    nodeActor._recordAutomationEvent(wrappedParam._paramName, name, args);
+
+    this._onAutomationEvent({
+      node: nodeActor,
+      paramName: wrappedParam._paramName,
+      eventName: name,
+      args: args
+    });
+  },
+
+  /**
+   * Stops listening for document global changes and puts this actor
+   * to hibernation. This method is called automatically just before the
+   * actor is destroyed.
+   */
+  finalize: function () {
+    if (!this._initialized) {
+      return;
+    }
+    this._initialized = false;
+    systemOff("webaudio-node-demise", this._onDestroyNode);
+
+    off(this.tabActor, "window-destroyed", this._onGlobalDestroyed);
+    off(this.tabActor, "window-ready", this._onGlobalCreated);
+    this.tabActor = null;
+    this._nativeToActorID = null;
+    this._callWatcher.eraseRecording();
+    this._callWatcher.finalize();
+    this._callWatcher = null;
+  },
+
+  /**
+   * Helper for constructing an AudioNodeActor, assigning to
+   * internal weak map, and tracking via `manage` so it is assigned
+   * an `actorID`.
+   */
+  _constructAudioNode: function (node) {
+    // Ensure AudioNode is wrapped.
+    node = new XPCNativeWrapper(node);
+
+    this._instrumentParams(node);
+
+    let actor = new AudioNodeActor(this.conn, node);
+    this.manage(actor);
+    this._nativeToActorID.set(node.id, actor.actorID);
+    return actor;
+  },
+
+  /**
+   * Takes an XrayWrapper node, and attaches the node's `nativeID`
+   * to the AudioParams as `_parentID`, as well as the the type of param
+   * as a string on `_paramName`.
+   */
+  _instrumentParams: function (node) {
+    let type = getConstructorName(node);
+    Object.keys(AUDIO_NODE_DEFINITION[type].properties || {})
+      .filter(isAudioParam.bind(null, node))
+      .forEach(paramName => {
+        let param = node[paramName];
+        param._parentID = node.id;
+        param._paramName = paramName;
+      });
+  },
+
+  /**
+   * Takes an AudioNode and returns the stored actor for it.
+   * In some cases, we won't have an actor stored (for example,
+   * connecting to an AudioDestinationNode, since it's implicitly
+   * created), so make a new actor and store that.
+   */
+  _getActorByNativeID: function (nativeID) {
+    // Ensure we have a Number, rather than a string
+    // return via notification.
+    nativeID = ~~nativeID;
+
+    let actorID = this._nativeToActorID.get(nativeID);
+    let actor = actorID != null ? this.conn.getActor(actorID) : null;
+    return actor;
+  },
+
+  /**
+   * Called on first audio node creation, signifying audio context usage
+   */
+  _onStartContext: function () {
+    systemOn("webaudio-node-demise", this._onDestroyNode);
+    emit(this, "start-context");
+  },
+
+  /**
+   * Called when one audio node is connected to another.
+   */
+  _onConnectNode: function (source, dest) {
+    let sourceActor = this._getActorByNativeID(source.id);
+    let destActor = this._getActorByNativeID(dest.id);
+
+    emit(this, "connect-node", {
+      source: sourceActor,
+      dest: destActor
+    });
+  },
+
+  /**
+   * Called when an audio node is connected to an audio param.
+   */
+  _onConnectParam: function (source, param) {
+    let sourceActor = this._getActorByNativeID(source.id);
+    let destActor = this._getActorByNativeID(param._parentID);
+    emit(this, "connect-param", {
+      source: sourceActor,
+      dest: destActor,
+      param: param._paramName
+    });
+  },
+
+  /**
+   * Called when an audio node is disconnected.
+   */
+  _onDisconnectNode: function (node) {
+    let actor = this._getActorByNativeID(node.id);
+    emit(this, "disconnect-node", actor);
+  },
+
+  /**
+   * Called when a parameter changes on an audio node
+   */
+  _onParamChange: function (node, param, value) {
+    let actor = this._getActorByNativeID(node.id);
+    emit(this, "param-change", {
+      source: actor,
+      param: param,
+      value: value
+    });
+  },
+
+  /**
+   * Called on node creation.
+   */
+  _onCreateNode: function (node) {
+    let actor = this._constructAudioNode(node);
+    emit(this, "create-node", actor);
+  },
+
+  /** Called when `webaudio-node-demise` is triggered,
+   * and emits the associated actor to the front if found.
+   */
+  _onDestroyNode: function ({data}) {
+    // Cast to integer.
+    let nativeID = ~~data;
+
+    let actor = this._getActorByNativeID(nativeID);
+
+    // If actorID exists, emit; in the case where we get demise
+    // notifications for a document that no longer exists,
+    // the mapping should not be found, so we do not emit an event.
+    if (actor) {
+      this._nativeToActorID.delete(nativeID);
+      emit(this, "destroy-node", actor);
+    }
+  },
+
+  /**
+   * Ensures that the new global has recording on
+   * so we can proxy the function calls.
+   */
+  _onGlobalCreated: function () {
+    // Used to track when something is happening with the web audio API
+    // the first time, to ultimately fire `start-context` event
+    this._firstNodeCreated = false;
+
+    // Clear out stored nativeIDs on reload as we do not want to track
+    // AudioNodes that are no longer on this document.
+    this._nativeToActorID.clear();
+
+    this._callWatcher.resumeRecording();
+  },
+
+  /**
+   * Fired when an automation event is added to an AudioNode.
+   */
+  _onAutomationEvent: function ({node, paramName, eventName, args}) {
+    emit(this, "automation-event", {
+      node: node,
+      paramName: paramName,
+      eventName: eventName,
+      args: args
+    });
+  },
+
+  /**
+   * Called when the underlying ContentObserver fires `global-destroyed`
+   * so we can cleanup some things between the global being destroyed and
+   * when the actor's `finalize` method gets called.
+   */
+  _onGlobalDestroyed: function ({id}) {
+    if (this._callWatcher._tracedWindowId !== id) {
+      return;
+    }
+
+    if (this._nativeToActorID) {
+      this._nativeToActorID.clear();
+    }
+    systemOff("webaudio-node-demise", this._onDestroyNode);
+  }
+});
+
+/**
+ * Determines whether or not property is an AudioParam.
+ *
+ * @param AudioNode node
+ *        An AudioNode.
+ * @param String prop
+ *        Property of `node` to evaluate to see if it's an AudioParam.
+ * @return Boolean
+ */
+function isAudioParam(node, prop) {
+  return !!(node[prop] && /AudioParam/.test(node[prop].toString()));
+}
+
+/**
+ * Takes an `Error` object and constructs a JSON-able response
+ *
+ * @param Error err
+ *        A TypeError, RangeError, etc.
+ * @return Object
+ */
+function constructError(err) {
+  return {
+    message: err.message,
+    type: err.constructor.name
+  };
+}
+
+/**
+ * Creates and returns a JSON-able response used to indicate
+ * attempt to access an AudioNode that has been GC'd.
+ *
+ * @return Object
+ */
+function CollectedAudioNodeError() {
+  return {
+    message: "AudioNode has been garbage collected and can no longer be reached.",
+    type: "UnreachableAudioNode"
+  };
+}
+
+function InvalidCommandError() {
+  return {
+    message: "The command on AudioNode is invalid.",
+    type: "InvalidCommand"
+  };
+}
+
+/**
+ * Takes an object and converts it's `toString()` form, like
+ * "[object OscillatorNode]" or "[object Float32Array]",
+ * or XrayWrapper objects like "[object XrayWrapper [object Array]]"
+ * to a string of just the constructor name, like "OscillatorNode",
+ * or "Float32Array".
+ */
+function getConstructorName(obj) {
+  return Object.prototype.toString.call(obj).match(/\[object ([^\[\]]*)\]\]?$/)[1];
+}
+
+/**
+ * Create a grip-like object to pass in renderable information
+ * to the front-end for things like Float32Arrays, AudioBuffers,
+ * without tracking them in an actor pool.
+ */
+function createObjectGrip(value) {
+  return {
+    type: "object",
+    preview: {
+      kind: "ObjectWithText",
+      text: ""
+    },
+    class: getConstructorName(value)
+  };
+}
+
+/**
+ * Converts all TypedArrays of the array that cannot
+ * be passed over the wire into a normal Array equivilent.
+ */
+function sanitizeAutomationArgs(args) {
+  return args.reduce((newArgs, el) => {
+    newArgs.push(typeof el === "object" && getConstructorName(el) === "Float32Array" ? castToArray(el) : el);
+    return newArgs;
+  }, []);
+}
+
+/**
+ * Casts TypedArray to a normal array via a
+ * new scope.
+ */
+function castToArray(typedArray) {
+  // The Xray machinery for TypedArrays denies indexed access on the grounds
+  // that it's slow, and advises callers to do a structured clone instead.
+  let global = Cu.getGlobalForObject(this);
+  let safeView = Cu.cloneInto(typedArray.subarray(), global);
+  return copyInto([], safeView);
+}
+
+/**
+ * Copies values of an array-like `source` into
+ * a similarly array-like `dest`.
+ */
+function copyInto(dest, source) {
+  for (let i = 0; i < source.length; i++) {
+    dest[i] = source[i];
+  }
+  return dest;
+}
diff --git a/devtools/server/actors/webbrowser.js b/devtools/server/actors/webbrowser.js
new file mode 100644
index 000000000..0edcdc187
--- /dev/null
+++ b/devtools/server/actors/webbrowser.js
@@ -0,0 +1,2529 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/* global XPCNativeWrapper */
+
+var { Ci, Cu, Cr } = require("chrome");
+var Services = require("Services");
+var { XPCOMUtils } = require("resource://gre/modules/XPCOMUtils.jsm");
+var promise = require("promise");
+var {
+  ActorPool, createExtraActors, appendExtraActors, GeneratedLocation
+} = require("devtools/server/actors/common");
+var { DebuggerServer } = require("devtools/server/main");
+var DevToolsUtils = require("devtools/shared/DevToolsUtils");
+var { assert } = DevToolsUtils;
+var { TabSources } = require("./utils/TabSources");
+var makeDebugger = require("./utils/make-debugger");
+
+loader.lazyRequireGetter(this, "RootActor", "devtools/server/actors/root", true);
+loader.lazyRequireGetter(this, "ThreadActor", "devtools/server/actors/script", true);
+loader.lazyRequireGetter(this, "unwrapDebuggerObjectGlobal", "devtools/server/actors/script", true);
+loader.lazyRequireGetter(this, "BrowserAddonActor", "devtools/server/actors/addon", true);
+loader.lazyRequireGetter(this, "WebExtensionActor", "devtools/server/actors/webextension", true);
+loader.lazyRequireGetter(this, "WorkerActorList", "devtools/server/actors/worker", true);
+loader.lazyRequireGetter(this, "ServiceWorkerRegistrationActorList", "devtools/server/actors/worker", true);
+loader.lazyRequireGetter(this, "ProcessActorList", "devtools/server/actors/process", true);
+loader.lazyImporter(this, "AddonManager", "resource://gre/modules/AddonManager.jsm");
+loader.lazyImporter(this, "ExtensionContent", "resource://gre/modules/ExtensionContent.jsm");
+
+// Assumptions on events module:
+// events needs to be dispatched synchronously,
+// by calling the listeners in the order or registration.
+loader.lazyRequireGetter(this, "events", "sdk/event/core");
+
+loader.lazyRequireGetter(this, "StyleSheetActor", "devtools/server/actors/stylesheets", true);
+
+function getWindowID(window) {
+  return window.QueryInterface(Ci.nsIInterfaceRequestor)
+               .getInterface(Ci.nsIDOMWindowUtils)
+               .currentInnerWindowID;
+}
+
+function getDocShellChromeEventHandler(docShell) {
+  let handler = docShell.chromeEventHandler;
+  if (!handler) {
+    try {
+      // Toplevel xul window's docshell doesn't have chromeEventHandler
+      // attribute. The chrome event handler is just the global window object.
+      handler = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                        .getInterface(Ci.nsIDOMWindow);
+    } catch (e) {
+      // ignore
+    }
+  }
+  return handler;
+}
+
+function getChildDocShells(parentDocShell) {
+  let docShellsEnum = parentDocShell.getDocShellEnumerator(
+    Ci.nsIDocShellTreeItem.typeAll,
+    Ci.nsIDocShell.ENUMERATE_FORWARDS
+  );
+
+  let docShells = [];
+  while (docShellsEnum.hasMoreElements()) {
+    let docShell = docShellsEnum.getNext();
+    docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+            .getInterface(Ci.nsIWebProgress);
+    docShells.push(docShell);
+  }
+  return docShells;
+}
+
+exports.getChildDocShells = getChildDocShells;
+
+/**
+ * Browser-specific actors.
+ */
+
+function getInnerId(window) {
+  return window.QueryInterface(Ci.nsIInterfaceRequestor)
+               .getInterface(Ci.nsIDOMWindowUtils).currentInnerWindowID;
+}
+
+/**
+ * Yield all windows of type |windowType|, from the oldest window to the
+ * youngest, using nsIWindowMediator::getEnumerator. We're usually
+ * interested in "navigator:browser" windows.
+ */
+function* allAppShellDOMWindows(windowType) {
+  let e = Services.wm.getEnumerator(windowType);
+  while (e.hasMoreElements()) {
+    yield e.getNext();
+  }
+}
+
+exports.allAppShellDOMWindows = allAppShellDOMWindows;
+
+/**
+ * Retrieve the window type of the top-level window |window|.
+ */
+function appShellDOMWindowType(window) {
+  /* This is what nsIWindowMediator's enumerator checks. */
+  return window.document.documentElement.getAttribute("windowtype");
+}
+
+/**
+ * Send Debugger:Shutdown events to all "navigator:browser" windows.
+ */
+function sendShutdownEvent() {
+  for (let win of allAppShellDOMWindows(DebuggerServer.chromeWindowType)) {
+    let evt = win.document.createEvent("Event");
+    evt.initEvent("Debugger:Shutdown", true, false);
+    win.document.documentElement.dispatchEvent(evt);
+  }
+}
+
+exports.sendShutdownEvent = sendShutdownEvent;
+
+/**
+ * Construct a root actor appropriate for use in a server running in a
+ * browser. The returned root actor:
+ * - respects the factories registered with DebuggerServer.addGlobalActor,
+ * - uses a BrowserTabList to supply tab actors,
+ * - sends all navigator:browser window documents a Debugger:Shutdown event
+ *   when it exits.
+ *
+ * * @param connection DebuggerServerConnection
+ *          The conection to the client.
+ */
+function createRootActor(connection) {
+  return new RootActor(connection, {
+    tabList: new BrowserTabList(connection),
+    addonList: new BrowserAddonList(connection),
+    workerList: new WorkerActorList(connection, {}),
+    serviceWorkerRegistrationList:
+      new ServiceWorkerRegistrationActorList(connection),
+    processList: new ProcessActorList(),
+    globalActorFactories: DebuggerServer.globalActorFactories,
+    onShutdown: sendShutdownEvent
+  });
+}
+
+/**
+ * A live list of BrowserTabActors representing the current browser tabs,
+ * to be provided to the root actor to answer 'listTabs' requests.
+ *
+ * This object also takes care of listening for TabClose events and
+ * onCloseWindow notifications, and exiting the BrowserTabActors concerned.
+ *
+ * (See the documentation for RootActor for the definition of the "live
+ * list" interface.)
+ *
+ * @param connection DebuggerServerConnection
+ *     The connection in which this list's tab actors may participate.
+ *
+ * Some notes:
+ *
+ * This constructor is specific to the desktop browser environment; it
+ * maintains the tab list by tracking XUL windows and their XUL documents'
+ * "tabbrowser", "tab", and "browser" elements. What's entailed in maintaining
+ * an accurate list of open tabs in this context?
+ *
+ * - Opening and closing XUL windows:
+ *
+ * An nsIWindowMediatorListener is notified when new XUL windows (i.e., desktop
+ * windows) are opened and closed. It is not notified of individual content
+ * browser tabs coming and going within such a XUL window. That seems
+ * reasonable enough; it's concerned with XUL windows, not tab elements in the
+ * window's XUL document.
+ *
+ * However, even if we attach TabOpen and TabClose event listeners to each XUL
+ * window as soon as it is created:
+ *
+ * - we do not receive a TabOpen event for the initial empty tab of a new XUL
+ *   window; and
+ *
+ * - we do not receive TabClose events for the tabs of a XUL window that has
+ *   been closed.
+ *
+ * This means that TabOpen and TabClose events alone are not sufficient to
+ * maintain an accurate list of live tabs and mark tab actors as closed
+ * promptly. Our nsIWindowMediatorListener onCloseWindow handler must find and
+ * exit all actors for tabs that were in the closing window.
+ *
+ * Since this is a bit hairy, we don't make each individual attached tab actor
+ * responsible for noticing when it has been closed; we watch for that, and
+ * promise to call each actor's 'exit' method when it's closed, regardless of
+ * how we learn the news.
+ *
+ * - nsIWindowMediator locks
+ *
+ * nsIWindowMediator holds a lock protecting its list of top-level windows
+ * while it calls nsIWindowMediatorListener methods. nsIWindowMediator's
+ * GetEnumerator method also tries to acquire that lock. Thus, enumerating
+ * windows from within a listener method deadlocks (bug 873589). Rah. One
+ * can sometimes work around this by leaving the enumeration for a later
+ * tick.
+ *
+ * - Dragging tabs between windows:
+ *
+ * When a tab is dragged from one desktop window to another, we receive a
+ * TabOpen event for the new tab, and a TabClose event for the old tab; tab XUL
+ * elements do not really move from one document to the other (although their
+ * linked browser's content window objects do).
+ *
+ * However, while we could thus assume that each tab stays with the XUL window
+ * it belonged to when it was created, I'm not sure this is behavior one should
+ * rely upon. When a XUL window is closed, we take the less efficient, more
+ * conservative approach of simply searching the entire table for actors that
+ * belong to the closing XUL window, rather than trying to somehow track which
+ * XUL window each tab belongs to.
+ *
+ * - Title changes:
+ *
+ * For tabs living in the child process, we listen for DOMTitleChange message
+ * via the top-level window's message manager. Doing this also allows listening
+ * for title changes on Fennec.
+ * But as these messages aren't sent for tabs loaded in the parent process,
+ * we also listen for TabAttrModified event, which is fired only on Firefox
+ * desktop.
+ */
+function BrowserTabList(connection) {
+  this._connection = connection;
+
+  /*
+   * The XUL document of a tabbed browser window has "tab" elements, whose
+   * 'linkedBrowser' JavaScript properties are "browser" elements; those
+   * browsers' 'contentWindow' properties are wrappers on the tabs' content
+   * window objects.
+   *
+   * This map's keys are "browser" XUL elements; it maps each browser element
+   * to the tab actor we've created for its content window, if we've created
+   * one. This map serves several roles:
+   *
+   * - During iteration, we use it to find actors we've created previously.
+   *
+   * - On a TabClose event, we use it to find the tab's actor and exit it.
+   *
+   * - When the onCloseWindow handler is called, we iterate over it to find all
+   *   tabs belonging to the closing XUL window, and exit them.
+   *
+   * - When it's empty, and the onListChanged hook is null, we know we can
+   *   stop listening for events and notifications.
+   *
+   * We listen for TabClose events and onCloseWindow notifications in order to
+   * send onListChanged notifications, but also to tell actors when their
+   * referent has gone away and remove entries for dead browsers from this map.
+   * If that code is working properly, neither this map nor the actors in it
+   * should ever hold dead tabs alive.
+   */
+  this._actorByBrowser = new Map();
+
+  /* The current onListChanged handler, or null. */
+  this._onListChanged = null;
+
+  /*
+   * True if we've been iterated over since we last called our onListChanged
+   * hook.
+   */
+  this._mustNotify = false;
+
+  /* True if we're testing, and should throw if consistency checks fail. */
+  this._testing = false;
+}
+
+BrowserTabList.prototype.constructor = BrowserTabList;
+
+/**
+ * Get the selected browser for the given navigator:browser window.
+ * @private
+ * @param window nsIChromeWindow
+ *        The navigator:browser window for which you want the selected browser.
+ * @return nsIDOMElement|null
+ *         The currently selected xul:browser element, if any. Note that the
+ *         browser window might not be loaded yet - the function will return
+ *         |null| in such cases.
+ */
+BrowserTabList.prototype._getSelectedBrowser = function (window) {
+  return window.gBrowser ? window.gBrowser.selectedBrowser : null;
+};
+
+/**
+ * Produces an iterable (in this case a generator) to enumerate all available
+ * browser tabs.
+ */
+BrowserTabList.prototype._getBrowsers = function* () {
+  // Iterate over all navigator:browser XUL windows.
+  for (let win of allAppShellDOMWindows(DebuggerServer.chromeWindowType)) {
+    // For each tab in this XUL window, ensure that we have an actor for
+    // it, reusing existing actors where possible. We actually iterate
+    // over 'browser' XUL elements, and BrowserTabActor uses
+    // browser.contentWindow as the debuggee global.
+    for (let browser of this._getChildren(win)) {
+      yield browser;
+    }
+  }
+};
+
+BrowserTabList.prototype._getChildren = function (window) {
+  if (!window.gBrowser) {
+    return [];
+  }
+  let { gBrowser } = window;
+  if (!gBrowser.browsers) {
+    return [];
+  }
+  return gBrowser.browsers.filter(browser => {
+    // Filter tabs that are closing. listTabs calls made right after TabClose
+    // events still list tabs in process of being closed.
+    let tab = gBrowser.getTabForBrowser(browser);
+    return !tab.closing;
+  });
+};
+
+BrowserTabList.prototype.getList = function () {
+  let topXULWindow = Services.wm.getMostRecentWindow(
+    DebuggerServer.chromeWindowType);
+  let selectedBrowser = null;
+  if (topXULWindow) {
+    selectedBrowser = this._getSelectedBrowser(topXULWindow);
+  }
+
+  // As a sanity check, make sure all the actors presently in our map get
+  // picked up when we iterate over all windows' tabs.
+  let initialMapSize = this._actorByBrowser.size;
+  this._foundCount = 0;
+
+  // To avoid mysterious behavior if tabs are closed or opened mid-iteration,
+  // we update the map first, and then make a second pass over it to yield
+  // the actors. Thus, the sequence yielded is always a snapshot of the
+  // actors that were live when we began the iteration.
+
+  let actorPromises = [];
+
+  for (let browser of this._getBrowsers()) {
+    let selected = browser === selectedBrowser;
+    actorPromises.push(
+      this._getActorForBrowser(browser)
+          .then(actor => {
+            // Set the 'selected' properties on all actors correctly.
+            actor.selected = selected;
+            return actor;
+          })
+    );
+  }
+
+  if (this._testing && initialMapSize !== this._foundCount) {
+    throw new Error("_actorByBrowser map contained actors for dead tabs");
+  }
+
+  this._mustNotify = true;
+  this._checkListening();
+
+  return promise.all(actorPromises);
+};
+
+BrowserTabList.prototype._getActorForBrowser = function (browser) {
+  // Do we have an existing actor for this browser? If not, create one.
+  let actor = this._actorByBrowser.get(browser);
+  if (actor) {
+    this._foundCount++;
+    return actor.update();
+  }
+
+  actor = new BrowserTabActor(this._connection, browser);
+  this._actorByBrowser.set(browser, actor);
+  this._checkListening();
+  return actor.connect();
+};
+
+BrowserTabList.prototype.getTab = function ({ outerWindowID, tabId }) {
+  if (typeof outerWindowID == "number") {
+    // First look for in-process frames with this ID
+    let window = Services.wm.getOuterWindowWithId(outerWindowID);
+    // Safety check to prevent debugging top level window via getTab
+    if (window instanceof Ci.nsIDOMChromeWindow) {
+      return promise.reject({
+        error: "forbidden",
+        message: "Window with outerWindowID '" + outerWindowID + "' is chrome"
+      });
+    }
+    if (window) {
+      let iframe = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIDOMWindowUtils)
+                         .containerElement;
+      if (iframe) {
+        return this._getActorForBrowser(iframe);
+      }
+    }
+    // Then also look on registered <xul:browsers> when using outerWindowID for
+    // OOP tabs
+    for (let browser of this._getBrowsers()) {
+      if (browser.outerWindowID == outerWindowID) {
+        return this._getActorForBrowser(browser);
+      }
+    }
+    return promise.reject({
+      error: "noTab",
+      message: "Unable to find tab with outerWindowID '" + outerWindowID + "'"
+    });
+  } else if (typeof tabId == "number") {
+    // Tabs OOP
+    for (let browser of this._getBrowsers()) {
+      if (browser.frameLoader.tabParent &&
+          browser.frameLoader.tabParent.tabId === tabId) {
+        return this._getActorForBrowser(browser);
+      }
+    }
+    return promise.reject({
+      error: "noTab",
+      message: "Unable to find tab with tabId '" + tabId + "'"
+    });
+  }
+
+  let topXULWindow = Services.wm.getMostRecentWindow(
+    DebuggerServer.chromeWindowType);
+  if (topXULWindow) {
+    let selectedBrowser = this._getSelectedBrowser(topXULWindow);
+    return this._getActorForBrowser(selectedBrowser);
+  }
+  return promise.reject({
+    error: "noTab",
+    message: "Unable to find any selected browser"
+  });
+};
+
+Object.defineProperty(BrowserTabList.prototype, "onListChanged", {
+  enumerable: true,
+  configurable: true,
+  get() {
+    return this._onListChanged;
+  },
+  set(v) {
+    if (v !== null && typeof v !== "function") {
+      throw new Error(
+        "onListChanged property may only be set to 'null' or a function");
+    }
+    this._onListChanged = v;
+    this._checkListening();
+  }
+});
+
+/**
+ * The set of tabs has changed somehow. Call our onListChanged handler, if
+ * one is set, and if we haven't already called it since the last iteration.
+ */
+BrowserTabList.prototype._notifyListChanged = function () {
+  if (!this._onListChanged) {
+    return;
+  }
+  if (this._mustNotify) {
+    this._onListChanged();
+    this._mustNotify = false;
+  }
+};
+
+/**
+ * Exit |actor|, belonging to |browser|, and notify the onListChanged
+ * handle if needed.
+ */
+BrowserTabList.prototype._handleActorClose = function (actor, browser) {
+  if (this._testing) {
+    if (this._actorByBrowser.get(browser) !== actor) {
+      throw new Error("BrowserTabActor not stored in map under given browser");
+    }
+    if (actor.browser !== browser) {
+      throw new Error("actor's browser and map key don't match");
+    }
+  }
+
+  this._actorByBrowser.delete(browser);
+  actor.exit();
+
+  this._notifyListChanged();
+  this._checkListening();
+};
+
+/**
+ * Make sure we are listening or not listening for activity elsewhere in
+ * the browser, as appropriate. Other than setting up newly created XUL
+ * windows, all listener / observer connection and disconnection should
+ * happen here.
+ */
+BrowserTabList.prototype._checkListening = function () {
+  /*
+   * If we have an onListChanged handler that we haven't sent an announcement
+   * to since the last iteration, we need to watch for tab creation as well as
+   * change of the currently selected tab and tab title changes of tabs in
+   * parent process via TabAttrModified (tabs oop uses DOMTitleChanges).
+   *
+   * Oddly, we don't need to watch for 'close' events here. If our actor list
+   * is empty, then either it was empty the last time we iterated, and no
+   * close events are possible, or it was not empty the last time we
+   * iterated, but all the actors have since been closed, and we must have
+   * sent a notification already when they closed.
+   */
+  this._listenForEventsIf(this._onListChanged && this._mustNotify,
+                          "_listeningForTabOpen",
+                          ["TabOpen", "TabSelect", "TabAttrModified"]);
+
+  /* If we have live actors, we need to be ready to mark them dead. */
+  this._listenForEventsIf(this._actorByBrowser.size > 0,
+                          "_listeningForTabClose",
+                          ["TabClose", "TabRemotenessChange"]);
+
+  /*
+   * We must listen to the window mediator in either case, since that's the
+   * only way to find out about tabs that come and go when top-level windows
+   * are opened and closed.
+   */
+  this._listenToMediatorIf((this._onListChanged && this._mustNotify) ||
+                           (this._actorByBrowser.size > 0));
+
+  /*
+   * We also listen for title changed from the child process.
+   * This allows listening for title changes from Fennec and OOP tabs in Fx.
+   */
+  this._listenForMessagesIf(this._onListChanged && this._mustNotify,
+                            "_listeningForTitleChange",
+                            ["DOMTitleChanged"]);
+};
+
+/*
+ * Add or remove event listeners for all XUL windows.
+ *
+ * @param shouldListen boolean
+ *    True if we should add event handlers; false if we should remove them.
+ * @param guard string
+ *    The name of a guard property of 'this', indicating whether we're
+ *    already listening for those events.
+ * @param eventNames array of strings
+ *    An array of event names.
+ */
+BrowserTabList.prototype._listenForEventsIf =
+  function (shouldListen, guard, eventNames) {
+    if (!shouldListen !== !this[guard]) {
+      let op = shouldListen ? "addEventListener" : "removeEventListener";
+      for (let win of allAppShellDOMWindows(DebuggerServer.chromeWindowType)) {
+        for (let name of eventNames) {
+          win[op](name, this, false);
+        }
+      }
+      this[guard] = shouldListen;
+    }
+  };
+
+/*
+ * Add or remove message listeners for all XUL windows.
+ *
+ * @param aShouldListen boolean
+ *    True if we should add message listeners; false if we should remove them.
+ * @param aGuard string
+ *    The name of a guard property of 'this', indicating whether we're
+ *    already listening for those messages.
+ * @param aMessageNames array of strings
+ *    An array of message names.
+ */
+BrowserTabList.prototype._listenForMessagesIf =
+  function (shouldListen, guard, messageNames) {
+    if (!shouldListen !== !this[guard]) {
+      let op = shouldListen ? "addMessageListener" : "removeMessageListener";
+      for (let win of allAppShellDOMWindows(DebuggerServer.chromeWindowType)) {
+        for (let name of messageNames) {
+          win.messageManager[op](name, this);
+        }
+      }
+      this[guard] = shouldListen;
+    }
+  };
+
+/**
+ * Implement nsIMessageListener.
+ */
+BrowserTabList.prototype.receiveMessage = DevToolsUtils.makeInfallible(
+  function (message) {
+    let browser = message.target;
+    switch (message.name) {
+      case "DOMTitleChanged": {
+        let actor = this._actorByBrowser.get(browser);
+        if (actor) {
+          this._notifyListChanged();
+          this._checkListening();
+        }
+        break;
+      }
+    }
+  });
+
+/**
+ * Implement nsIDOMEventListener.
+ */
+BrowserTabList.prototype.handleEvent =
+DevToolsUtils.makeInfallible(function (event) {
+  let browser = event.target.linkedBrowser;
+  switch (event.type) {
+    case "TabOpen":
+    case "TabSelect": {
+      /* Don't create a new actor; iterate will take care of that. Just notify. */
+      this._notifyListChanged();
+      this._checkListening();
+      break;
+    }
+    case "TabClose": {
+      let actor = this._actorByBrowser.get(browser);
+      if (actor) {
+        this._handleActorClose(actor, browser);
+      }
+      break;
+    }
+    case "TabRemotenessChange": {
+      // We have to remove the cached actor as we have to create a new instance.
+      let actor = this._actorByBrowser.get(browser);
+      if (actor) {
+        this._actorByBrowser.delete(browser);
+        // Don't create a new actor; iterate will take care of that. Just notify.
+        this._notifyListChanged();
+        this._checkListening();
+      }
+      break;
+    }
+    case "TabAttrModified": {
+      // Remote <browser> title changes are handled via DOMTitleChange message
+      // TabAttrModified is only here for browsers in parent process which
+      // don't send this message.
+      if (browser.isRemoteBrowser) {
+        break;
+      }
+      let actor = this._actorByBrowser.get(browser);
+      if (actor) {
+        // TabAttrModified is fired in various cases, here only care about title
+        // changes
+        if (event.detail.changed.includes("label")) {
+          this._notifyListChanged();
+          this._checkListening();
+        }
+      }
+      break;
+    }
+  }
+}, "BrowserTabList.prototype.handleEvent");
+
+/*
+ * If |shouldListen| is true, ensure we've registered a listener with the
+ * window mediator. Otherwise, ensure we haven't registered a listener.
+ */
+BrowserTabList.prototype._listenToMediatorIf = function (shouldListen) {
+  if (!shouldListen !== !this._listeningToMediator) {
+    let op = shouldListen ? "addListener" : "removeListener";
+    Services.wm[op](this);
+    this._listeningToMediator = shouldListen;
+  }
+};
+
+/**
+ * nsIWindowMediatorListener implementation.
+ *
+ * See _onTabClosed for explanation of why we needn't actually tweak any
+ * actors or tables here.
+ *
+ * An nsIWindowMediatorListener's methods get passed all sorts of windows; we
+ * only care about the tab containers. Those have 'getBrowser' methods.
+ */
+BrowserTabList.prototype.onWindowTitleChange = () => { };
+
+BrowserTabList.prototype.onOpenWindow =
+DevToolsUtils.makeInfallible(function (window) {
+  let handleLoad = DevToolsUtils.makeInfallible(() => {
+    /* We don't want any further load events from this window. */
+    window.removeEventListener("load", handleLoad, false);
+
+    if (appShellDOMWindowType(window) !== DebuggerServer.chromeWindowType) {
+      return;
+    }
+
+    // Listen for future tab activity.
+    if (this._listeningForTabOpen) {
+      window.addEventListener("TabOpen", this, false);
+      window.addEventListener("TabSelect", this, false);
+      window.addEventListener("TabAttrModified", this, false);
+    }
+    if (this._listeningForTabClose) {
+      window.addEventListener("TabClose", this, false);
+      window.addEventListener("TabRemotenessChange", this, false);
+    }
+    if (this._listeningForTitleChange) {
+      window.messageManager.addMessageListener("DOMTitleChanged", this);
+    }
+
+    // As explained above, we will not receive a TabOpen event for this
+    // document's initial tab, so we must notify our client of the new tab
+    // this will have.
+    this._notifyListChanged();
+  });
+
+  /*
+   * You can hardly do anything at all with a XUL window at this point; it
+   * doesn't even have its document yet. Wait until its document has
+   * loaded, and then see what we've got. This also avoids
+   * nsIWindowMediator enumeration from within listeners (bug 873589).
+   */
+  window = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                 .getInterface(Ci.nsIDOMWindow);
+
+  window.addEventListener("load", handleLoad, false);
+}, "BrowserTabList.prototype.onOpenWindow");
+
+BrowserTabList.prototype.onCloseWindow =
+DevToolsUtils.makeInfallible(function (window) {
+  window = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                   .getInterface(Ci.nsIDOMWindow);
+
+  if (appShellDOMWindowType(window) !== DebuggerServer.chromeWindowType) {
+    return;
+  }
+
+  /*
+   * nsIWindowMediator deadlocks if you call its GetEnumerator method from
+   * a nsIWindowMediatorListener's onCloseWindow hook (bug 873589), so
+   * handle the close in a different tick.
+   */
+  Services.tm.currentThread.dispatch(DevToolsUtils.makeInfallible(() => {
+    /*
+     * Scan the entire map for actors representing tabs that were in this
+     * top-level window, and exit them.
+     */
+    for (let [browser, actor] of this._actorByBrowser) {
+      /* The browser document of a closed window has no default view. */
+      if (!browser.ownerDocument.defaultView) {
+        this._handleActorClose(actor, browser);
+      }
+    }
+  }, "BrowserTabList.prototype.onCloseWindow's delayed body"), 0);
+}, "BrowserTabList.prototype.onCloseWindow");
+
+exports.BrowserTabList = BrowserTabList;
+
+/**
+ * Creates a TabActor whose main goal is to manage lifetime and
+ * expose the tab actors being registered via DebuggerServer.registerModule.
+ * But also track the lifetime of the document being tracked.
+ *
+ * ### Main requests:
+ *
+ * `attach`/`detach` requests:
+ *  - start/stop document watching:
+ *    Starts watching for new documents and emits `tabNavigated` and
+ *    `frameUpdate` over RDP.
+ *  - retrieve the thread actor:
+ *    Instantiates a ThreadActor that can be later attached to in order to
+ *    debug JS sources in the document.
+ * `switchToFrame`:
+ *  Change the targeted document of the whole TabActor, and its child tab actors
+ *  to an iframe or back to its original document.
+ *
+ * Most of the TabActor properties (like `chromeEventHandler` or `docShells`)
+ * are meant to be used by the various child tab actors.
+ *
+ * ### RDP events:
+ *
+ *  - `tabNavigated`:
+ *    Sent when the tab is about to navigate or has just navigated to
+ *    a different document.
+ *    This event contains the following attributes:
+ *     * url (string) The new URI being loaded.
+ *     * nativeConsoleAPI (boolean) `false` if the console API of the page has
+ *                                          been overridden (e.g. by Firebug),
+ *                                  `true`  if the Gecko implementation is used.
+ *     * state (string) `start` if we just start requesting the new URL,
+ *                      `stop`  if the new URL is done loading.
+ *     * isFrameSwitching (boolean) Indicates the event is dispatched when
+ *                                  switching the TabActor context to
+ *                                  a different frame. When we switch to
+ *                                  an iframe, there is no document load.
+ *                                  The targeted document is most likely
+ *                                  going to be already done loading.
+ *     * title (string) The document title being loaded.
+ *                      (sent only on state=stop)
+ *
+ *  - `frameUpdate`:
+ *    Sent when there was a change in the child frames contained in the document
+ *    or when the tab's context was switched to another frame.
+ *    This event can have four different forms depending on the type of change:
+ *    * One or many frames are updated:
+ *      { frames: [{ id, url, title, parentID }, ...] }
+ *    * One frame got destroyed:
+ *      { frames: [{ id, destroy: true }]}
+ *    * All frames got destroyed:
+ *      { destroyAll: true }
+ *    * We switched the context of the TabActor to a specific frame:
+ *      { selected: #id }
+ *
+ * ### Internal, non-rdp events:
+ * Various events are also dispatched on the TabActor itself that are not
+ * related to RDP, so, not sent to the client. They all relate to the documents
+ * tracked by the TabActor (its main targeted document, but also any of its
+ * iframes).
+ *  - will-navigate
+ *    This event fires once navigation starts.
+ *    All pending user prompts are dealt with,
+ *    but it is fired before the first request starts.
+ *  - navigate
+ *    This event is fired once the document's readyState is "complete".
+ *  - window-ready
+ *    This event is fired on three distinct scenarios:
+ *     * When a new Window object is crafted, equivalent of `DOMWindowCreated`.
+ *       It is dispatched before any page script is executed.
+ *     * We will have already received a window-ready event for this window
+ *       when it was created, but we received a window-destroyed event when
+ *       it was frozen into the bfcache, and now the user navigated back to
+ *       this page, so it's now live again and we should resume handling it.
+ *     * For each existing document, when an `attach` request is received.
+ *       At this point scripts in the page will be already loaded.
+ *  - window-destroyed
+ *    This event is fired in two cases:
+ *     * When the window object is destroyed, i.e. when the related document
+ *       is garbage collected. This can happen when the tab is closed or the
+ *       iframe is removed from the DOM.
+ *       It is equivalent of `inner-window-destroyed` event.
+ *     * When the page goes into the bfcache and gets frozen.
+ *       The equivalent of `pagehide`.
+ *  - changed-toplevel-document
+ *    This event fires when we switch the TabActor targeted document
+ *    to one of its iframes, or back to its original top document.
+ *    It is dispatched between window-destroyed and window-ready.
+ *  - stylesheet-added
+ *    This event is fired when a StyleSheetActor is created.
+ *    It contains the following attribute :
+ *     * actor (StyleSheetActor) The created actor.
+ *
+ * Note that *all* these events are dispatched in the following order
+ * when we switch the context of the TabActor to a given iframe:
+ *  - will-navigate
+ *  - window-destroyed
+ *  - changed-toplevel-document
+ *  - window-ready
+ *  - navigate
+ *
+ * This class is subclassed by ContentActor and others.
+ * Subclasses are expected to implement a getter for the docShell property.
+ *
+ * @param connection DebuggerServerConnection
+ *        The conection to the client.
+ */
+function TabActor(connection) {
+  this.conn = connection;
+  this._tabActorPool = null;
+  // A map of actor names to actor instances provided by extensions.
+  this._extraActors = {};
+  this._exited = false;
+  this._sources = null;
+
+  // Map of DOM stylesheets to StyleSheetActors
+  this._styleSheetActors = new Map();
+
+  this._shouldAddNewGlobalAsDebuggee =
+    this._shouldAddNewGlobalAsDebuggee.bind(this);
+
+  this.makeDebugger = makeDebugger.bind(null, {
+    findDebuggees: () => {
+      return this.windows.concat(this.webextensionsContentScriptGlobals);
+    },
+    shouldAddNewGlobalAsDebuggee: this._shouldAddNewGlobalAsDebuggee
+  });
+
+  // Flag eventually overloaded by sub classes in order to watch new docshells
+  // Used by the ChromeActor to list all frames in the Browser Toolbox
+  this.listenForNewDocShells = false;
+
+  this.traits = {
+    reconfigure: true,
+    // Supports frame listing via `listFrames` request and `frameUpdate` events
+    // as well as frame switching via `switchToFrame` request
+    frames: true,
+    // Do not require to send reconfigure request to reset the document state
+    // to what it was before using the TabActor
+    noTabReconfigureOnClose: true
+  };
+
+  this._workerActorList = null;
+  this._workerActorPool = null;
+  this._onWorkerActorListChanged = this._onWorkerActorListChanged.bind(this);
+}
+
+// XXX (bug 710213): TabActor attach/detach/exit/disconnect is a
+// *complete* mess, needs to be rethought asap.
+
+TabActor.prototype = {
+  traits: null,
+
+  // Optional console API listener options (e.g. used by the WebExtensionActor to
+  // filter console messages by addonID), set to an empty (no options) object by default.
+  consoleAPIListenerOptions: {},
+
+  // Optional TabSources filter function (e.g. used by the WebExtensionActor to filter
+  // sources by addonID), allow all sources by default.
+  _allowSource() {
+    return true;
+  },
+
+  get exited() {
+    return this._exited;
+  },
+
+  get attached() {
+    return !!this._attached;
+  },
+
+  _tabPool: null,
+  get tabActorPool() {
+    return this._tabPool;
+  },
+
+  _contextPool: null,
+  get contextActorPool() {
+    return this._contextPool;
+  },
+
+  // A constant prefix that will be used to form the actor ID by the server.
+  actorPrefix: "tab",
+
+  /**
+   * An object on which listen for DOMWindowCreated and pageshow events.
+   */
+  get chromeEventHandler() {
+    return getDocShellChromeEventHandler(this.docShell);
+  },
+
+  /**
+   * Getter for the nsIMessageManager associated to the tab.
+   */
+  get messageManager() {
+    try {
+      return this.docShell
+        .QueryInterface(Ci.nsIInterfaceRequestor)
+        .getInterface(Ci.nsIContentFrameMessageManager);
+    } catch (e) {
+      return null;
+    }
+  },
+
+  /**
+   * Getter for the tab's doc shell.
+   */
+  get docShell() {
+    throw new Error(
+      "The docShell getter should be implemented by a subclass of TabActor");
+  },
+
+  /**
+   * Getter for the list of all docshell in this tabActor
+   * @return {Array}
+   */
+  get docShells() {
+    return getChildDocShells(this.docShell);
+  },
+
+  /**
+   * Getter for the tab content's DOM window.
+   */
+  get window() {
+    // On xpcshell, there is no document
+    if (this.docShell) {
+      return this.docShell
+        .QueryInterface(Ci.nsIInterfaceRequestor)
+        .getInterface(Ci.nsIDOMWindow);
+    }
+    return null;
+  },
+
+  get outerWindowID() {
+    if (this.window) {
+      return this.window.QueryInterface(Ci.nsIInterfaceRequestor)
+                        .getInterface(Ci.nsIDOMWindowUtils)
+                        .outerWindowID;
+    }
+    return null;
+  },
+
+  /**
+   * Getter for the WebExtensions ContentScript globals related to the
+   * current tab content's DOM window.
+   */
+  get webextensionsContentScriptGlobals() {
+    // Ignore xpcshell runtime which spawn TabActors without a window.
+    if (this.window) {
+      return ExtensionContent.getContentScriptGlobalsForWindow(this.window);
+    }
+
+    return [];
+  },
+
+  /**
+   * Getter for the list of all content DOM windows in this tabActor
+   * @return {Array}
+   */
+  get windows() {
+    return this.docShells.map(docShell => {
+      return docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                     .getInterface(Ci.nsIDOMWindow);
+    });
+  },
+
+  /**
+   * Getter for the original docShell the tabActor got attached to in the first
+   * place.
+   * Note that your actor should normally *not* rely on this top level docShell
+   * if you want it to show information relative to the iframe that's currently
+   * being inspected in the toolbox.
+   */
+  get originalDocShell() {
+    if (!this._originalWindow) {
+      return this.docShell;
+    }
+
+    return this._originalWindow.QueryInterface(Ci.nsIInterfaceRequestor)
+                               .getInterface(Ci.nsIWebNavigation)
+                               .QueryInterface(Ci.nsIDocShell);
+  },
+
+  /**
+   * Getter for the original window the tabActor got attached to in the first
+   * place.
+   * Note that your actor should normally *not* rely on this top level window if
+   * you want it to show information relative to the iframe that's currently
+   * being inspected in the toolbox.
+   */
+  get originalWindow() {
+    return this._originalWindow || this.window;
+  },
+
+  /**
+   * Getter for the nsIWebProgress for watching this window.
+   */
+  get webProgress() {
+    return this.docShell
+      .QueryInterface(Ci.nsIInterfaceRequestor)
+      .getInterface(Ci.nsIWebProgress);
+  },
+
+  /**
+   * Getter for the nsIWebNavigation for the tab.
+   */
+  get webNavigation() {
+    return this.docShell
+      .QueryInterface(Ci.nsIInterfaceRequestor)
+      .getInterface(Ci.nsIWebNavigation);
+  },
+
+  /**
+   * Getter for the tab's document.
+   */
+  get contentDocument() {
+    return this.webNavigation.document;
+  },
+
+  /**
+   * Getter for the tab title.
+   * @return string
+   *         Tab title.
+   */
+  get title() {
+    return this.contentDocument.contentTitle;
+  },
+
+  /**
+   * Getter for the tab URL.
+   * @return string
+   *         Tab URL.
+   */
+  get url() {
+    if (this.webNavigation.currentURI) {
+      return this.webNavigation.currentURI.spec;
+    }
+    // Abrupt closing of the browser window may leave callbacks without a
+    // currentURI.
+    return null;
+  },
+
+  get sources() {
+    if (!this._sources) {
+      this._sources = new TabSources(this.threadActor, this._allowSource);
+    }
+    return this._sources;
+  },
+
+  /**
+   * This is called by BrowserTabList.getList for existing tab actors prior to
+   * calling |form| below.  It can be used to do any async work that may be
+   * needed to assemble the form.
+   */
+  update() {
+    return promise.resolve(this);
+  },
+
+  form() {
+    assert(!this.exited,
+               "form() shouldn't be called on exited browser actor.");
+    assert(this.actorID,
+               "tab should have an actorID.");
+
+    let response = {
+      actor: this.actorID
+    };
+
+    // We may try to access window while the document is closing, then
+    // accessing window throws. Also on xpcshell we are using tabactor even if
+    // there is no valid document.
+    if (this.docShell && !this.docShell.isBeingDestroyed()) {
+      response.title = this.title;
+      response.url = this.url;
+      response.outerWindowID = this.outerWindowID;
+    }
+
+    // Always use the same ActorPool, so existing actor instances
+    // (created in createExtraActors) are not lost.
+    if (!this._tabActorPool) {
+      this._tabActorPool = new ActorPool(this.conn);
+      this.conn.addActorPool(this._tabActorPool);
+    }
+
+    // Walk over tab actor factories and make sure they are all
+    // instantiated and added into the ActorPool. Note that some
+    // factories can be added dynamically by extensions.
+    this._createExtraActors(DebuggerServer.tabActorFactories,
+      this._tabActorPool);
+
+    this._appendExtraActors(response);
+    return response;
+  },
+
+  /**
+   * Called when the actor is removed from the connection.
+   */
+  disconnect() {
+    this.exit();
+  },
+
+  /**
+   * Called by the root actor when the underlying tab is closed.
+   */
+  exit() {
+    if (this.exited) {
+      return;
+    }
+
+    // Tell the thread actor that the tab is closed, so that it may terminate
+    // instead of resuming the debuggee script.
+    if (this._attached) {
+      this.threadActor._tabClosed = true;
+    }
+
+    this._detach();
+
+    Object.defineProperty(this, "docShell", {
+      value: null,
+      configurable: true
+    });
+
+    this._extraActors = null;
+
+    this._exited = true;
+  },
+
+  /**
+   * Return true if the given global is associated with this tab and should be
+   * added as a debuggee, false otherwise.
+   */
+  _shouldAddNewGlobalAsDebuggee(wrappedGlobal) {
+    if (wrappedGlobal.hostAnnotations &&
+        wrappedGlobal.hostAnnotations.type == "document" &&
+        wrappedGlobal.hostAnnotations.element === this.window) {
+      return true;
+    }
+
+    let global = unwrapDebuggerObjectGlobal(wrappedGlobal);
+    if (!global) {
+      return false;
+    }
+
+    // Check if the global is a sdk page-mod sandbox.
+    let metadata = {};
+    let id = "";
+    try {
+      id = getInnerId(this.window);
+      metadata = Cu.getSandboxMetadata(global);
+    } catch (e) {
+      // ignore
+    }
+    if (metadata
+        && metadata["inner-window-id"]
+        && metadata["inner-window-id"] == id) {
+      return true;
+    }
+
+    return false;
+  },
+
+  /* Support for DebuggerServer.addTabActor. */
+  _createExtraActors: createExtraActors,
+  _appendExtraActors: appendExtraActors,
+
+  /**
+   * Does the actual work of attaching to a tab.
+   */
+  _attach() {
+    if (this._attached) {
+      return;
+    }
+
+    // Create a pool for tab-lifetime actors.
+    assert(!this._tabPool, "Shouldn't have a tab pool if we weren't attached.");
+    this._tabPool = new ActorPool(this.conn);
+    this.conn.addActorPool(this._tabPool);
+
+    // ... and a pool for context-lifetime actors.
+    this._pushContext();
+
+    // on xpcshell, there is no document
+    if (this.window) {
+      this._progressListener = new DebuggerProgressListener(this);
+
+      // Save references to the original document we attached to
+      this._originalWindow = this.window;
+
+      // Ensure replying to attach() request first
+      // before notifying about new docshells.
+      DevToolsUtils.executeSoon(() => this._watchDocshells());
+    }
+
+    this._attached = true;
+  },
+
+  _watchDocshells() {
+    // In child processes, we watch all docshells living in the process.
+    if (this.listenForNewDocShells) {
+      Services.obs.addObserver(this, "webnavigation-create", false);
+    }
+    Services.obs.addObserver(this, "webnavigation-destroy", false);
+
+    // We watch for all child docshells under the current document,
+    this._progressListener.watch(this.docShell);
+
+    // And list all already existing ones.
+    this._updateChildDocShells();
+  },
+
+  onSwitchToFrame(request) {
+    let windowId = request.windowId;
+    let win;
+
+    try {
+      win = Services.wm.getOuterWindowWithId(windowId);
+    } catch (e) {
+      // ignore
+    }
+    if (!win) {
+      return { error: "noWindow",
+               message: "The related docshell is destroyed or not found" };
+    } else if (win == this.window) {
+      return {};
+    }
+
+    // Reply first before changing the document
+    DevToolsUtils.executeSoon(() => this._changeTopLevelDocument(win));
+
+    return {};
+  },
+
+  onListFrames(request) {
+    let windows = this._docShellsToWindows(this.docShells);
+    return { frames: windows };
+  },
+
+  onListWorkers(request) {
+    if (!this.attached) {
+      return { error: "wrongState" };
+    }
+
+    if (this._workerActorList === null) {
+      this._workerActorList = new WorkerActorList(this.conn, {
+        type: Ci.nsIWorkerDebugger.TYPE_DEDICATED,
+        window: this.window
+      });
+    }
+
+    return this._workerActorList.getList().then((actors) => {
+      let pool = new ActorPool(this.conn);
+      for (let actor of actors) {
+        pool.addActor(actor);
+      }
+
+      this.conn.removeActorPool(this._workerActorPool);
+      this._workerActorPool = pool;
+      this.conn.addActorPool(this._workerActorPool);
+
+      this._workerActorList.onListChanged = this._onWorkerActorListChanged;
+
+      return {
+        "from": this.actorID,
+        "workers": actors.map((actor) => actor.form())
+      };
+    });
+  },
+
+  _onWorkerActorListChanged() {
+    this._workerActorList.onListChanged = null;
+    this.conn.sendActorEvent(this.actorID, "workerListChanged");
+  },
+
+  observe(subject, topic, data) {
+    // Ignore any event that comes before/after the tab actor is attached
+    // That typically happens during firefox shutdown.
+    if (!this.attached) {
+      return;
+    }
+    if (topic == "webnavigation-create") {
+      subject.QueryInterface(Ci.nsIDocShell);
+      this._onDocShellCreated(subject);
+    } else if (topic == "webnavigation-destroy") {
+      this._onDocShellDestroy(subject);
+    }
+  },
+
+  _onDocShellCreated(docShell) {
+    // (chrome-)webnavigation-create is fired very early during docshell
+    // construction. In new root docshells within child processes, involving
+    // TabChild, this event is from within this call:
+    //   http://hg.mozilla.org/mozilla-central/annotate/74d7fb43bb44/dom/ipc/TabChild.cpp#l912
+    // whereas the chromeEventHandler (and most likely other stuff) is set
+    // later:
+    //   http://hg.mozilla.org/mozilla-central/annotate/74d7fb43bb44/dom/ipc/TabChild.cpp#l944
+    // So wait a tick before watching it:
+    DevToolsUtils.executeSoon(() => {
+      // Bug 1142752: sometimes, the docshell appears to be immediately
+      // destroyed, bailout early to prevent random exceptions.
+      if (docShell.isBeingDestroyed()) {
+        return;
+      }
+
+      // In child processes, we have new root docshells,
+      // let's watch them and all their child docshells.
+      if (this._isRootDocShell(docShell)) {
+        this._progressListener.watch(docShell);
+      }
+      this._notifyDocShellsUpdate([docShell]);
+    });
+  },
+
+  _onDocShellDestroy(docShell) {
+    let webProgress = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                              .getInterface(Ci.nsIWebProgress);
+    this._notifyDocShellDestroy(webProgress);
+  },
+
+  _isRootDocShell(docShell) {
+    // Should report as root docshell:
+    //  - New top level window's docshells, when using ChromeActor against a
+    // process. It allows tracking iframes of the newly opened windows
+    // like Browser console or new browser windows.
+    //  - MozActivities or window.open frames on B2G, where a new root docshell
+    // is spawn in the child process of the app.
+    return !docShell.parent;
+  },
+
+  // Convert docShell list to windows objects list being sent to the client
+  _docShellsToWindows(docshells) {
+    return docshells.map(docShell => {
+      let webProgress = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                                .getInterface(Ci.nsIWebProgress);
+      let window = webProgress.DOMWindow;
+      let id = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                     .getInterface(Ci.nsIDOMWindowUtils)
+                     .outerWindowID;
+      let parentID = undefined;
+      // Ignore the parent of the original document on non-e10s firefox,
+      // as we get the xul window as parent and don't care about it.
+      if (window.parent && window != this._originalWindow) {
+        parentID = window.parent
+                         .QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIDOMWindowUtils)
+                         .outerWindowID;
+      }
+
+      // Collect the addonID from the document origin attributes.
+      let addonID = window.document.nodePrincipal.originAttributes.addonId;
+
+      return {
+        id,
+        parentID,
+        addonID,
+        url: window.location.href,
+        title: window.document.title,
+      };
+    });
+  },
+
+  _notifyDocShellsUpdate(docshells) {
+    let windows = this._docShellsToWindows(docshells);
+
+    // Do not send the `frameUpdate` event if the windows array is empty.
+    if (windows.length == 0) {
+      return;
+    }
+
+    this.conn.send({
+      from: this.actorID,
+      type: "frameUpdate",
+      frames: windows
+    });
+  },
+
+  _updateChildDocShells() {
+    this._notifyDocShellsUpdate(this.docShells);
+  },
+
+  _notifyDocShellDestroy(webProgress) {
+    webProgress = webProgress.QueryInterface(Ci.nsIWebProgress);
+    let id = webProgress.DOMWindow
+                        .QueryInterface(Ci.nsIInterfaceRequestor)
+                        .getInterface(Ci.nsIDOMWindowUtils)
+                        .outerWindowID;
+    this.conn.send({
+      from: this.actorID,
+      type: "frameUpdate",
+      frames: [{
+        id,
+        destroy: true
+      }]
+    });
+
+    // Stop watching this docshell (the unwatch() method will check if we
+    // started watching it before).
+    webProgress.QueryInterface(Ci.nsIDocShell);
+    this._progressListener.unwatch(webProgress);
+
+    if (webProgress.DOMWindow == this._originalWindow) {
+      // If the original top level document we connected to is removed,
+      // we try to switch to any other top level document
+      let rootDocShells = this.docShells
+                              .filter(d => {
+                                return d != this.docShell &&
+                                       this._isRootDocShell(d);
+                              });
+      if (rootDocShells.length > 0) {
+        let newRoot = rootDocShells[0];
+        this._originalWindow = newRoot.DOMWindow;
+        this._changeTopLevelDocument(this._originalWindow);
+      } else {
+        // If for some reason (typically during Firefox shutdown), the original
+        // document is destroyed, and there is no other top level docshell,
+        // we detach the tab actor to unregister all listeners and prevent any
+        // exception
+        this.exit();
+      }
+      return;
+    }
+
+    // If the currently targeted context is destroyed,
+    // and we aren't on the top-level document,
+    // we have to switch to the top-level one.
+    if (webProgress.DOMWindow == this.window &&
+        this.window != this._originalWindow) {
+      this._changeTopLevelDocument(this._originalWindow);
+    }
+  },
+
+  _notifyDocShellDestroyAll() {
+    this.conn.send({
+      from: this.actorID,
+      type: "frameUpdate",
+      destroyAll: true
+    });
+  },
+
+  /**
+   * Creates a thread actor and a pool for context-lifetime actors. It then sets
+   * up the content window for debugging.
+   */
+  _pushContext() {
+    assert(!this._contextPool, "Can't push multiple contexts");
+
+    this._contextPool = new ActorPool(this.conn);
+    this.conn.addActorPool(this._contextPool);
+
+    this.threadActor = new ThreadActor(this, this.window);
+    this._contextPool.addActor(this.threadActor);
+  },
+
+  /**
+   * Exits the current thread actor and removes the context-lifetime actor pool.
+   * The content window is no longer being debugged after this call.
+   */
+  _popContext() {
+    assert(!!this._contextPool, "No context to pop.");
+
+    this.conn.removeActorPool(this._contextPool);
+    this._contextPool = null;
+    this.threadActor.exit();
+    this.threadActor = null;
+    this._sources = null;
+  },
+
+  /**
+   * Does the actual work of detaching from a tab.
+   *
+   * @returns false if the tab wasn't attached or true of detaching succeeds.
+   */
+  _detach() {
+    if (!this.attached) {
+      return false;
+    }
+
+    // Check for docShell availability, as it can be already gone
+    // during Firefox shutdown.
+    if (this.docShell) {
+      this._progressListener.unwatch(this.docShell);
+      this._restoreDocumentSettings();
+    }
+    if (this._progressListener) {
+      this._progressListener.destroy();
+      this._progressListener = null;
+      this._originalWindow = null;
+
+      // Removes the observers being set in _watchDocShells
+      if (this.listenForNewDocShells) {
+        Services.obs.removeObserver(this, "webnavigation-create");
+      }
+      Services.obs.removeObserver(this, "webnavigation-destroy");
+    }
+
+    this._popContext();
+
+    // Shut down actors that belong to this tab's pool.
+    for (let sheetActor of this._styleSheetActors.values()) {
+      this._tabPool.removeActor(sheetActor);
+    }
+    this._styleSheetActors.clear();
+    this.conn.removeActorPool(this._tabPool);
+    this._tabPool = null;
+    if (this._tabActorPool) {
+      this.conn.removeActorPool(this._tabActorPool);
+      this._tabActorPool = null;
+    }
+
+    // Make sure that no more workerListChanged notifications are sent.
+    if (this._workerActorList !== null) {
+      this._workerActorList.onListChanged = null;
+      this._workerActorList = null;
+    }
+
+    if (this._workerActorPool !== null) {
+      this.conn.removeActorPool(this._workerActorPool);
+      this._workerActorPool = null;
+    }
+
+    this._attached = false;
+
+    this.conn.send({ from: this.actorID,
+                     type: "tabDetached" });
+
+    return true;
+  },
+
+  // Protocol Request Handlers
+
+  onAttach(request) {
+    if (this.exited) {
+      return { type: "exited" };
+    }
+
+    this._attach();
+
+    return {
+      type: "tabAttached",
+      threadActor: this.threadActor.actorID,
+      cacheDisabled: this._getCacheDisabled(),
+      javascriptEnabled: this._getJavascriptEnabled(),
+      traits: this.traits,
+    };
+  },
+
+  onDetach(request) {
+    if (!this._detach()) {
+      return { error: "wrongState" };
+    }
+
+    return { type: "detached" };
+  },
+
+  /**
+   * Bring the tab's window to front.
+   */
+  onFocus() {
+    if (this.window) {
+      this.window.focus();
+    }
+    return {};
+  },
+
+  /**
+   * Reload the page in this tab.
+   */
+  onReload(request) {
+    let force = request && request.options && request.options.force;
+    // Wait a tick so that the response packet can be dispatched before the
+    // subsequent navigation event packet.
+    Services.tm.currentThread.dispatch(DevToolsUtils.makeInfallible(() => {
+      // This won't work while the browser is shutting down and we don't really
+      // care.
+      if (Services.startup.shuttingDown) {
+        return;
+      }
+      this.webNavigation.reload(force ?
+        Ci.nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE :
+        Ci.nsIWebNavigation.LOAD_FLAGS_NONE);
+    }, "TabActor.prototype.onReload's delayed body"), 0);
+    return {};
+  },
+
+  /**
+   * Navigate this tab to a new location
+   */
+  onNavigateTo(request) {
+    // Wait a tick so that the response packet can be dispatched before the
+    // subsequent navigation event packet.
+    Services.tm.currentThread.dispatch(DevToolsUtils.makeInfallible(() => {
+      this.window.location = request.url;
+    }, "TabActor.prototype.onNavigateTo's delayed body"), 0);
+    return {};
+  },
+
+  /**
+   * Reconfigure options.
+   */
+  onReconfigure(request) {
+    let options = request.options || {};
+
+    if (!this.docShell) {
+      // The tab is already closed.
+      return {};
+    }
+    this._toggleDevToolsSettings(options);
+
+    return {};
+  },
+
+  /**
+   * Handle logic to enable/disable JS/cache/Service Worker testing.
+   */
+  _toggleDevToolsSettings(options) {
+    // Wait a tick so that the response packet can be dispatched before the
+    // subsequent navigation event packet.
+    let reload = false;
+
+    if (typeof options.javascriptEnabled !== "undefined" &&
+        options.javascriptEnabled !== this._getJavascriptEnabled()) {
+      this._setJavascriptEnabled(options.javascriptEnabled);
+      reload = true;
+    }
+    if (typeof options.cacheDisabled !== "undefined" &&
+        options.cacheDisabled !== this._getCacheDisabled()) {
+      this._setCacheDisabled(options.cacheDisabled);
+    }
+    if ((typeof options.serviceWorkersTestingEnabled !== "undefined") &&
+        (options.serviceWorkersTestingEnabled !==
+         this._getServiceWorkersTestingEnabled())) {
+      this._setServiceWorkersTestingEnabled(
+        options.serviceWorkersTestingEnabled
+      );
+    }
+
+    // Reload if:
+    //  - there's an explicit `performReload` flag and it's true
+    //  - there's no `performReload` flag, but it makes sense to do so
+    let hasExplicitReloadFlag = "performReload" in options;
+    if ((hasExplicitReloadFlag && options.performReload) ||
+       (!hasExplicitReloadFlag && reload)) {
+      this.onReload();
+    }
+  },
+
+  /**
+   * Opposite of the _toggleDevToolsSettings method, that reset document state
+   * when closing the toolbox.
+   */
+  _restoreDocumentSettings() {
+    this._restoreJavascript();
+    this._setCacheDisabled(false);
+    this._setServiceWorkersTestingEnabled(false);
+  },
+
+  /**
+   * Disable or enable the cache via docShell.
+   */
+  _setCacheDisabled(disabled) {
+    let enable = Ci.nsIRequest.LOAD_NORMAL;
+    let disable = Ci.nsIRequest.LOAD_BYPASS_CACHE |
+                  Ci.nsIRequest.INHIBIT_CACHING;
+
+    this.docShell.defaultLoadFlags = disabled ? disable : enable;
+  },
+
+  /**
+   * Disable or enable JS via docShell.
+   */
+  _wasJavascriptEnabled: null,
+  _setJavascriptEnabled(allow) {
+    if (this._wasJavascriptEnabled === null) {
+      this._wasJavascriptEnabled = this.docShell.allowJavascript;
+    }
+    this.docShell.allowJavascript = allow;
+  },
+
+  /**
+   * Restore JS state, before the actor modified it.
+   */
+  _restoreJavascript() {
+    if (this._wasJavascriptEnabled !== null) {
+      this._setJavascriptEnabled(this._wasJavascriptEnabled);
+      this._wasJavascriptEnabled = null;
+    }
+  },
+
+  /**
+   * Return JS allowed status.
+   */
+  _getJavascriptEnabled() {
+    if (!this.docShell) {
+      // The tab is already closed.
+      return null;
+    }
+
+    return this.docShell.allowJavascript;
+  },
+
+  /**
+   * Disable or enable the service workers testing features.
+   */
+  _setServiceWorkersTestingEnabled(enabled) {
+    let windowUtils = this.window.QueryInterface(Ci.nsIInterfaceRequestor)
+                                 .getInterface(Ci.nsIDOMWindowUtils);
+    windowUtils.serviceWorkersTestingEnabled = enabled;
+  },
+
+  /**
+   * Return cache allowed status.
+   */
+  _getCacheDisabled() {
+    if (!this.docShell) {
+      // The tab is already closed.
+      return null;
+    }
+
+    let disable = Ci.nsIRequest.LOAD_BYPASS_CACHE |
+                  Ci.nsIRequest.INHIBIT_CACHING;
+    return this.docShell.defaultLoadFlags === disable;
+  },
+
+  /**
+   * Return service workers testing allowed status.
+   */
+  _getServiceWorkersTestingEnabled() {
+    if (!this.docShell) {
+      // The tab is already closed.
+      return null;
+    }
+
+    let windowUtils = this.window.QueryInterface(Ci.nsIInterfaceRequestor)
+                                 .getInterface(Ci.nsIDOMWindowUtils);
+    return windowUtils.serviceWorkersTestingEnabled;
+  },
+
+  /**
+   * Prepare to enter a nested event loop by disabling debuggee events.
+   */
+  preNest() {
+    if (!this.window) {
+      // The tab is already closed.
+      return;
+    }
+    let windowUtils = this.window
+                          .QueryInterface(Ci.nsIInterfaceRequestor)
+                          .getInterface(Ci.nsIDOMWindowUtils);
+    windowUtils.suppressEventHandling(true);
+    windowUtils.suspendTimeouts();
+  },
+
+  /**
+   * Prepare to exit a nested event loop by enabling debuggee events.
+   */
+  postNest(nestData) {
+    if (!this.window) {
+      // The tab is already closed.
+      return;
+    }
+    let windowUtils = this.window
+                          .QueryInterface(Ci.nsIInterfaceRequestor)
+                          .getInterface(Ci.nsIDOMWindowUtils);
+    windowUtils.resumeTimeouts();
+    windowUtils.suppressEventHandling(false);
+  },
+
+  _changeTopLevelDocument(window) {
+    // Fake a will-navigate on the previous document
+    // to let a chance to unregister it
+    this._willNavigate(this.window, window.location.href, null, true);
+
+    this._windowDestroyed(this.window, null, true);
+
+    // Immediately change the window as this window, if in process of unload
+    // may already be non working on the next cycle and start throwing
+    this._setWindow(window);
+
+    DevToolsUtils.executeSoon(() => {
+      // Then fake window-ready and navigate on the given document
+      this._windowReady(window, true);
+      DevToolsUtils.executeSoon(() => {
+        this._navigate(window, true);
+      });
+    });
+  },
+
+  _setWindow(window) {
+    let docShell = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIWebNavigation)
+                         .QueryInterface(Ci.nsIDocShell);
+    // Here is the very important call where we switch the currently
+    // targeted context (it will indirectly update this.window and
+    // many other attributes defined from docShell).
+    Object.defineProperty(this, "docShell", {
+      value: docShell,
+      enumerable: true,
+      configurable: true
+    });
+    events.emit(this, "changed-toplevel-document");
+    this.conn.send({
+      from: this.actorID,
+      type: "frameUpdate",
+      selected: this.outerWindowID
+    });
+  },
+
+  /**
+   * Handle location changes, by clearing the previous debuggees and enabling
+   * debugging, which may have been disabled temporarily by the
+   * DebuggerProgressListener.
+   */
+  _windowReady(window, isFrameSwitching = false) {
+    let isTopLevel = window == this.window;
+
+    // We just reset iframe list on WillNavigate, so we now list all existing
+    // frames when we load a new document in the original window
+    if (window == this._originalWindow && !isFrameSwitching) {
+      this._updateChildDocShells();
+    }
+
+    events.emit(this, "window-ready", {
+      window: window,
+      isTopLevel: isTopLevel,
+      id: getWindowID(window)
+    });
+
+    // TODO bug 997119: move that code to ThreadActor by listening to
+    // window-ready
+    let threadActor = this.threadActor;
+    if (isTopLevel && threadActor.state != "detached") {
+      this.sources.reset({ sourceMaps: true });
+      threadActor.clearDebuggees();
+      threadActor.dbg.enabled = true;
+      threadActor.maybePauseOnExceptions();
+      // Update the global no matter if the debugger is on or off,
+      // otherwise the global will be wrong when enabled later.
+      threadActor.global = window;
+    }
+
+    // Refresh the debuggee list when a new window object appears (top window or
+    // iframe).
+    if (threadActor.attached) {
+      threadActor.dbg.addDebuggees();
+    }
+  },
+
+  _windowDestroyed(window, id = null, isFrozen = false) {
+    events.emit(this, "window-destroyed", {
+      window: window,
+      isTopLevel: window == this.window,
+      id: id || getWindowID(window),
+      isFrozen: isFrozen
+    });
+  },
+
+  /**
+   * Start notifying server and client about a new document
+   * being loaded in the currently targeted context.
+   */
+  _willNavigate(window, newURI, request, isFrameSwitching = false) {
+    let isTopLevel = window == this.window;
+    let reset = false;
+
+    if (window == this._originalWindow && !isFrameSwitching) {
+      // Clear the iframe list if the original top-level document changes.
+      this._notifyDocShellDestroyAll();
+
+      // If the top level document changes and we are targeting
+      // an iframe, we need to reset to the upcoming new top level document.
+      // But for this will-navigate event, we will dispatch on the old window.
+      // (The inspector codebase expect to receive will-navigate for the
+      // currently displayed document in order to cleanup the markup view)
+      if (this.window != this._originalWindow) {
+        reset = true;
+        window = this.window;
+        isTopLevel = true;
+      }
+    }
+
+    // will-navigate event needs to be dispatched synchronously,
+    // by calling the listeners in the order or registration.
+    // This event fires once navigation starts,
+    // (all pending user prompts are dealt with),
+    // but before the first request starts.
+    events.emit(this, "will-navigate", {
+      window: window,
+      isTopLevel: isTopLevel,
+      newURI: newURI,
+      request: request
+    });
+
+    // We don't do anything for inner frames in TabActor.
+    // (we will only update thread actor on window-ready)
+    if (!isTopLevel) {
+      return;
+    }
+
+    // Proceed normally only if the debuggee is not paused.
+    // TODO bug 997119: move that code to ThreadActor by listening to
+    // will-navigate
+    let threadActor = this.threadActor;
+    if (threadActor.state == "paused") {
+      this.conn.send(
+        threadActor.unsafeSynchronize(Promise.resolve(threadActor.onResume())));
+      threadActor.dbg.enabled = false;
+    }
+    threadActor.disableAllBreakpoints();
+
+    this.conn.send({
+      from: this.actorID,
+      type: "tabNavigated",
+      url: newURI,
+      nativeConsoleAPI: true,
+      state: "start",
+      isFrameSwitching: isFrameSwitching
+    });
+
+    if (reset) {
+      this._setWindow(this._originalWindow);
+    }
+  },
+
+  /**
+   * Notify server and client about a new document done loading in the current
+   * targeted context.
+   */
+  _navigate(window, isFrameSwitching = false) {
+    let isTopLevel = window == this.window;
+
+    // navigate event needs to be dispatched synchronously,
+    // by calling the listeners in the order or registration.
+    // This event is fired once the document is loaded,
+    // after the load event, it's document ready-state is 'complete'.
+    events.emit(this, "navigate", {
+      window: window,
+      isTopLevel: isTopLevel
+    });
+
+    // We don't do anything for inner frames in TabActor.
+    // (we will only update thread actor on window-ready)
+    if (!isTopLevel) {
+      return;
+    }
+
+    // TODO bug 997119: move that code to ThreadActor by listening to navigate
+    let threadActor = this.threadActor;
+    if (threadActor.state == "running") {
+      threadActor.dbg.enabled = true;
+    }
+
+    this.conn.send({
+      from: this.actorID,
+      type: "tabNavigated",
+      url: this.url,
+      title: this.title,
+      nativeConsoleAPI: this.hasNativeConsoleAPI(this.window),
+      state: "stop",
+      isFrameSwitching: isFrameSwitching
+    });
+  },
+
+  /**
+   * Tells if the window.console object is native or overwritten by script in
+   * the page.
+   *
+   * @param nsIDOMWindow window
+   *        The window object you want to check.
+   * @return boolean
+   *         True if the window.console object is native, or false otherwise.
+   */
+  hasNativeConsoleAPI(window) {
+    let isNative = false;
+    try {
+      // We are very explicitly examining the "console" property of
+      // the non-Xrayed object here.
+      let console = window.wrappedJSObject.console;
+      isNative = new XPCNativeWrapper(console).IS_NATIVE_CONSOLE;
+    } catch (ex) {
+      // ignore
+    }
+    return isNative;
+  },
+
+  /**
+   * Create or return the StyleSheetActor for a style sheet. This method
+   * is here because the Style Editor and Inspector share style sheet actors.
+   *
+   * @param DOMStyleSheet styleSheet
+   *        The style sheet to create an actor for.
+   * @return StyleSheetActor actor
+   *         The actor for this style sheet.
+   *
+   */
+  createStyleSheetActor(styleSheet) {
+    if (this._styleSheetActors.has(styleSheet)) {
+      return this._styleSheetActors.get(styleSheet);
+    }
+    let actor = new StyleSheetActor(styleSheet, this);
+    this._styleSheetActors.set(styleSheet, actor);
+
+    this._tabPool.addActor(actor);
+    events.emit(this, "stylesheet-added", actor);
+
+    return actor;
+  },
+
+  removeActorByName(name) {
+    if (name in this._extraActors) {
+      const actor = this._extraActors[name];
+      if (this._tabActorPool.has(actor)) {
+        this._tabActorPool.removeActor(actor);
+      }
+      delete this._extraActors[name];
+    }
+  },
+
+  /**
+   * Takes a packet containing a url, line and column and returns
+   * the updated url, line and column based on the current source mapping
+   * (source mapped files, pretty prints).
+   *
+   * @param {String} request.url
+   * @param {Number} request.line
+   * @param {Number?} request.column
+   * @return {Promise<Object>}
+   */
+  onResolveLocation(request) {
+    let { url, line } = request;
+    let column = request.column || 0;
+    const scripts = this.threadActor.dbg.findScripts({ url });
+
+    if (!scripts[0] || !scripts[0].source) {
+      return promise.resolve({
+        from: this.actorID,
+        type: "resolveLocation",
+        error: "SOURCE_NOT_FOUND"
+      });
+    }
+    const source = scripts[0].source;
+    const generatedActor = this.sources.createNonSourceMappedActor(source);
+    let generatedLocation = new GeneratedLocation(
+      generatedActor, line, column);
+    return this.sources.getOriginalLocation(generatedLocation).then(loc => {
+      // If no map found, return this packet
+      if (loc.originalLine == null) {
+        return {
+          type: "resolveLocation",
+          error: "MAP_NOT_FOUND"
+        };
+      }
+
+      loc = loc.toJSON();
+      return {
+        from: this.actorID,
+        url: loc.source.url,
+        column: loc.column,
+        line: loc.line
+      };
+    });
+  },
+};
+
+/**
+ * The request types this actor can handle.
+ */
+TabActor.prototype.requestTypes = {
+  "attach": TabActor.prototype.onAttach,
+  "detach": TabActor.prototype.onDetach,
+  "focus": TabActor.prototype.onFocus,
+  "reload": TabActor.prototype.onReload,
+  "navigateTo": TabActor.prototype.onNavigateTo,
+  "reconfigure": TabActor.prototype.onReconfigure,
+  "switchToFrame": TabActor.prototype.onSwitchToFrame,
+  "listFrames": TabActor.prototype.onListFrames,
+  "listWorkers": TabActor.prototype.onListWorkers,
+  "resolveLocation": TabActor.prototype.onResolveLocation
+};
+
+exports.TabActor = TabActor;
+
+/**
+ * Creates a tab actor for handling requests to a single browser frame.
+ * Both <xul:browser> and <iframe mozbrowser> are supported.
+ * This actor is a shim that connects to a ContentActor in a remote browser process.
+ * All RDP packets get forwarded using the message manager.
+ *
+ * @param connection The main RDP connection.
+ * @param browser <xul:browser> or <iframe mozbrowser> element to connect to.
+ */
+function BrowserTabActor(connection, browser) {
+  this._conn = connection;
+  this._browser = browser;
+  this._form = null;
+}
+
+BrowserTabActor.prototype = {
+  connect() {
+    let onDestroy = () => {
+      this._form = null;
+    };
+    let connect = DebuggerServer.connectToChild(this._conn, this._browser, onDestroy);
+    return connect.then(form => {
+      this._form = form;
+      return this;
+    });
+  },
+
+  get _tabbrowser() {
+    if (typeof this._browser.getTabBrowser == "function") {
+      return this._browser.getTabBrowser();
+    }
+    return null;
+  },
+
+  get _mm() {
+    // Get messageManager from XUL browser (which might be a specialized tunnel for RDM)
+    // or else fallback to asking the frameLoader itself.
+    return this._browser.messageManager ||
+           this._browser.frameLoader.messageManager;
+  },
+
+  update() {
+    // If the child happens to be crashed/close/detach, it won't have _form set,
+    // so only request form update if some code is still listening on the other
+    // side.
+    if (this._form) {
+      let deferred = promise.defer();
+      let onFormUpdate = msg => {
+        // There may be more than just one childtab.js up and running
+        if (this._form.actor != msg.json.actor) {
+          return;
+        }
+        this._mm.removeMessageListener("debug:form", onFormUpdate);
+        this._form = msg.json;
+        deferred.resolve(this);
+      };
+      this._mm.addMessageListener("debug:form", onFormUpdate);
+      this._mm.sendAsyncMessage("debug:form");
+      return deferred.promise;
+    }
+
+    return this.connect();
+  },
+
+  /**
+   * If we don't have a title from the content side because it's a zombie tab, try to find
+   * it on the chrome side.
+   */
+  get title() {
+    // On Fennec, we can check the session store data for zombie tabs
+    if (this._browser.__SS_restore) {
+      let sessionStore = this._browser.__SS_data;
+      // Get the last selected entry
+      let entry = sessionStore.entries[sessionStore.index - 1];
+      return entry.title;
+    }
+    // If contentTitle is empty (e.g. on a not-yet-restored tab), but there is a
+    // tabbrowser (i.e. desktop Firefox, but not Fennec), we can use the label
+    // as the title.
+    if (this._tabbrowser) {
+      let tab = this._tabbrowser.getTabForBrowser(this._browser);
+      if (tab) {
+        return tab.label;
+      }
+    }
+    return "";
+  },
+
+  /**
+   * If we don't have a url from the content side because it's a zombie tab, try to find
+   * it on the chrome side.
+   */
+  get url() {
+    // On Fennec, we can check the session store data for zombie tabs
+    if (this._browser.__SS_restore) {
+      let sessionStore = this._browser.__SS_data;
+      // Get the last selected entry
+      let entry = sessionStore.entries[sessionStore.index - 1];
+      return entry.url;
+    }
+    return null;
+  },
+
+  form() {
+    let form = Object.assign({}, this._form);
+    // In some cases, the title and url fields might be empty.  Zombie tabs (not yet
+    // restored) are a good example.  In such cases, try to look up values for these
+    // fields using other data in the parent process.
+    if (!form.title) {
+      form.title = this.title;
+    }
+    if (!form.url) {
+      form.url = this.url;
+    }
+    return form;
+  },
+
+  exit() {
+    this._browser = null;
+  },
+};
+
+exports.BrowserTabActor = BrowserTabActor;
+
+function BrowserAddonList(connection) {
+  this._connection = connection;
+  this._actorByAddonId = new Map();
+  this._onListChanged = null;
+}
+
+BrowserAddonList.prototype.getList = function () {
+  let deferred = promise.defer();
+  AddonManager.getAllAddons((addons) => {
+    for (let addon of addons) {
+      let actor = this._actorByAddonId.get(addon.id);
+      if (!actor) {
+        if (addon.isWebExtension) {
+          actor = new WebExtensionActor(this._connection, addon);
+        } else {
+          actor = new BrowserAddonActor(this._connection, addon);
+        }
+
+        this._actorByAddonId.set(addon.id, actor);
+      }
+    }
+    deferred.resolve([...this._actorByAddonId].map(([_, actor]) => actor));
+  });
+  return deferred.promise;
+};
+
+Object.defineProperty(BrowserAddonList.prototype, "onListChanged", {
+  enumerable: true,
+  configurable: true,
+  get() {
+    return this._onListChanged;
+  },
+  set(v) {
+    if (v !== null && typeof v != "function") {
+      throw new Error(
+        "onListChanged property may only be set to 'null' or a function");
+    }
+    this._onListChanged = v;
+    this._adjustListener();
+  }
+});
+
+BrowserAddonList.prototype.onInstalled = function (addon) {
+  this._notifyListChanged();
+  this._adjustListener();
+};
+
+BrowserAddonList.prototype.onUninstalled = function (addon) {
+  this._actorByAddonId.delete(addon.id);
+  this._notifyListChanged();
+  this._adjustListener();
+};
+
+BrowserAddonList.prototype._notifyListChanged = function () {
+  if (this._onListChanged) {
+    this._onListChanged();
+  }
+};
+
+BrowserAddonList.prototype._adjustListener = function () {
+  if (this._onListChanged) {
+    // As long as the callback exists, we need to listen for changes
+    // so we can notify about add-on changes.
+    AddonManager.addAddonListener(this);
+  } else if (this._actorByAddonId.size === 0) {
+    // When the callback does not exist, we only need to keep listening
+    // if the actor cache will need adjusting when add-ons change.
+    AddonManager.removeAddonListener(this);
+  }
+};
+
+exports.BrowserAddonList = BrowserAddonList;
+
+/**
+ * The DebuggerProgressListener object is an nsIWebProgressListener which
+ * handles onStateChange events for the inspected browser. If the user tries to
+ * navigate away from a paused page, the listener makes sure that the debuggee
+ * is resumed before the navigation begins.
+ *
+ * @param TabActor aTabActor
+ *        The tab actor associated with this listener.
+ */
+function DebuggerProgressListener(tabActor) {
+  this._tabActor = tabActor;
+  this._onWindowCreated = this.onWindowCreated.bind(this);
+  this._onWindowHidden = this.onWindowHidden.bind(this);
+
+  // Watch for windows destroyed (global observer that will need filtering)
+  Services.obs.addObserver(this, "inner-window-destroyed", false);
+
+  // XXX: for now we maintain the list of windows we know about in this instance
+  // so that we can discriminate windows we care about when observing
+  // inner-window-destroyed events. Bug 1016952 would remove the need for this.
+  this._knownWindowIDs = new Map();
+
+  this._watchedDocShells = new WeakSet();
+}
+
+DebuggerProgressListener.prototype = {
+  QueryInterface: XPCOMUtils.generateQI([
+    Ci.nsIWebProgressListener,
+    Ci.nsISupportsWeakReference,
+    Ci.nsISupports,
+  ]),
+
+  destroy() {
+    Services.obs.removeObserver(this, "inner-window-destroyed", false);
+    this._knownWindowIDs.clear();
+    this._knownWindowIDs = null;
+  },
+
+  watch(docShell) {
+    // Add the docshell to the watched set. We're actually adding the window,
+    // because docShell objects are not wrappercached and would be rejected
+    // by the WeakSet.
+    let docShellWindow = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                                 .getInterface(Ci.nsIDOMWindow);
+    this._watchedDocShells.add(docShellWindow);
+
+    let webProgress = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                              .getInterface(Ci.nsIWebProgress);
+    webProgress.addProgressListener(this,
+                                    Ci.nsIWebProgress.NOTIFY_STATUS |
+                                    Ci.nsIWebProgress.NOTIFY_STATE_WINDOW |
+                                    Ci.nsIWebProgress.NOTIFY_STATE_DOCUMENT);
+
+    let handler = getDocShellChromeEventHandler(docShell);
+    handler.addEventListener("DOMWindowCreated", this._onWindowCreated, true);
+    handler.addEventListener("pageshow", this._onWindowCreated, true);
+    handler.addEventListener("pagehide", this._onWindowHidden, true);
+
+    // Dispatch the _windowReady event on the tabActor for pre-existing windows
+    for (let win of this._getWindowsInDocShell(docShell)) {
+      this._tabActor._windowReady(win);
+      this._knownWindowIDs.set(getWindowID(win), win);
+    }
+  },
+
+  unwatch(docShell) {
+    let docShellWindow = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                                 .getInterface(Ci.nsIDOMWindow);
+    if (!this._watchedDocShells.has(docShellWindow)) {
+      return;
+    }
+
+    let webProgress = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                              .getInterface(Ci.nsIWebProgress);
+    // During process shutdown, the docshell may already be cleaned up and throw
+    try {
+      webProgress.removeProgressListener(this);
+    } catch (e) {
+      // ignore
+    }
+
+    let handler = getDocShellChromeEventHandler(docShell);
+    handler.removeEventListener("DOMWindowCreated",
+      this._onWindowCreated, true);
+    handler.removeEventListener("pageshow", this._onWindowCreated, true);
+    handler.removeEventListener("pagehide", this._onWindowHidden, true);
+
+    for (let win of this._getWindowsInDocShell(docShell)) {
+      this._knownWindowIDs.delete(getWindowID(win));
+    }
+  },
+
+  _getWindowsInDocShell(docShell) {
+    return getChildDocShells(docShell).map(d => {
+      return d.QueryInterface(Ci.nsIInterfaceRequestor)
+              .getInterface(Ci.nsIDOMWindow);
+    });
+  },
+
+  onWindowCreated: DevToolsUtils.makeInfallible(function (evt) {
+    if (!this._tabActor.attached) {
+      return;
+    }
+
+    // pageshow events for non-persisted pages have already been handled by a
+    // prior DOMWindowCreated event. For persisted pages, act as if the window
+    // had just been created since it's been unfrozen from bfcache.
+    if (evt.type == "pageshow" && !evt.persisted) {
+      return;
+    }
+
+    let window = evt.target.defaultView;
+    this._tabActor._windowReady(window);
+
+    if (evt.type !== "pageshow") {
+      this._knownWindowIDs.set(getWindowID(window), window);
+    }
+  }, "DebuggerProgressListener.prototype.onWindowCreated"),
+
+  onWindowHidden: DevToolsUtils.makeInfallible(function (evt) {
+    if (!this._tabActor.attached) {
+      return;
+    }
+
+    // Only act as if the window has been destroyed if the 'pagehide' event
+    // was sent for a persisted window (persisted is set when the page is put
+    // and frozen in the bfcache). If the page isn't persisted, the observer's
+    // inner-window-destroyed event will handle it.
+    if (!evt.persisted) {
+      return;
+    }
+
+    let window = evt.target.defaultView;
+    this._tabActor._windowDestroyed(window, null, true);
+  }, "DebuggerProgressListener.prototype.onWindowHidden"),
+
+  observe: DevToolsUtils.makeInfallible(function (subject, topic) {
+    if (!this._tabActor.attached) {
+      return;
+    }
+
+    // Because this observer will be called for all inner-window-destroyed in
+    // the application, we need to filter out events for windows we are not
+    // watching
+    let innerID = subject.QueryInterface(Ci.nsISupportsPRUint64).data;
+    let window = this._knownWindowIDs.get(innerID);
+    if (window) {
+      this._knownWindowIDs.delete(innerID);
+      this._tabActor._windowDestroyed(window, innerID);
+    }
+  }, "DebuggerProgressListener.prototype.observe"),
+
+  onStateChange:
+  DevToolsUtils.makeInfallible(function (progress, request, flag, status) {
+    if (!this._tabActor.attached) {
+      return;
+    }
+
+    let isStart = flag & Ci.nsIWebProgressListener.STATE_START;
+    let isStop = flag & Ci.nsIWebProgressListener.STATE_STOP;
+    let isDocument = flag & Ci.nsIWebProgressListener.STATE_IS_DOCUMENT;
+    let isWindow = flag & Ci.nsIWebProgressListener.STATE_IS_WINDOW;
+
+    // Catch any iframe location change
+    if (isDocument && isStop) {
+      // Watch document stop to ensure having the new iframe url.
+      progress.QueryInterface(Ci.nsIDocShell);
+      this._tabActor._notifyDocShellsUpdate([progress]);
+    }
+
+    let window = progress.DOMWindow;
+    if (isDocument && isStart) {
+      // One of the earliest events that tells us a new URI
+      // is being loaded in this window.
+      let newURI = request instanceof Ci.nsIChannel ? request.URI.spec : null;
+      this._tabActor._willNavigate(window, newURI, request);
+    }
+    if (isWindow && isStop) {
+      // Don't dispatch "navigate" event just yet when there is a redirect to
+      // about:neterror page.
+      if (request.status != Cr.NS_OK) {
+        // Instead, listen for DOMContentLoaded as about:neterror is loaded
+        // with LOAD_BACKGROUND flags and never dispatches load event.
+        // That may be the same reason why there is no onStateChange event
+        // for about:neterror loads.
+        let handler = getDocShellChromeEventHandler(progress);
+        let onLoad = evt => {
+          // Ignore events from iframes
+          if (evt.target == window.document) {
+            handler.removeEventListener("DOMContentLoaded", onLoad, true);
+            this._tabActor._navigate(window);
+          }
+        };
+        handler.addEventListener("DOMContentLoaded", onLoad, true);
+      } else {
+        // Somewhat equivalent of load event.
+        // (window.document.readyState == complete)
+        this._tabActor._navigate(window);
+      }
+    }
+  }, "DebuggerProgressListener.prototype.onStateChange")
+};
+
+exports.register = function (handle) {
+  handle.setRootActor(createRootActor);
+};
+
+exports.unregister = function (handle) {
+  handle.setRootActor(null);
+};
diff --git a/devtools/server/actors/webconsole.js b/devtools/server/actors/webconsole.js
new file mode 100644
index 000000000..9712ff32d
--- /dev/null
+++ b/devtools/server/actors/webconsole.js
@@ -0,0 +1,2346 @@
+/* -*- js-indent-level: 2; indent-tabs-mode: nil -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const Services = require("Services");
+const { Cc, Ci, Cu } = require("chrome");
+const { DebuggerServer, ActorPool } = require("devtools/server/main");
+const { EnvironmentActor } = require("devtools/server/actors/environment");
+const { ThreadActor } = require("devtools/server/actors/script");
+const { ObjectActor, LongStringActor, createValueGrip, stringIsLong } = require("devtools/server/actors/object");
+const DevToolsUtils = require("devtools/shared/DevToolsUtils");
+const ErrorDocs = require("devtools/server/actors/errordocs");
+
+loader.lazyRequireGetter(this, "NetworkMonitor", "devtools/shared/webconsole/network-monitor", true);
+loader.lazyRequireGetter(this, "NetworkMonitorChild", "devtools/shared/webconsole/network-monitor", true);
+loader.lazyRequireGetter(this, "ConsoleProgressListener", "devtools/shared/webconsole/network-monitor", true);
+loader.lazyRequireGetter(this, "StackTraceCollector", "devtools/shared/webconsole/network-monitor", true);
+loader.lazyRequireGetter(this, "events", "sdk/event/core");
+loader.lazyRequireGetter(this, "ServerLoggingListener", "devtools/shared/webconsole/server-logger", true);
+loader.lazyRequireGetter(this, "JSPropertyProvider", "devtools/shared/webconsole/js-property-provider", true);
+loader.lazyRequireGetter(this, "Parser", "resource://devtools/shared/Parser.jsm", true);
+loader.lazyRequireGetter(this, "NetUtil", "resource://gre/modules/NetUtil.jsm", true);
+
+for (let name of ["WebConsoleUtils", "ConsoleServiceListener",
+    "ConsoleAPIListener", "addWebConsoleCommands",
+    "ConsoleReflowListener", "CONSOLE_WORKER_IDS"]) {
+  Object.defineProperty(this, name, {
+    get: function (prop) {
+      if (prop == "WebConsoleUtils") {
+        prop = "Utils";
+      }
+      if (isWorker) {
+        return require("devtools/server/actors/utils/webconsole-worker-utils")[prop];
+      } else {
+        return require("devtools/server/actors/utils/webconsole-utils")[prop];
+      }
+    }.bind(null, name),
+    configurable: true,
+    enumerable: true
+  });
+}
+
+/**
+ * The WebConsoleActor implements capabilities needed for the Web Console
+ * feature.
+ *
+ * @constructor
+ * @param object aConnection
+ *        The connection to the client, DebuggerServerConnection.
+ * @param object [aParentActor]
+ *        Optional, the parent actor.
+ */
+function WebConsoleActor(aConnection, aParentActor)
+{
+  this.conn = aConnection;
+  this.parentActor = aParentActor;
+
+  this._actorPool = new ActorPool(this.conn);
+  this.conn.addActorPool(this._actorPool);
+
+  this._prefs = {};
+
+  this.dbg = this.parentActor.makeDebugger();
+
+  this._netEvents = new Map();
+  this._gripDepth = 0;
+  this._listeners = new Set();
+  this._lastConsoleInputEvaluation = undefined;
+
+  this.objectGrip = this.objectGrip.bind(this);
+  this._onWillNavigate = this._onWillNavigate.bind(this);
+  this._onChangedToplevelDocument = this._onChangedToplevelDocument.bind(this);
+  events.on(this.parentActor, "changed-toplevel-document", this._onChangedToplevelDocument);
+  this._onObserverNotification = this._onObserverNotification.bind(this);
+  if (this.parentActor.isRootActor) {
+    Services.obs.addObserver(this._onObserverNotification,
+                             "last-pb-context-exited", false);
+  }
+
+  this.traits = {
+    customNetworkRequest: !this._parentIsContentActor,
+    evaluateJSAsync: true,
+    transferredResponseSize: true,
+    selectedObjectActor: true, // 44+
+  };
+}
+
+WebConsoleActor.prototype =
+{
+  /**
+   * Debugger instance.
+   *
+   * @see jsdebugger.jsm
+   */
+  dbg: null,
+
+  /**
+   * This is used by the ObjectActor to keep track of the depth of grip() calls.
+   * @private
+   * @type number
+   */
+  _gripDepth: null,
+
+  /**
+   * Actor pool for all of the actors we send to the client.
+   * @private
+   * @type object
+   * @see ActorPool
+   */
+  _actorPool: null,
+
+  /**
+   * Web Console-related preferences.
+   * @private
+   * @type object
+   */
+  _prefs: null,
+
+  /**
+   * Holds a map between nsIChannel objects and NetworkEventActors for requests
+   * created with sendHTTPRequest.
+   *
+   * @private
+   * @type Map
+   */
+  _netEvents: null,
+
+  /**
+   * Holds a set of all currently registered listeners.
+   *
+   * @private
+   * @type Set
+   */
+  _listeners: null,
+
+  /**
+   * The debugger server connection instance.
+   * @type object
+   */
+  conn: null,
+
+  /**
+   * List of supported features by the console actor.
+   * @type object
+   */
+  traits: null,
+
+  /**
+   * Boolean getter that tells if the parent actor is a ContentActor.
+   *
+   * @private
+   * @type boolean
+   */
+  get _parentIsContentActor() {
+    return "ContentActor" in DebuggerServer &&
+            this.parentActor instanceof DebuggerServer.ContentActor;
+  },
+
+  /**
+   * The window or sandbox we work with.
+   * Note that even if it is named `window` it refers to the current
+   * global we are debugging, which can be a Sandbox for addons
+   * or browser content toolbox.
+   *
+   * @type nsIDOMWindow or Sandbox
+   */
+  get window() {
+    if (this.parentActor.isRootActor) {
+      return this._getWindowForBrowserConsole();
+    }
+    return this.parentActor.window;
+  },
+
+  /**
+   * Get a window to use for the browser console.
+   *
+   * @private
+   * @return nsIDOMWindow
+   *         The window to use, or null if no window could be found.
+   */
+  _getWindowForBrowserConsole: function WCA__getWindowForBrowserConsole()
+  {
+    // Check if our last used chrome window is still live.
+    let window = this._lastChromeWindow && this._lastChromeWindow.get();
+    // If not, look for a new one.
+    if (!window || window.closed) {
+      window = this.parentActor.window;
+      if (!window) {
+        // Try to find the Browser Console window to use instead.
+        window = Services.wm.getMostRecentWindow("devtools:webconsole");
+        // We prefer the normal chrome window over the console window,
+        // so we'll look for those windows in order to replace our reference.
+        let onChromeWindowOpened = () => {
+          // We'll look for this window when someone next requests window()
+          Services.obs.removeObserver(onChromeWindowOpened, "domwindowopened");
+          this._lastChromeWindow = null;
+        };
+        Services.obs.addObserver(onChromeWindowOpened, "domwindowopened", false);
+      }
+
+      this._handleNewWindow(window);
+    }
+
+    return window;
+  },
+
+  /**
+   * Store a newly found window on the actor to be used in the future.
+   *
+   * @private
+   * @param nsIDOMWindow window
+   *        The window to store on the actor (can be null).
+   */
+  _handleNewWindow: function WCA__handleNewWindow(window)
+  {
+    if (window) {
+      if (this._hadChromeWindow) {
+        Services.console.logStringMessage('Webconsole context has changed');
+      }
+      this._lastChromeWindow = Cu.getWeakReference(window);
+      this._hadChromeWindow = true;
+    } else {
+      this._lastChromeWindow = null;
+    }
+  },
+
+  /**
+   * Whether we've been using a window before.
+   *
+   * @private
+   * @type boolean
+   */
+  _hadChromeWindow: false,
+
+  /**
+   * A weak reference to the last chrome window we used to work with.
+   *
+   * @private
+   * @type nsIWeakReference
+   */
+  _lastChromeWindow: null,
+
+  // The evalWindow is used at the scope for JS evaluation.
+  _evalWindow: null,
+  get evalWindow() {
+    return this._evalWindow || this.window;
+  },
+
+  set evalWindow(aWindow) {
+    this._evalWindow = aWindow;
+
+    if (!this._progressListenerActive) {
+      events.on(this.parentActor, "will-navigate", this._onWillNavigate);
+      this._progressListenerActive = true;
+    }
+  },
+
+  /**
+   * Flag used to track if we are listening for events from the progress
+   * listener of the tab actor. We use the progress listener to clear
+   * this.evalWindow on page navigation.
+   *
+   * @private
+   * @type boolean
+   */
+  _progressListenerActive: false,
+
+  /**
+   * The ConsoleServiceListener instance.
+   * @type object
+   */
+  consoleServiceListener: null,
+
+  /**
+   * The ConsoleAPIListener instance.
+   */
+  consoleAPIListener: null,
+
+  /**
+   * The NetworkMonitor instance.
+   */
+  networkMonitor: null,
+
+  /**
+   * The NetworkMonitor instance living in the same (child) process.
+   */
+  networkMonitorChild: null,
+
+  /**
+   * The ConsoleProgressListener instance.
+   */
+  consoleProgressListener: null,
+
+  /**
+   * The ConsoleReflowListener instance.
+   */
+  consoleReflowListener: null,
+
+  /**
+   * The Web Console Commands names cache.
+   * @private
+   * @type array
+   */
+  _webConsoleCommandsCache: null,
+
+  actorPrefix: "console",
+
+  get globalDebugObject() {
+    return this.parentActor.threadActor.globalDebugObject;
+  },
+
+  grip: function WCA_grip()
+  {
+    return { actor: this.actorID };
+  },
+
+  hasNativeConsoleAPI: function WCA_hasNativeConsoleAPI(aWindow) {
+    let isNative = false;
+    try {
+      // We are very explicitly examining the "console" property of
+      // the non-Xrayed object here.
+      let console = aWindow.wrappedJSObject.console;
+      isNative = new XPCNativeWrapper(console).IS_NATIVE_CONSOLE
+    }
+    catch (ex) { }
+    return isNative;
+  },
+
+  _findProtoChain: ThreadActor.prototype._findProtoChain,
+  _removeFromProtoChain: ThreadActor.prototype._removeFromProtoChain,
+
+  /**
+   * Destroy the current WebConsoleActor instance.
+   */
+  disconnect: function WCA_disconnect()
+  {
+    if (this.consoleServiceListener) {
+      this.consoleServiceListener.destroy();
+      this.consoleServiceListener = null;
+    }
+    if (this.consoleAPIListener) {
+      this.consoleAPIListener.destroy();
+      this.consoleAPIListener = null;
+    }
+    if (this.networkMonitor) {
+      this.networkMonitor.destroy();
+      this.networkMonitor = null;
+    }
+    if (this.networkMonitorChild) {
+      this.networkMonitorChild.destroy();
+      this.networkMonitorChild = null;
+    }
+    if (this.stackTraceCollector) {
+      this.stackTraceCollector.destroy();
+      this.stackTraceCollector = null;
+    }
+    if (this.consoleProgressListener) {
+      this.consoleProgressListener.destroy();
+      this.consoleProgressListener = null;
+    }
+    if (this.consoleReflowListener) {
+      this.consoleReflowListener.destroy();
+      this.consoleReflowListener = null;
+    }
+    if (this.serverLoggingListener) {
+      this.serverLoggingListener.destroy();
+      this.serverLoggingListener = null;
+    }
+
+    events.off(this.parentActor, "changed-toplevel-document",
+               this._onChangedToplevelDocument);
+
+    this.conn.removeActorPool(this._actorPool);
+
+    if (this.parentActor.isRootActor) {
+      Services.obs.removeObserver(this._onObserverNotification,
+                                  "last-pb-context-exited");
+    }
+
+    this._actorPool = null;
+    this._webConsoleCommandsCache = null;
+    this._lastConsoleInputEvaluation = null;
+    this._evalWindow = null;
+    this._netEvents.clear();
+    this.dbg.enabled = false;
+    this.dbg = null;
+    this.conn = null;
+  },
+
+  /**
+   * Create and return an environment actor that corresponds to the provided
+   * Debugger.Environment. This is a straightforward clone of the ThreadActor's
+   * method except that it stores the environment actor in the web console
+   * actor's pool.
+   *
+   * @param Debugger.Environment aEnvironment
+   *        The lexical environment we want to extract.
+   * @return The EnvironmentActor for aEnvironment or undefined for host
+   *         functions or functions scoped to a non-debuggee global.
+   */
+  createEnvironmentActor: function WCA_createEnvironmentActor(aEnvironment) {
+    if (!aEnvironment) {
+      return undefined;
+    }
+
+    if (aEnvironment.actor) {
+      return aEnvironment.actor;
+    }
+
+    let actor = new EnvironmentActor(aEnvironment, this);
+    this._actorPool.addActor(actor);
+    aEnvironment.actor = actor;
+
+    return actor;
+  },
+
+  /**
+   * Create a grip for the given value.
+   *
+   * @param mixed aValue
+   * @return object
+   */
+  createValueGrip: function WCA_createValueGrip(aValue)
+  {
+    return createValueGrip(aValue, this._actorPool, this.objectGrip);
+  },
+
+  /**
+   * Make a debuggee value for the given value.
+   *
+   * @param mixed aValue
+   *        The value you want to get a debuggee value for.
+   * @param boolean aUseObjectGlobal
+   *        If |true| the object global is determined and added as a debuggee,
+   *        otherwise |this.window| is used when makeDebuggeeValue() is invoked.
+   * @return object
+   *         Debuggee value for |aValue|.
+   */
+  makeDebuggeeValue: function WCA_makeDebuggeeValue(aValue, aUseObjectGlobal)
+  {
+    if (aUseObjectGlobal && typeof aValue == "object") {
+      try {
+        let global = Cu.getGlobalForObject(aValue);
+        let dbgGlobal = this.dbg.makeGlobalObjectReference(global);
+        return dbgGlobal.makeDebuggeeValue(aValue);
+      }
+      catch (ex) {
+        // The above can throw an exception if aValue is not an actual object
+        // or 'Object in compartment marked as invisible to Debugger'
+      }
+    }
+    let dbgGlobal = this.dbg.makeGlobalObjectReference(this.window);
+    return dbgGlobal.makeDebuggeeValue(aValue);
+  },
+
+  /**
+   * Create a grip for the given object.
+   *
+   * @param object aObject
+   *        The object you want.
+   * @param object aPool
+   *        An ActorPool where the new actor instance is added.
+   * @param object
+   *        The object grip.
+   */
+  objectGrip: function WCA_objectGrip(aObject, aPool)
+  {
+    let actor = new ObjectActor(aObject, {
+      getGripDepth: () => this._gripDepth,
+      incrementGripDepth: () => this._gripDepth++,
+      decrementGripDepth: () => this._gripDepth--,
+      createValueGrip: v => this.createValueGrip(v),
+      sources: () => DevToolsUtils.reportException("WebConsoleActor",
+        Error("sources not yet implemented")),
+      createEnvironmentActor: (env) => this.createEnvironmentActor(env),
+      getGlobalDebugObject: () => this.globalDebugObject
+    });
+    aPool.addActor(actor);
+    return actor.grip();
+  },
+
+  /**
+   * Create a grip for the given string.
+   *
+   * @param string aString
+   *        The string you want to create the grip for.
+   * @param object aPool
+   *        An ActorPool where the new actor instance is added.
+   * @return object
+   *         A LongStringActor object that wraps the given string.
+   */
+  longStringGrip: function WCA_longStringGrip(aString, aPool)
+  {
+    let actor = new LongStringActor(aString);
+    aPool.addActor(actor);
+    return actor.grip();
+  },
+
+  /**
+   * Create a long string grip if needed for the given string.
+   *
+   * @private
+   * @param string aString
+   *        The string you want to create a long string grip for.
+   * @return string|object
+   *         A string is returned if |aString| is not a long string.
+   *         A LongStringActor grip is returned if |aString| is a long string.
+   */
+  _createStringGrip: function NEA__createStringGrip(aString)
+  {
+    if (aString && stringIsLong(aString)) {
+      return this.longStringGrip(aString, this._actorPool);
+    }
+    return aString;
+  },
+
+  /**
+   * Get an object actor by its ID.
+   *
+   * @param string aActorID
+   * @return object
+   */
+  getActorByID: function WCA_getActorByID(aActorID)
+  {
+    return this._actorPool.get(aActorID);
+  },
+
+  /**
+   * Release an actor.
+   *
+   * @param object aActor
+   *        The actor instance you want to release.
+   */
+  releaseActor: function WCA_releaseActor(aActor)
+  {
+    this._actorPool.removeActor(aActor.actorID);
+  },
+
+  /**
+   * Returns the latest web console input evaluation.
+   * This is undefined if no evaluations have been completed.
+   *
+   * @return object
+   */
+  getLastConsoleInputEvaluation: function WCU_getLastConsoleInputEvaluation()
+  {
+    return this._lastConsoleInputEvaluation;
+  },
+
+  // Request handlers for known packet types.
+
+  /**
+   * Handler for the "startListeners" request.
+   *
+   * @param object aRequest
+   *        The JSON request object received from the Web Console client.
+   * @return object
+   *         The response object which holds the startedListeners array.
+   */
+  onStartListeners: function WCA_onStartListeners(aRequest)
+  {
+    // XXXworkers: Not handling the Console API yet for workers (Bug 1209353).
+    if (isWorker) {
+      aRequest.listeners = [];
+    }
+
+    let startedListeners = [];
+    let window = !this.parentActor.isRootActor ? this.window : null;
+    let appId = null;
+    let messageManager = null;
+
+    if (this._parentIsContentActor) {
+      appId = this.parentActor.docShell.appId;
+      messageManager = this.parentActor.messageManager;
+    }
+
+    while (aRequest.listeners.length > 0) {
+      let listener = aRequest.listeners.shift();
+      switch (listener) {
+        case "PageError":
+          if (!this.consoleServiceListener) {
+            this.consoleServiceListener =
+              new ConsoleServiceListener(window, this);
+            this.consoleServiceListener.init();
+          }
+          startedListeners.push(listener);
+          break;
+        case "ConsoleAPI":
+          if (!this.consoleAPIListener) {
+            // Create the consoleAPIListener (and apply the filtering options defined
+            // in the parent actor).
+            this.consoleAPIListener =
+              new ConsoleAPIListener(window, this,
+                                     this.parentActor.consoleAPIListenerOptions);
+            this.consoleAPIListener.init();
+          }
+          startedListeners.push(listener);
+          break;
+        case "NetworkActivity":
+          if (!this.networkMonitor) {
+            // Create a StackTraceCollector that's going to be shared both by the
+            // NetworkMonitorChild (getting messages about requests from parent) and
+            // by the NetworkMonitor that directly watches service workers requests.
+            this.stackTraceCollector = new StackTraceCollector({ window, appId });
+            this.stackTraceCollector.init();
+
+            let processBoundary = Services.appinfo.processType !=
+                                  Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+            if ((appId || messageManager) && processBoundary) {
+              // Start a network monitor in the parent process to listen to
+              // most requests than happen in parent
+              this.networkMonitor =
+                new NetworkMonitorChild(appId, this.parentActor.outerWindowID,
+                                        messageManager, this.conn, this);
+              this.networkMonitor.init();
+              // Spawn also one in the child to listen to service workers
+              this.networkMonitorChild = new NetworkMonitor({ window }, this);
+              this.networkMonitorChild.init();
+            } else {
+              this.networkMonitor = new NetworkMonitor({ window }, this);
+              this.networkMonitor.init();
+            }
+          }
+          startedListeners.push(listener);
+          break;
+        case "FileActivity":
+          if (this.window instanceof Ci.nsIDOMWindow) {
+            if (!this.consoleProgressListener) {
+              this.consoleProgressListener =
+                new ConsoleProgressListener(this.window, this);
+            }
+            this.consoleProgressListener.startMonitor(this.consoleProgressListener.
+                                                      MONITOR_FILE_ACTIVITY);
+            startedListeners.push(listener);
+          }
+          break;
+        case "ReflowActivity":
+          if (!this.consoleReflowListener) {
+            this.consoleReflowListener =
+              new ConsoleReflowListener(this.window, this);
+          }
+          startedListeners.push(listener);
+          break;
+        case "ServerLogging":
+          if (!this.serverLoggingListener) {
+            this.serverLoggingListener =
+              new ServerLoggingListener(this.window, this);
+          }
+          startedListeners.push(listener);
+          break;
+      }
+    }
+
+    // Update the live list of running listeners
+    startedListeners.forEach(this._listeners.add, this._listeners);
+
+    return {
+      startedListeners: startedListeners,
+      nativeConsoleAPI: this.hasNativeConsoleAPI(this.window),
+      traits: this.traits,
+    };
+  },
+
+  /**
+   * Handler for the "stopListeners" request.
+   *
+   * @param object aRequest
+   *        The JSON request object received from the Web Console client.
+   * @return object
+   *         The response packet to send to the client: holds the
+   *         stoppedListeners array.
+   */
+  onStopListeners: function WCA_onStopListeners(aRequest)
+  {
+    let stoppedListeners = [];
+
+    // If no specific listeners are requested to be detached, we stop all
+    // listeners.
+    let toDetach = aRequest.listeners ||
+                   ["PageError", "ConsoleAPI", "NetworkActivity",
+                    "FileActivity", "ServerLogging"];
+
+    while (toDetach.length > 0) {
+      let listener = toDetach.shift();
+      switch (listener) {
+        case "PageError":
+          if (this.consoleServiceListener) {
+            this.consoleServiceListener.destroy();
+            this.consoleServiceListener = null;
+          }
+          stoppedListeners.push(listener);
+          break;
+        case "ConsoleAPI":
+          if (this.consoleAPIListener) {
+            this.consoleAPIListener.destroy();
+            this.consoleAPIListener = null;
+          }
+          stoppedListeners.push(listener);
+          break;
+        case "NetworkActivity":
+          if (this.networkMonitor) {
+            this.networkMonitor.destroy();
+            this.networkMonitor = null;
+          }
+          if (this.networkMonitorChild) {
+            this.networkMonitorChild.destroy();
+            this.networkMonitorChild = null;
+          }
+          if (this.stackTraceCollector) {
+            this.stackTraceCollector.destroy();
+            this.stackTraceCollector = null;
+          }
+          stoppedListeners.push(listener);
+          break;
+        case "FileActivity":
+          if (this.consoleProgressListener) {
+            this.consoleProgressListener.stopMonitor(this.consoleProgressListener.
+                                                     MONITOR_FILE_ACTIVITY);
+            this.consoleProgressListener = null;
+          }
+          stoppedListeners.push(listener);
+          break;
+        case "ReflowActivity":
+          if (this.consoleReflowListener) {
+            this.consoleReflowListener.destroy();
+            this.consoleReflowListener = null;
+          }
+          stoppedListeners.push(listener);
+          break;
+        case "ServerLogging":
+          if (this.serverLoggingListener) {
+            this.serverLoggingListener.destroy();
+            this.serverLoggingListener = null;
+          }
+          stoppedListeners.push(listener);
+          break;
+      }
+    }
+
+    // Update the live list of running listeners
+    stoppedListeners.forEach(this._listeners.delete, this._listeners);
+
+    return { stoppedListeners: stoppedListeners };
+  },
+
+  /**
+   * Handler for the "getCachedMessages" request. This method sends the cached
+   * error messages and the window.console API calls to the client.
+   *
+   * @param object aRequest
+   *        The JSON request object received from the Web Console client.
+   * @return object
+   *         The response packet to send to the client: it holds the cached
+   *         messages array.
+   */
+  onGetCachedMessages: function WCA_onGetCachedMessages(aRequest)
+  {
+    let types = aRequest.messageTypes;
+    if (!types) {
+      return {
+        error: "missingParameter",
+        message: "The messageTypes parameter is missing.",
+      };
+    }
+
+    let messages = [];
+
+    while (types.length > 0) {
+      let type = types.shift();
+      switch (type) {
+        case "ConsoleAPI": {
+          if (!this.consoleAPIListener) {
+            break;
+          }
+
+          // See `window` definition. It isn't always a DOM Window.
+          let requestStartTime = this.window && this.window.performance ?
+            this.window.performance.timing.requestStart : 0;
+
+          let cache = this.consoleAPIListener
+                      .getCachedMessages(!this.parentActor.isRootActor);
+          cache.forEach((aMessage) => {
+            // Filter out messages that came from a ServiceWorker but happened
+            // before the page was requested.
+            if (aMessage.innerID === "ServiceWorker" &&
+                requestStartTime > aMessage.timeStamp) {
+              return;
+            }
+
+            let message = this.prepareConsoleMessageForRemote(aMessage);
+            message._type = type;
+            messages.push(message);
+          });
+          break;
+        }
+        case "PageError": {
+          if (!this.consoleServiceListener) {
+            break;
+          }
+          let cache = this.consoleServiceListener
+                      .getCachedMessages(!this.parentActor.isRootActor);
+          cache.forEach((aMessage) => {
+            let message = null;
+            if (aMessage instanceof Ci.nsIScriptError) {
+              message = this.preparePageErrorForRemote(aMessage);
+              message._type = type;
+            }
+            else {
+              message = {
+                _type: "LogMessage",
+                message: this._createStringGrip(aMessage.message),
+                timeStamp: aMessage.timeStamp,
+              };
+            }
+            messages.push(message);
+          });
+          break;
+        }
+      }
+    }
+
+    return {
+      from: this.actorID,
+      messages: messages,
+    };
+  },
+
+  /**
+   * Handler for the "evaluateJSAsync" request. This method evaluates the given
+   * JavaScript string and sends back a packet with a unique ID.
+   * The result will be returned later as an unsolicited `evaluationResult`,
+   * that can be associated back to this request via the `resultID` field.
+   *
+   * @param object aRequest
+   *        The JSON request object received from the Web Console client.
+   * @return object
+   *         The response packet to send to with the unique id in the
+   *         `resultID` field.
+   */
+  onEvaluateJSAsync: function WCA_onEvaluateJSAsync(aRequest)
+  {
+    // We want to be able to run console commands without waiting
+    // for the first to return (see Bug 1088861).
+
+    // First, send a response packet with the id only.
+    let resultID = Date.now();
+    this.conn.send({
+      from: this.actorID,
+      resultID: resultID
+    });
+
+    // Then, execute the script that may pause.
+    let response = this.onEvaluateJS(aRequest);
+    response.resultID = resultID;
+
+    // Finally, send an unsolicited evaluationResult packet with
+    // the normal return value
+    this.conn.sendActorEvent(this.actorID, "evaluationResult", response);
+  },
+
+  /**
+   * Handler for the "evaluateJS" request. This method evaluates the given
+   * JavaScript string and sends back the result.
+   *
+   * @param object aRequest
+   *        The JSON request object received from the Web Console client.
+   * @return object
+   *         The evaluation response packet.
+   */
+  onEvaluateJS: function WCA_onEvaluateJS(aRequest)
+  {
+    let input = aRequest.text;
+    let timestamp = Date.now();
+
+    let evalOptions = {
+      bindObjectActor: aRequest.bindObjectActor,
+      frameActor: aRequest.frameActor,
+      url: aRequest.url,
+      selectedNodeActor: aRequest.selectedNodeActor,
+      selectedObjectActor: aRequest.selectedObjectActor,
+    };
+
+    let evalInfo = this.evalWithDebugger(input, evalOptions);
+    let evalResult = evalInfo.result;
+    let helperResult = evalInfo.helperResult;
+
+    let result, errorDocURL, errorMessage, errorGrip = null, frame = null;
+    if (evalResult) {
+      if ("return" in evalResult) {
+        result = evalResult.return;
+      } else if ("yield" in evalResult) {
+        result = evalResult.yield;
+      } else if ("throw" in evalResult) {
+        let error = evalResult.throw;
+
+        errorGrip = this.createValueGrip(error);
+
+        errorMessage = String(error);
+        if (typeof error === "object" && error !== null) {
+          try {
+            errorMessage = DevToolsUtils.callPropertyOnObject(error, "toString");
+          } catch (e) {
+            // If the debuggee is not allowed to access the "toString" property
+            // of the error object, calling this property from the debuggee's
+            // compartment will fail. The debugger should show the error object
+            // as it is seen by the debuggee, so this behavior is correct.
+            //
+            // Unfortunately, we have at least one test that assumes calling the
+            // "toString" property of an error object will succeed if the
+            // debugger is allowed to access it, regardless of whether the
+            // debuggee is allowed to access it or not.
+            //
+            // To accomodate these tests, if calling the "toString" property
+            // from the debuggee compartment fails, we rewrap the error object
+            // in the debugger's compartment, and then call the "toString"
+            // property from there.
+            if (typeof error.unsafeDereference === "function") {
+              errorMessage = error.unsafeDereference().toString();
+            }
+          }
+        }
+
+        // It is possible that we won't have permission to unwrap an
+        // object and retrieve its errorMessageName.
+        try {
+          errorDocURL = ErrorDocs.GetURL(error);
+        } catch (ex) {}
+
+        try {
+          let line = error.errorLineNumber;
+          let column = error.errorColumnNumber;
+
+          if (typeof line === "number" && typeof column === "number") {
+            // Set frame only if we have line/column numbers.
+            frame = {
+              source: "debugger eval code",
+              line,
+              column
+            };
+          }
+        } catch (ex) {}
+      }
+    }
+
+    // If a value is encountered that the debugger server doesn't support yet,
+    // the console should remain functional.
+    let resultGrip;
+    try {
+      resultGrip = this.createValueGrip(result);
+    } catch (e) {
+      errorMessage = e;
+    }
+
+    this._lastConsoleInputEvaluation = result;
+
+    return {
+      from: this.actorID,
+      input: input,
+      result: resultGrip,
+      timestamp: timestamp,
+      exception: errorGrip,
+      exceptionMessage: this._createStringGrip(errorMessage),
+      exceptionDocURL: errorDocURL,
+      frame,
+      helperResult: helperResult,
+    };
+  },
+
+  /**
+   * The Autocomplete request handler.
+   *
+   * @param object aRequest
+   *        The request message - what input to autocomplete.
+   * @return object
+   *         The response message - matched properties.
+   */
+  onAutocomplete: function WCA_onAutocomplete(aRequest)
+  {
+    let frameActorId = aRequest.frameActor;
+    let dbgObject = null;
+    let environment = null;
+    let hadDebuggee = false;
+
+    // This is the case of the paused debugger
+    if (frameActorId) {
+      let frameActor = this.conn.getActor(frameActorId);
+      try {
+        // Need to try/catch since accessing frame.environment
+        // can throw "Debugger.Frame is not live"
+        let frame = frameActor.frame;
+        environment = frame.environment;
+      } catch (e) {
+        DevToolsUtils.reportException("onAutocomplete",
+          Error("The frame actor was not found: " + frameActorId));
+      }
+    }
+    // This is the general case (non-paused debugger)
+    else {
+      hadDebuggee = this.dbg.hasDebuggee(this.evalWindow);
+      dbgObject = this.dbg.addDebuggee(this.evalWindow);
+    }
+
+    let result = JSPropertyProvider(dbgObject, environment, aRequest.text,
+                                    aRequest.cursor, frameActorId) || {};
+
+    if (!hadDebuggee && dbgObject) {
+      this.dbg.removeDebuggee(this.evalWindow);
+    }
+
+    let matches = result.matches || [];
+    let reqText = aRequest.text.substr(0, aRequest.cursor);
+
+    // We consider '$' as alphanumerc because it is used in the names of some
+    // helper functions.
+    let lastNonAlphaIsDot = /[.][a-zA-Z0-9$]*$/.test(reqText);
+    if (!lastNonAlphaIsDot) {
+      if (!this._webConsoleCommandsCache) {
+        let helpers = {
+          sandbox: Object.create(null)
+        };
+        addWebConsoleCommands(helpers);
+        this._webConsoleCommandsCache =
+          Object.getOwnPropertyNames(helpers.sandbox);
+      }
+      matches = matches.concat(this._webConsoleCommandsCache
+          .filter(n => n.startsWith(result.matchProp)));
+    }
+
+    return {
+      from: this.actorID,
+      matches: matches.sort(),
+      matchProp: result.matchProp,
+    };
+  },
+
+  /**
+   * The "clearMessagesCache" request handler.
+   */
+  onClearMessagesCache: function WCA_onClearMessagesCache()
+  {
+    // TODO: Bug 717611 - Web Console clear button does not clear cached errors
+    let windowId = !this.parentActor.isRootActor ?
+                   WebConsoleUtils.getInnerWindowId(this.window) : null;
+    let ConsoleAPIStorage = Cc["@mozilla.org/consoleAPI-storage;1"]
+                              .getService(Ci.nsIConsoleAPIStorage);
+    ConsoleAPIStorage.clearEvents(windowId);
+
+    CONSOLE_WORKER_IDS.forEach((aId) => {
+      ConsoleAPIStorage.clearEvents(aId);
+    });
+
+    if (this.parentActor.isRootActor) {
+      Services.console.logStringMessage(null); // for the Error Console
+      Services.console.reset();
+    }
+    return {};
+  },
+
+  /**
+   * The "getPreferences" request handler.
+   *
+   * @param object aRequest
+   *        The request message - which preferences need to be retrieved.
+   * @return object
+   *         The response message - a { key: value } object map.
+   */
+  onGetPreferences: function WCA_onGetPreferences(aRequest)
+  {
+    let prefs = Object.create(null);
+    for (let key of aRequest.preferences) {
+      prefs[key] = this._prefs[key];
+    }
+    return { preferences: prefs };
+  },
+
+  /**
+   * The "setPreferences" request handler.
+   *
+   * @param object aRequest
+   *        The request message - which preferences need to be updated.
+   */
+  onSetPreferences: function WCA_onSetPreferences(aRequest)
+  {
+    for (let key in aRequest.preferences) {
+      this._prefs[key] = aRequest.preferences[key];
+
+      if (this.networkMonitor) {
+        if (key == "NetworkMonitor.saveRequestAndResponseBodies") {
+          this.networkMonitor.saveRequestAndResponseBodies = this._prefs[key];
+          if (this.networkMonitorChild) {
+            this.networkMonitorChild.saveRequestAndResponseBodies =
+              this._prefs[key];
+          }
+        } else if (key == "NetworkMonitor.throttleData") {
+          this.networkMonitor.throttleData = this._prefs[key];
+          if (this.networkMonitorChild) {
+            this.networkMonitorChild.throttleData = this._prefs[key];
+          }
+        }
+      }
+    }
+    return { updated: Object.keys(aRequest.preferences) };
+  },
+
+  // End of request handlers.
+
+  /**
+   * Create an object with the API we expose to the Web Console during
+   * JavaScript evaluation.
+   * This object inherits properties and methods from the Web Console actor.
+   *
+   * @private
+   * @param object aDebuggerGlobal
+   *        A Debugger.Object that wraps a content global. This is used for the
+   *        Web Console Commands.
+   * @return object
+   *         The same object as |this|, but with an added |sandbox| property.
+   *         The sandbox holds methods and properties that can be used as
+   *         bindings during JS evaluation.
+   */
+  _getWebConsoleCommands: function (aDebuggerGlobal)
+  {
+    let helpers = {
+      window: this.evalWindow,
+      chromeWindow: this.chromeWindow.bind(this),
+      makeDebuggeeValue: aDebuggerGlobal.makeDebuggeeValue.bind(aDebuggerGlobal),
+      createValueGrip: this.createValueGrip.bind(this),
+      sandbox: Object.create(null),
+      helperResult: null,
+      consoleActor: this,
+    };
+    addWebConsoleCommands(helpers);
+
+    let evalWindow = this.evalWindow;
+    function maybeExport(obj, name) {
+      if (typeof obj[name] != "function") {
+        return;
+      }
+
+      // By default, chrome-implemented functions that are exposed to content
+      // refuse to accept arguments that are cross-origin for the caller. This
+      // is generally the safe thing, but causes problems for certain console
+      // helpers like cd(), where we users sometimes want to pass a cross-origin
+      // window. To circumvent this restriction, we use exportFunction along
+      // with a special option designed for this purpose. See bug 1051224.
+      obj[name] =
+        Cu.exportFunction(obj[name], evalWindow, { allowCrossOriginArguments: true });
+    }
+    for (let name in helpers.sandbox) {
+      let desc = Object.getOwnPropertyDescriptor(helpers.sandbox, name);
+
+      // Workers don't have access to Cu so won't be able to exportFunction.
+      if (!isWorker) {
+        maybeExport(desc, "get");
+        maybeExport(desc, "set");
+        maybeExport(desc, "value");
+      }
+      if (desc.value) {
+        // Make sure the helpers can be used during eval.
+        desc.value = aDebuggerGlobal.makeDebuggeeValue(desc.value);
+      }
+      Object.defineProperty(helpers.sandbox, name, desc);
+    }
+    return helpers;
+  },
+
+  /**
+   * Evaluates a string using the debugger API.
+   *
+   * To allow the variables view to update properties from the Web Console we
+   * provide the "bindObjectActor" mechanism: the Web Console tells the
+   * ObjectActor ID for which it desires to evaluate an expression. The
+   * Debugger.Object pointed at by the actor ID is bound such that it is
+   * available during expression evaluation (executeInGlobalWithBindings()).
+   *
+   * Example:
+   *   _self['foobar'] = 'test'
+   * where |_self| refers to the desired object.
+   *
+   * The |frameActor| property allows the Web Console client to provide the
+   * frame actor ID, such that the expression can be evaluated in the
+   * user-selected stack frame.
+   *
+   * For the above to work we need the debugger and the Web Console to share
+   * a connection, otherwise the Web Console actor will not find the frame
+   * actor.
+   *
+   * The Debugger.Frame comes from the jsdebugger's Debugger instance, which
+   * is different from the Web Console's Debugger instance. This means that
+   * for evaluation to work, we need to create a new instance for the Web
+   * Console Commands helpers - they need to be Debugger.Objects coming from the
+   * jsdebugger's Debugger instance.
+   *
+   * When |bindObjectActor| is used objects can come from different iframes,
+   * from different domains. To avoid permission-related errors when objects
+   * come from a different window, we also determine the object's own global,
+   * such that evaluation happens in the context of that global. This means that
+   * evaluation will happen in the object's iframe, rather than the top level
+   * window.
+   *
+   * @param string aString
+   *        String to evaluate.
+   * @param object [aOptions]
+   *        Options for evaluation:
+   *        - bindObjectActor: the ObjectActor ID to use for evaluation.
+   *          |evalWithBindings()| will be called with one additional binding:
+   *          |_self| which will point to the Debugger.Object of the given
+   *          ObjectActor.
+   *        - selectedObjectActor: Like bindObjectActor, but executes with the
+   *          top level window as the global.
+   *        - frameActor: the FrameActor ID to use for evaluation. The given
+   *        debugger frame is used for evaluation, instead of the global window.
+   *        - selectedNodeActor: the NodeActor ID of the currently selected node
+   *        in the Inspector (or null, if there is no selection). This is used
+   *        for helper functions that make reference to the currently selected
+   *        node, like $0.
+   *         - url: the url to evaluate the script as. Defaults to
+   *         "debugger eval code".
+   * @return object
+   *         An object that holds the following properties:
+   *         - dbg: the debugger where the string was evaluated.
+   *         - frame: (optional) the frame where the string was evaluated.
+   *         - window: the Debugger.Object for the global where the string was
+   *         evaluated.
+   *         - result: the result of the evaluation.
+   *         - helperResult: any result coming from a Web Console commands
+   *         function.
+   */
+  evalWithDebugger: function WCA_evalWithDebugger(aString, aOptions = {})
+  {
+    let trimmedString = aString.trim();
+    // The help function needs to be easy to guess, so we make the () optional.
+    if (trimmedString == "help" || trimmedString == "?") {
+      aString = "help()";
+    }
+
+    // Add easter egg for console.mihai().
+    if (trimmedString == "console.mihai()" || trimmedString == "console.mihai();") {
+      aString = "\"http://incompleteness.me/blog/2015/02/09/console-dot-mihai/\"";
+    }
+
+    // Find the Debugger.Frame of the given FrameActor.
+    let frame = null, frameActor = null;
+    if (aOptions.frameActor) {
+      frameActor = this.conn.getActor(aOptions.frameActor);
+      if (frameActor) {
+        frame = frameActor.frame;
+      }
+      else {
+        DevToolsUtils.reportException("evalWithDebugger",
+          Error("The frame actor was not found: " + aOptions.frameActor));
+      }
+    }
+
+    // If we've been given a frame actor in whose scope we should evaluate the
+    // expression, be sure to use that frame's Debugger (that is, the JavaScript
+    // debugger's Debugger) for the whole operation, not the console's Debugger.
+    // (One Debugger will treat a different Debugger's Debugger.Object instances
+    // as ordinary objects, not as references to be followed, so mixing
+    // debuggers causes strange behaviors.)
+    let dbg = frame ? frameActor.threadActor.dbg : this.dbg;
+    let dbgWindow = dbg.makeGlobalObjectReference(this.evalWindow);
+
+    // If we have an object to bind to |_self|, create a Debugger.Object
+    // referring to that object, belonging to dbg.
+    let bindSelf = null;
+    if (aOptions.bindObjectActor || aOptions.selectedObjectActor) {
+      let objActor = this.getActorByID(aOptions.bindObjectActor ||
+                                       aOptions.selectedObjectActor);
+      if (objActor) {
+        let jsObj = objActor.obj.unsafeDereference();
+        // If we use the makeDebuggeeValue method of jsObj's own global, then
+        // we'll get a D.O that sees jsObj as viewed from its own compartment -
+        // that is, without wrappers. The evalWithBindings call will then wrap
+        // jsObj appropriately for the evaluation compartment.
+        let global = Cu.getGlobalForObject(jsObj);
+        let _dbgWindow = dbg.makeGlobalObjectReference(global);
+        bindSelf = dbgWindow.makeDebuggeeValue(jsObj);
+
+        if (aOptions.bindObjectActor) {
+          dbgWindow = _dbgWindow;
+        }
+      }
+    }
+
+    // Get the Web Console commands for the given debugger window.
+    let helpers = this._getWebConsoleCommands(dbgWindow);
+    let bindings = helpers.sandbox;
+    if (bindSelf) {
+      bindings._self = bindSelf;
+    }
+
+    if (aOptions.selectedNodeActor) {
+      let actor = this.conn.getActor(aOptions.selectedNodeActor);
+      if (actor) {
+        helpers.selectedNode = actor.rawNode;
+      }
+    }
+
+    // Check if the Debugger.Frame or Debugger.Object for the global include
+    // $ or $$. We will not overwrite these functions with the Web Console
+    // commands.
+    let found$ = false, found$$ = false;
+    if (frame) {
+      let env = frame.environment;
+      if (env) {
+        found$ = !!env.find("$");
+        found$$ = !!env.find("$$");
+      }
+    }
+    else {
+      found$ = !!dbgWindow.getOwnPropertyDescriptor("$");
+      found$$ = !!dbgWindow.getOwnPropertyDescriptor("$$");
+    }
+
+    let $ = null, $$ = null;
+    if (found$) {
+      $ = bindings.$;
+      delete bindings.$;
+    }
+    if (found$$) {
+      $$ = bindings.$$;
+      delete bindings.$$;
+    }
+
+    // Ready to evaluate the string.
+    helpers.evalInput = aString;
+
+    let evalOptions;
+    if (typeof aOptions.url == "string") {
+      evalOptions = { url: aOptions.url };
+    }
+
+    // If the debugger object is changed from the last evaluation,
+    // adopt this._lastConsoleInputEvaluation value in the new debugger,
+    // to prevents "Debugger.Object belongs to a different Debugger" exceptions
+    // related to the $_ bindings.
+    if (this._lastConsoleInputEvaluation &&
+        this._lastConsoleInputEvaluation.global !== dbgWindow) {
+      this._lastConsoleInputEvaluation = dbg.adoptDebuggeeValue(
+        this._lastConsoleInputEvaluation
+      );
+    }
+
+    let result;
+
+    if (frame) {
+      result = frame.evalWithBindings(aString, bindings, evalOptions);
+    }
+    else {
+      result = dbgWindow.executeInGlobalWithBindings(aString, bindings, evalOptions);
+      // Attempt to initialize any declarations found in the evaluated string
+      // since they may now be stuck in an "initializing" state due to the
+      // error. Already-initialized bindings will be ignored.
+      if ("throw" in result) {
+        let ast;
+        // Parse errors will raise an exception. We can/should ignore the error
+        // since it's already being handled elsewhere and we are only interested
+        // in initializing bindings.
+        try {
+          ast = Parser.reflectionAPI.parse(aString);
+        } catch (ex) {
+          ast = {"body": []};
+        }
+        for (let line of ast.body) {
+          // Only let and const declarations put bindings into an
+          // "initializing" state.
+          if (!(line.kind == "let" || line.kind == "const"))
+            continue;
+
+          let identifiers = [];
+          for (let decl of line.declarations) {
+            switch (decl.id.type) {
+              case "Identifier":
+                // let foo = bar;
+                identifiers.push(decl.id.name);
+                break;
+              case "ArrayPattern":
+                // let [foo, bar]    = [1, 2];
+                // let [foo=99, bar] = [1, 2];
+                for (let e of decl.id.elements) {
+                  if (e.type == "Identifier") {
+                    identifiers.push(e.name);
+                  } else if (e.type == "AssignmentExpression") {
+                    identifiers.push(e.left.name);
+                  }
+                }
+                break;
+              case "ObjectPattern":
+                // let {bilbo, my}    = {bilbo: "baggins", my: "precious"};
+                // let {blah: foo}    = {blah: yabba()}
+                // let {blah: foo=99} = {blah: yabba()}
+                for (let prop of decl.id.properties) {
+                  // key
+                  if (prop.key.type == "Identifier")
+                    identifiers.push(prop.key.name);
+                  // value
+                  if (prop.value.type == "Identifier") {
+                    identifiers.push(prop.value.name);
+                  } else if (prop.value.type == "AssignmentExpression") {
+                    identifiers.push(prop.value.left.name);
+                  }
+                }
+                break;
+            }
+          }
+
+          for (let name of identifiers)
+            dbgWindow.forceLexicalInitializationByName(name);
+        }
+      }
+    }
+
+    let helperResult = helpers.helperResult;
+    delete helpers.evalInput;
+    delete helpers.helperResult;
+    delete helpers.selectedNode;
+
+    if ($) {
+      bindings.$ = $;
+    }
+    if ($$) {
+      bindings.$$ = $$;
+    }
+
+    if (bindings._self) {
+      delete bindings._self;
+    }
+
+    return {
+      result: result,
+      helperResult: helperResult,
+      dbg: dbg,
+      frame: frame,
+      window: dbgWindow,
+    };
+  },
+
+  // Event handlers for various listeners.
+
+  /**
+   * Handler for messages received from the ConsoleServiceListener. This method
+   * sends the nsIConsoleMessage to the remote Web Console client.
+   *
+   * @param nsIConsoleMessage aMessage
+   *        The message we need to send to the client.
+   */
+  onConsoleServiceMessage: function WCA_onConsoleServiceMessage(aMessage)
+  {
+    let packet;
+    if (aMessage instanceof Ci.nsIScriptError) {
+      packet = {
+        from: this.actorID,
+        type: "pageError",
+        pageError: this.preparePageErrorForRemote(aMessage),
+      };
+    }
+    else {
+      packet = {
+        from: this.actorID,
+        type: "logMessage",
+        message: this._createStringGrip(aMessage.message),
+        timeStamp: aMessage.timeStamp,
+      };
+    }
+    this.conn.send(packet);
+  },
+
+  /**
+   * Prepare an nsIScriptError to be sent to the client.
+   *
+   * @param nsIScriptError aPageError
+   *        The page error we need to send to the client.
+   * @return object
+   *         The object you can send to the remote client.
+   */
+  preparePageErrorForRemote: function WCA_preparePageErrorForRemote(aPageError)
+  {
+    let stack = null;
+    // Convert stack objects to the JSON attributes expected by client code
+    if (aPageError.stack) {
+      stack = [];
+      let s = aPageError.stack;
+      while (s !== null) {
+        stack.push({
+          filename: s.source,
+          lineNumber: s.line,
+          columnNumber: s.column,
+          functionName: s.functionDisplayName
+        });
+        s = s.parent;
+      }
+    }
+    let lineText = aPageError.sourceLine;
+    if (lineText && lineText.length > DebuggerServer.LONG_STRING_INITIAL_LENGTH) {
+      lineText = lineText.substr(0, DebuggerServer.LONG_STRING_INITIAL_LENGTH);
+    }
+
+    return {
+      errorMessage: this._createStringGrip(aPageError.errorMessage),
+      errorMessageName: aPageError.errorMessageName,
+      exceptionDocURL: ErrorDocs.GetURL(aPageError),
+      sourceName: aPageError.sourceName,
+      lineText: lineText,
+      lineNumber: aPageError.lineNumber,
+      columnNumber: aPageError.columnNumber,
+      category: aPageError.category,
+      timeStamp: aPageError.timeStamp,
+      warning: !!(aPageError.flags & aPageError.warningFlag),
+      error: !!(aPageError.flags & aPageError.errorFlag),
+      exception: !!(aPageError.flags & aPageError.exceptionFlag),
+      strict: !!(aPageError.flags & aPageError.strictFlag),
+      info: !!(aPageError.flags & aPageError.infoFlag),
+      private: aPageError.isFromPrivateWindow,
+      stacktrace: stack
+    };
+  },
+
+  /**
+   * Handler for window.console API calls received from the ConsoleAPIListener.
+   * This method sends the object to the remote Web Console client.
+   *
+   * @see ConsoleAPIListener
+   * @param object aMessage
+   *        The console API call we need to send to the remote client.
+   */
+  onConsoleAPICall: function WCA_onConsoleAPICall(aMessage)
+  {
+    let packet = {
+      from: this.actorID,
+      type: "consoleAPICall",
+      message: this.prepareConsoleMessageForRemote(aMessage),
+    };
+    this.conn.send(packet);
+  },
+
+  /**
+   * Handler for network events. This method is invoked when a new network event
+   * is about to be recorded.
+   *
+   * @see NetworkEventActor
+   * @see NetworkMonitor from webconsole/utils.js
+   *
+   * @param object aEvent
+   *        The initial network request event information.
+   * @return object
+   *         A new NetworkEventActor is returned. This is used for tracking the
+   *         network request and response.
+   */
+  onNetworkEvent: function WCA_onNetworkEvent(aEvent)
+  {
+    let actor = this.getNetworkEventActor(aEvent.channelId);
+    actor.init(aEvent);
+
+    let packet = {
+      from: this.actorID,
+      type: "networkEvent",
+      eventActor: actor.grip()
+    };
+
+    this.conn.send(packet);
+
+    return actor;
+  },
+
+  /**
+   * Get the NetworkEventActor for a nsIHttpChannel, if it exists,
+   * otherwise create a new one.
+   *
+   * @param string channelId
+   *        The id of the channel for the network event.
+   * @return object
+   *         The NetworkEventActor for the given channel.
+   */
+  getNetworkEventActor: function WCA_getNetworkEventActor(channelId) {
+    let actor = this._netEvents.get(channelId);
+    if (actor) {
+      // delete from map as we should only need to do this check once
+      this._netEvents.delete(channelId);
+      return actor;
+    }
+
+    actor = new NetworkEventActor(this);
+    this._actorPool.addActor(actor);
+    return actor;
+  },
+
+  /**
+   * Send a new HTTP request from the target's window.
+   *
+   * @param object message
+   *        Object with 'request' - the HTTP request details.
+   */
+  onSendHTTPRequest(message) {
+    let { url, method, headers, body } = message.request;
+
+    // Set the loadingNode and loadGroup to the target document - otherwise the
+    // request won't show up in the opened netmonitor.
+    let doc = this.window.document;
+
+    let channel = NetUtil.newChannel({
+      uri: NetUtil.newURI(url),
+      loadingNode: doc,
+      securityFlags: Ci.nsILoadInfo.SEC_ALLOW_CROSS_ORIGIN_DATA_IS_NULL,
+      contentPolicyType: Ci.nsIContentPolicy.TYPE_OTHER
+    });
+
+    channel.QueryInterface(Ci.nsIHttpChannel);
+
+    channel.loadGroup = doc.documentLoadGroup;
+    channel.loadFlags |= Ci.nsIRequest.LOAD_BYPASS_CACHE |
+                         Ci.nsIRequest.INHIBIT_CACHING |
+                         Ci.nsIRequest.LOAD_ANONYMOUS;
+
+    channel.requestMethod = method;
+
+    for (let {name, value} of headers) {
+      channel.setRequestHeader(name, value, false);
+    }
+
+    if (body) {
+      channel.QueryInterface(Ci.nsIUploadChannel2);
+      let bodyStream = Cc["@mozilla.org/io/string-input-stream;1"]
+        .createInstance(Ci.nsIStringInputStream);
+      bodyStream.setData(body, body.length);
+      channel.explicitSetUploadStream(bodyStream, null, -1, method, false);
+    }
+
+    NetUtil.asyncFetch(channel, () => {});
+
+    let actor = this.getNetworkEventActor(channel.channelId);
+
+    // map channel to actor so we can associate future events with it
+    this._netEvents.set(channel.channelId, actor);
+
+    return {
+      from: this.actorID,
+      eventActor: actor.grip()
+    };
+  },
+
+  /**
+   * Handler for file activity. This method sends the file request information
+   * to the remote Web Console client.
+   *
+   * @see ConsoleProgressListener
+   * @param string aFileURI
+   *        The requested file URI.
+   */
+  onFileActivity: function WCA_onFileActivity(aFileURI)
+  {
+    let packet = {
+      from: this.actorID,
+      type: "fileActivity",
+      uri: aFileURI,
+    };
+    this.conn.send(packet);
+  },
+
+  /**
+   * Handler for reflow activity. This method forwards reflow events to the
+   * remote Web Console client.
+   *
+   * @see ConsoleReflowListener
+   * @param Object aReflowInfo
+   */
+  onReflowActivity: function WCA_onReflowActivity(aReflowInfo)
+  {
+    let packet = {
+      from: this.actorID,
+      type: "reflowActivity",
+      interruptible: aReflowInfo.interruptible,
+      start: aReflowInfo.start,
+      end: aReflowInfo.end,
+      sourceURL: aReflowInfo.sourceURL,
+      sourceLine: aReflowInfo.sourceLine,
+      functionName: aReflowInfo.functionName
+    };
+
+    this.conn.send(packet);
+  },
+
+  /**
+   * Handler for server logging. This method forwards log events to the
+   * remote Web Console client.
+   *
+   * @see ServerLoggingListener
+   * @param object aMessage
+   *        The console API call on the server we need to send to the remote client.
+   */
+  onServerLogCall: function WCA_onServerLogCall(aMessage)
+  {
+    // Clone all data into the content scope (that's where
+    // passed arguments comes from).
+    let msg = Cu.cloneInto(aMessage, this.window);
+
+    // All arguments within the message need to be converted into
+    // debuggees to properly send it to the client side.
+    // Use the default target: this.window as the global object
+    // since that's the correct scope for data in the message.
+    // The 'false' argument passed into prepareConsoleMessageForRemote()
+    // ensures that makeDebuggeeValue uses content debuggee.
+    // See also:
+    // * makeDebuggeeValue()
+    // * prepareConsoleMessageForRemote()
+    msg = this.prepareConsoleMessageForRemote(msg, false);
+
+    let packet = {
+      from: this.actorID,
+      type: "serverLogCall",
+      message: msg,
+    };
+
+    this.conn.send(packet);
+  },
+
+  // End of event handlers for various listeners.
+
+  /**
+   * Prepare a message from the console API to be sent to the remote Web Console
+   * instance.
+   *
+   * @param object aMessage
+   *        The original message received from console-api-log-event.
+   * @param boolean aUseObjectGlobal
+   *        If |true| the object global is determined and added as a debuggee,
+   *        otherwise |this.window| is used when makeDebuggeeValue() is invoked.
+   * @return object
+   *         The object that can be sent to the remote client.
+   */
+  prepareConsoleMessageForRemote:
+  function WCA_prepareConsoleMessageForRemote(aMessage, aUseObjectGlobal = true)
+  {
+    let result = WebConsoleUtils.cloneObject(aMessage);
+
+    result.workerType = WebConsoleUtils.getWorkerType(result) || "none";
+
+    delete result.wrappedJSObject;
+    delete result.ID;
+    delete result.innerID;
+    delete result.consoleID;
+
+    result.arguments = Array.map(aMessage.arguments || [], (aObj) => {
+      let dbgObj = this.makeDebuggeeValue(aObj, aUseObjectGlobal);
+      return this.createValueGrip(dbgObj);
+    });
+
+    result.styles = Array.map(aMessage.styles || [], (aString) => {
+      return this.createValueGrip(aString);
+    });
+
+    result.category = aMessage.category || "webdev";
+
+    return result;
+  },
+
+  /**
+   * Find the XUL window that owns the content window.
+   *
+   * @return Window
+   *         The XUL window that owns the content window.
+   */
+  chromeWindow: function WCA_chromeWindow()
+  {
+    let window = null;
+    try {
+      window = this.window.QueryInterface(Ci.nsIInterfaceRequestor)
+             .getInterface(Ci.nsIWebNavigation).QueryInterface(Ci.nsIDocShell)
+             .chromeEventHandler.ownerDocument.defaultView;
+    }
+    catch (ex) {
+      // The above can fail because chromeEventHandler is not available for all
+      // kinds of |this.window|.
+    }
+
+    return window;
+  },
+
+  /**
+   * Notification observer for the "last-pb-context-exited" topic.
+   *
+   * @private
+   * @param object aSubject
+   *        Notification subject - in this case it is the inner window ID that
+   *        was destroyed.
+   * @param string aTopic
+   *        Notification topic.
+   */
+  _onObserverNotification: function WCA__onObserverNotification(aSubject, aTopic)
+  {
+    switch (aTopic) {
+      case "last-pb-context-exited":
+        this.conn.send({
+          from: this.actorID,
+          type: "lastPrivateContextExited",
+        });
+        break;
+    }
+  },
+
+  /**
+   * The "will-navigate" progress listener. This is used to clear the current
+   * eval scope.
+   */
+  _onWillNavigate: function WCA__onWillNavigate({ window, isTopLevel })
+  {
+    if (isTopLevel) {
+      this._evalWindow = null;
+      events.off(this.parentActor, "will-navigate", this._onWillNavigate);
+      this._progressListenerActive = false;
+    }
+  },
+
+  /**
+   * This listener is called when we switch to another frame,
+   * mostly to unregister previous listeners and start listening on the new document.
+   */
+  _onChangedToplevelDocument: function WCA__onChangedToplevelDocument()
+  {
+    // Convert the Set to an Array
+    let listeners = [...this._listeners];
+
+    // Unregister existing listener on the previous document
+    // (pass a copy of the array as it will shift from it)
+    this.onStopListeners({listeners: listeners.slice()});
+
+    // This method is called after this.window is changed,
+    // so we register new listener on this new window
+    this.onStartListeners({listeners: listeners});
+
+    // Also reset the cached top level chrome window being targeted
+    this._lastChromeWindow = null;
+  },
+};
+
+WebConsoleActor.prototype.requestTypes =
+{
+  startListeners: WebConsoleActor.prototype.onStartListeners,
+  stopListeners: WebConsoleActor.prototype.onStopListeners,
+  getCachedMessages: WebConsoleActor.prototype.onGetCachedMessages,
+  evaluateJS: WebConsoleActor.prototype.onEvaluateJS,
+  evaluateJSAsync: WebConsoleActor.prototype.onEvaluateJSAsync,
+  autocomplete: WebConsoleActor.prototype.onAutocomplete,
+  clearMessagesCache: WebConsoleActor.prototype.onClearMessagesCache,
+  getPreferences: WebConsoleActor.prototype.onGetPreferences,
+  setPreferences: WebConsoleActor.prototype.onSetPreferences,
+  sendHTTPRequest: WebConsoleActor.prototype.onSendHTTPRequest
+};
+
+exports.WebConsoleActor = WebConsoleActor;
+
+/**
+ * Creates an actor for a network event.
+ *
+ * @constructor
+ * @param object webConsoleActor
+ *        The parent WebConsoleActor instance for this object.
+ */
+function NetworkEventActor(webConsoleActor) {
+  this.parent = webConsoleActor;
+  this.conn = this.parent.conn;
+
+  this._request = {
+    method: null,
+    url: null,
+    httpVersion: null,
+    headers: [],
+    cookies: [],
+    headersSize: null,
+    postData: {},
+  };
+
+  this._response = {
+    headers: [],
+    cookies: [],
+    content: {},
+  };
+
+  this._timings = {};
+
+  // Keep track of LongStringActors owned by this NetworkEventActor.
+  this._longStringActors = new Set();
+}
+
+NetworkEventActor.prototype =
+{
+  _request: null,
+  _response: null,
+  _timings: null,
+  _longStringActors: null,
+
+  actorPrefix: "netEvent",
+
+  /**
+   * Returns a grip for this actor for returning in a protocol message.
+   */
+  grip: function NEA_grip()
+  {
+    return {
+      actor: this.actorID,
+      startedDateTime: this._startedDateTime,
+      timeStamp: Date.parse(this._startedDateTime),
+      url: this._request.url,
+      method: this._request.method,
+      isXHR: this._isXHR,
+      cause: this._cause,
+      fromCache: this._fromCache,
+      fromServiceWorker: this._fromServiceWorker,
+      private: this._private,
+    };
+  },
+
+  /**
+   * Releases this actor from the pool.
+   */
+  release: function NEA_release()
+  {
+    for (let grip of this._longStringActors) {
+      let actor = this.parent.getActorByID(grip.actor);
+      if (actor) {
+        this.parent.releaseActor(actor);
+      }
+    }
+    this._longStringActors = new Set();
+
+    if (this.channel) {
+      this.parent._netEvents.delete(this.channel);
+    }
+    this.parent.releaseActor(this);
+  },
+
+  /**
+   * Handle a protocol request to release a grip.
+   */
+  onRelease: function NEA_onRelease()
+  {
+    this.release();
+    return {};
+  },
+
+  /**
+   * Set the properties of this actor based on it's corresponding
+   * network event.
+   *
+   * @param object aNetworkEvent
+   *        The network event associated with this actor.
+   */
+  init: function NEA_init(aNetworkEvent)
+  {
+    this._startedDateTime = aNetworkEvent.startedDateTime;
+    this._isXHR = aNetworkEvent.isXHR;
+    this._cause = aNetworkEvent.cause;
+    this._fromCache = aNetworkEvent.fromCache;
+    this._fromServiceWorker = aNetworkEvent.fromServiceWorker;
+
+    for (let prop of ["method", "url", "httpVersion", "headersSize"]) {
+      this._request[prop] = aNetworkEvent[prop];
+    }
+
+    this._discardRequestBody = aNetworkEvent.discardRequestBody;
+    this._discardResponseBody = aNetworkEvent.discardResponseBody;
+    this._private = aNetworkEvent.private;
+  },
+
+  /**
+   * The "getRequestHeaders" packet type handler.
+   *
+   * @return object
+   *         The response packet - network request headers.
+   */
+  onGetRequestHeaders: function NEA_onGetRequestHeaders()
+  {
+    return {
+      from: this.actorID,
+      headers: this._request.headers,
+      headersSize: this._request.headersSize,
+      rawHeaders: this._request.rawHeaders,
+    };
+  },
+
+  /**
+   * The "getRequestCookies" packet type handler.
+   *
+   * @return object
+   *         The response packet - network request cookies.
+   */
+  onGetRequestCookies: function NEA_onGetRequestCookies()
+  {
+    return {
+      from: this.actorID,
+      cookies: this._request.cookies,
+    };
+  },
+
+  /**
+   * The "getRequestPostData" packet type handler.
+   *
+   * @return object
+   *         The response packet - network POST data.
+   */
+  onGetRequestPostData: function NEA_onGetRequestPostData()
+  {
+    return {
+      from: this.actorID,
+      postData: this._request.postData,
+      postDataDiscarded: this._discardRequestBody,
+    };
+  },
+
+  /**
+   * The "getSecurityInfo" packet type handler.
+   *
+   * @return object
+   *         The response packet - connection security information.
+   */
+  onGetSecurityInfo: function NEA_onGetSecurityInfo()
+  {
+    return {
+      from: this.actorID,
+      securityInfo: this._securityInfo,
+    };
+  },
+
+  /**
+   * The "getResponseHeaders" packet type handler.
+   *
+   * @return object
+   *         The response packet - network response headers.
+   */
+  onGetResponseHeaders: function NEA_onGetResponseHeaders()
+  {
+    return {
+      from: this.actorID,
+      headers: this._response.headers,
+      headersSize: this._response.headersSize,
+      rawHeaders: this._response.rawHeaders,
+    };
+  },
+
+  /**
+   * The "getResponseCookies" packet type handler.
+   *
+   * @return object
+   *         The response packet - network response cookies.
+   */
+  onGetResponseCookies: function NEA_onGetResponseCookies()
+  {
+    return {
+      from: this.actorID,
+      cookies: this._response.cookies,
+    };
+  },
+
+  /**
+   * The "getResponseContent" packet type handler.
+   *
+   * @return object
+   *         The response packet - network response content.
+   */
+  onGetResponseContent: function NEA_onGetResponseContent()
+  {
+    return {
+      from: this.actorID,
+      content: this._response.content,
+      contentDiscarded: this._discardResponseBody,
+    };
+  },
+
+  /**
+   * The "getEventTimings" packet type handler.
+   *
+   * @return object
+   *         The response packet - network event timings.
+   */
+  onGetEventTimings: function NEA_onGetEventTimings()
+  {
+    return {
+      from: this.actorID,
+      timings: this._timings,
+      totalTime: this._totalTime
+    };
+  },
+
+  /** ****************************************************************
+   * Listeners for new network event data coming from NetworkMonitor.
+   ******************************************************************/
+
+  /**
+   * Add network request headers.
+   *
+   * @param array aHeaders
+   *        The request headers array.
+   * @param string aRawHeaders
+   *        The raw headers source.
+   */
+  addRequestHeaders: function NEA_addRequestHeaders(aHeaders, aRawHeaders)
+  {
+    this._request.headers = aHeaders;
+    this._prepareHeaders(aHeaders);
+
+    var rawHeaders = this.parent._createStringGrip(aRawHeaders);
+    if (typeof rawHeaders == "object") {
+      this._longStringActors.add(rawHeaders);
+    }
+    this._request.rawHeaders = rawHeaders;
+
+    let packet = {
+      from: this.actorID,
+      type: "networkEventUpdate",
+      updateType: "requestHeaders",
+      headers: aHeaders.length,
+      headersSize: this._request.headersSize,
+    };
+
+    this.conn.send(packet);
+  },
+
+  /**
+   * Add network request cookies.
+   *
+   * @param array aCookies
+   *        The request cookies array.
+   */
+  addRequestCookies: function NEA_addRequestCookies(aCookies)
+  {
+    this._request.cookies = aCookies;
+    this._prepareHeaders(aCookies);
+
+    let packet = {
+      from: this.actorID,
+      type: "networkEventUpdate",
+      updateType: "requestCookies",
+      cookies: aCookies.length,
+    };
+
+    this.conn.send(packet);
+  },
+
+  /**
+   * Add network request POST data.
+   *
+   * @param object aPostData
+   *        The request POST data.
+   */
+  addRequestPostData: function NEA_addRequestPostData(aPostData)
+  {
+    this._request.postData = aPostData;
+    aPostData.text = this.parent._createStringGrip(aPostData.text);
+    if (typeof aPostData.text == "object") {
+      this._longStringActors.add(aPostData.text);
+    }
+
+    let packet = {
+      from: this.actorID,
+      type: "networkEventUpdate",
+      updateType: "requestPostData",
+      dataSize: aPostData.text.length,
+      discardRequestBody: this._discardRequestBody,
+    };
+
+    this.conn.send(packet);
+  },
+
+  /**
+   * Add the initial network response information.
+   *
+   * @param object aInfo
+   *        The response information.
+   * @param string aRawHeaders
+   *        The raw headers source.
+   */
+  addResponseStart: function NEA_addResponseStart(aInfo, aRawHeaders)
+  {
+    var rawHeaders = this.parent._createStringGrip(aRawHeaders);
+    if (typeof rawHeaders == "object") {
+      this._longStringActors.add(rawHeaders);
+    }
+    this._response.rawHeaders = rawHeaders;
+
+    this._response.httpVersion = aInfo.httpVersion;
+    this._response.status = aInfo.status;
+    this._response.statusText = aInfo.statusText;
+    this._response.headersSize = aInfo.headersSize;
+    this._discardResponseBody = aInfo.discardResponseBody;
+
+    let packet = {
+      from: this.actorID,
+      type: "networkEventUpdate",
+      updateType: "responseStart",
+      response: aInfo
+    };
+
+    this.conn.send(packet);
+  },
+
+  /**
+   * Add connection security information.
+   *
+   * @param object info
+   *        The object containing security information.
+   */
+  addSecurityInfo: function NEA_addSecurityInfo(info)
+  {
+    this._securityInfo = info;
+
+    let packet = {
+      from: this.actorID,
+      type: "networkEventUpdate",
+      updateType: "securityInfo",
+      state: info.state,
+    };
+
+    this.conn.send(packet);
+  },
+
+  /**
+   * Add network response headers.
+   *
+   * @param array aHeaders
+   *        The response headers array.
+   */
+  addResponseHeaders: function NEA_addResponseHeaders(aHeaders)
+  {
+    this._response.headers = aHeaders;
+    this._prepareHeaders(aHeaders);
+
+    let packet = {
+      from: this.actorID,
+      type: "networkEventUpdate",
+      updateType: "responseHeaders",
+      headers: aHeaders.length,
+      headersSize: this._response.headersSize,
+    };
+
+    this.conn.send(packet);
+  },
+
+  /**
+   * Add network response cookies.
+   *
+   * @param array aCookies
+   *        The response cookies array.
+   */
+  addResponseCookies: function NEA_addResponseCookies(aCookies)
+  {
+    this._response.cookies = aCookies;
+    this._prepareHeaders(aCookies);
+
+    let packet = {
+      from: this.actorID,
+      type: "networkEventUpdate",
+      updateType: "responseCookies",
+      cookies: aCookies.length,
+    };
+
+    this.conn.send(packet);
+  },
+
+  /**
+   * Add network response content.
+   *
+   * @param object aContent
+   *        The response content.
+   * @param boolean aDiscardedResponseBody
+   *        Tells if the response content was recorded or not.
+   */
+  addResponseContent:
+  function NEA_addResponseContent(aContent, aDiscardedResponseBody)
+  {
+    this._response.content = aContent;
+    aContent.text = this.parent._createStringGrip(aContent.text);
+    if (typeof aContent.text == "object") {
+      this._longStringActors.add(aContent.text);
+    }
+
+    let packet = {
+      from: this.actorID,
+      type: "networkEventUpdate",
+      updateType: "responseContent",
+      mimeType: aContent.mimeType,
+      contentSize: aContent.size,
+      encoding: aContent.encoding,
+      transferredSize: aContent.transferredSize,
+      discardResponseBody: aDiscardedResponseBody,
+    };
+
+    this.conn.send(packet);
+  },
+
+  /**
+   * Add network event timing information.
+   *
+   * @param number aTotal
+   *        The total time of the network event.
+   * @param object aTimings
+   *        Timing details about the network event.
+   */
+  addEventTimings: function NEA_addEventTimings(aTotal, aTimings)
+  {
+    this._totalTime = aTotal;
+    this._timings = aTimings;
+
+    let packet = {
+      from: this.actorID,
+      type: "networkEventUpdate",
+      updateType: "eventTimings",
+      totalTime: aTotal
+    };
+
+    this.conn.send(packet);
+  },
+
+  /**
+   * Prepare the headers array to be sent to the client by using the
+   * LongStringActor for the header values, when needed.
+   *
+   * @private
+   * @param array aHeaders
+   */
+  _prepareHeaders: function NEA__prepareHeaders(aHeaders)
+  {
+    for (let header of aHeaders) {
+      header.value = this.parent._createStringGrip(header.value);
+      if (typeof header.value == "object") {
+        this._longStringActors.add(header.value);
+      }
+    }
+  },
+};
+
+NetworkEventActor.prototype.requestTypes =
+{
+  "release": NetworkEventActor.prototype.onRelease,
+  "getRequestHeaders": NetworkEventActor.prototype.onGetRequestHeaders,
+  "getRequestCookies": NetworkEventActor.prototype.onGetRequestCookies,
+  "getRequestPostData": NetworkEventActor.prototype.onGetRequestPostData,
+  "getResponseHeaders": NetworkEventActor.prototype.onGetResponseHeaders,
+  "getResponseCookies": NetworkEventActor.prototype.onGetResponseCookies,
+  "getResponseContent": NetworkEventActor.prototype.onGetResponseContent,
+  "getEventTimings": NetworkEventActor.prototype.onGetEventTimings,
+  "getSecurityInfo": NetworkEventActor.prototype.onGetSecurityInfo,
+};
diff --git a/devtools/server/actors/webextension.js b/devtools/server/actors/webextension.js
new file mode 100644
index 000000000..0e83fc999
--- /dev/null
+++ b/devtools/server/actors/webextension.js
@@ -0,0 +1,333 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Ci, Cu } = require("chrome");
+const Services = require("Services");
+const { ChromeActor } = require("./chrome");
+const makeDebugger = require("./utils/make-debugger");
+
+var DevToolsUtils = require("devtools/shared/DevToolsUtils");
+var { assert } = DevToolsUtils;
+
+loader.lazyRequireGetter(this, "mapURIToAddonID", "devtools/server/actors/utils/map-uri-to-addon-id");
+loader.lazyRequireGetter(this, "unwrapDebuggerObjectGlobal", "devtools/server/actors/script", true);
+
+loader.lazyImporter(this, "AddonManager", "resource://gre/modules/AddonManager.jsm");
+loader.lazyImporter(this, "XPIProvider", "resource://gre/modules/addons/XPIProvider.jsm");
+
+const FALLBACK_DOC_MESSAGE = "Your addon does not have any document opened yet.";
+
+/**
+ * Creates a TabActor for debugging all the contexts associated to a target WebExtensions
+ * add-on.
+ * Most of the implementation is inherited from ChromeActor (which inherits most of its
+ * implementation from TabActor).
+ * WebExtensionActor is a child of RootActor, it can be retrieved via
+ * RootActor.listAddons request.
+ * WebExtensionActor exposes all tab actors via its form() request, like TabActor.
+ *
+ * History lecture:
+ * The add-on actors used to not inherit TabActor because of the different way the
+ * add-on APIs where exposed to the add-on itself, and for this reason the Addon Debugger
+ * has only a sub-set of the feature available in the Tab or in the Browser Toolbox.
+ * In a WebExtensions add-on all the provided contexts (background and popup pages etc.),
+ * besides the Content Scripts which run in the content process, hooked to an existent
+ * tab, by creating a new WebExtensionActor which inherits from ChromeActor, we can
+ * provide a full features Addon Toolbox (which is basically like a BrowserToolbox which
+ * filters the visible sources and frames to the one that are related to the target
+ * add-on).
+ *
+ * @param conn DebuggerServerConnection
+ *        The connection to the client.
+ * @param addon AddonWrapper
+ *        The target addon.
+ */
+function WebExtensionActor(conn, addon) {
+  ChromeActor.call(this, conn);
+
+  this.id = addon.id;
+  this.addon = addon;
+
+  // Bind the _allowSource helper to this, it is used in the
+  // TabActor to lazily create the TabSources instance.
+  this._allowSource = this._allowSource.bind(this);
+
+  // Set the consoleAPIListener filtering options
+  // (retrieved and used in the related webconsole child actor).
+  this.consoleAPIListenerOptions = {
+    addonId: addon.id,
+  };
+
+  // This creates a Debugger instance for debugging all the add-on globals.
+  this.makeDebugger = makeDebugger.bind(null, {
+    findDebuggees: dbg => {
+      return dbg.findAllGlobals().filter(this._shouldAddNewGlobalAsDebuggee);
+    },
+    shouldAddNewGlobalAsDebuggee: this._shouldAddNewGlobalAsDebuggee.bind(this),
+  });
+
+  // Discover the preferred debug global for the target addon
+  this.preferredTargetWindow = null;
+  this._findAddonPreferredTargetWindow();
+
+  AddonManager.addAddonListener(this);
+}
+exports.WebExtensionActor = WebExtensionActor;
+
+WebExtensionActor.prototype = Object.create(ChromeActor.prototype);
+
+WebExtensionActor.prototype.actorPrefix = "webExtension";
+WebExtensionActor.prototype.constructor = WebExtensionActor;
+
+// NOTE: This is needed to catch in the webextension webconsole all the
+// errors raised by the WebExtension internals that are not currently
+// associated with any window.
+WebExtensionActor.prototype.isRootActor = true;
+
+WebExtensionActor.prototype.form = function () {
+  assert(this.actorID, "addon should have an actorID.");
+
+  let baseForm = ChromeActor.prototype.form.call(this);
+
+  return Object.assign(baseForm, {
+    actor: this.actorID,
+    id: this.id,
+    name: this.addon.name,
+    url: this.addon.sourceURI ? this.addon.sourceURI.spec : undefined,
+    iconURL: this.addon.iconURL,
+    debuggable: this.addon.isDebuggable,
+    temporarilyInstalled: this.addon.temporarilyInstalled,
+    isWebExtension: this.addon.isWebExtension,
+  });
+};
+
+WebExtensionActor.prototype._attach = function () {
+  // NOTE: we need to be sure that `this.window` can return a
+  // window before calling the ChromeActor.onAttach, or the TabActor
+  // will not be subscribed to the child doc shell updates.
+
+  // If a preferredTargetWindow exists, set it as the target for this actor
+  // when the client request to attach this actor.
+  if (this.preferredTargetWindow) {
+    this._setWindow(this.preferredTargetWindow);
+  } else {
+    this._createFallbackWindow();
+  }
+
+  // Call ChromeActor's _attach to listen for any new/destroyed chrome docshell
+  ChromeActor.prototype._attach.apply(this);
+};
+
+WebExtensionActor.prototype._detach = function () {
+  this._destroyFallbackWindow();
+
+  // Call ChromeActor's _detach to unsubscribe new/destroyed chrome docshell listeners.
+  ChromeActor.prototype._detach.apply(this);
+};
+
+/**
+ * Called when the actor is removed from the connection.
+ */
+WebExtensionActor.prototype.exit = function () {
+  AddonManager.removeAddonListener(this);
+
+  this.preferredTargetWindow = null;
+  this.addon = null;
+  this.id = null;
+
+  return ChromeActor.prototype.exit.apply(this);
+};
+
+// Addon Specific Remote Debugging requestTypes and methods.
+
+/**
+ * Reloads the addon.
+ */
+WebExtensionActor.prototype.onReload = function () {
+  return this.addon.reload()
+    .then(() => {
+      // send an empty response
+      return {};
+    });
+};
+
+/**
+ * Set the preferred global for the add-on (called from the AddonManager).
+ */
+WebExtensionActor.prototype.setOptions = function (addonOptions) {
+  if ("global" in addonOptions) {
+    // Set the proposed debug global as the preferred target window
+    // (the actor will eventually set it as the target once it is attached)
+    this.preferredTargetWindow = addonOptions.global;
+  }
+};
+
+// AddonManagerListener callbacks.
+
+WebExtensionActor.prototype.onInstalled = function (addon) {
+  if (addon.id != this.id) {
+    return;
+  }
+
+  // Update the AddonManager's addon object on reload/update.
+  this.addon = addon;
+};
+
+WebExtensionActor.prototype.onUninstalled = function (addon) {
+  if (addon != this.addon) {
+    return;
+  }
+
+  this.exit();
+};
+
+WebExtensionActor.prototype.onPropertyChanged = function (addon, changedPropNames) {
+  if (addon != this.addon) {
+    return;
+  }
+
+  // Refresh the preferred debug global on disabled/reloaded/upgraded addon.
+  if (changedPropNames.includes("debugGlobal")) {
+    this._findAddonPreferredTargetWindow();
+  }
+};
+
+// Private helpers
+
+WebExtensionActor.prototype._createFallbackWindow = function () {
+  if (this.fallbackWindow) {
+    // Skip if there is already an existent fallback window.
+    return;
+  }
+
+  // Create an empty hidden window as a fallback (e.g. the background page could be
+  // not defined for the target add-on or not yet when the actor instance has been
+  // created).
+  this.fallbackWebNav = Services.appShell.createWindowlessBrowser(true);
+  this.fallbackWebNav.loadURI(
+    `data:text/html;charset=utf-8,${FALLBACK_DOC_MESSAGE}`,
+    0, null, null, null
+  );
+
+  this.fallbackDocShell = this.fallbackWebNav
+    .QueryInterface(Ci.nsIInterfaceRequestor)
+    .getInterface(Ci.nsIDocShell);
+
+  Object.defineProperty(this, "docShell", {
+    value: this.fallbackDocShell,
+    configurable: true
+  });
+
+  // Save the reference to the fallback DOMWindow
+  this.fallbackWindow = this.fallbackDocShell.QueryInterface(Ci.nsIInterfaceRequestor)
+                                             .getInterface(Ci.nsIDOMWindow);
+};
+
+WebExtensionActor.prototype._destroyFallbackWindow = function () {
+  if (this.fallbackWebNav) {
+    // Explicitly close the fallback windowless browser to prevent it to leak
+    // (and to prevent it to freeze devtools xpcshell tests).
+    this.fallbackWebNav.loadURI("about:blank", 0, null, null, null);
+    this.fallbackWebNav.close();
+
+    this.fallbackWebNav = null;
+    this.fallbackWindow = null;
+  }
+};
+
+/**
+ * Discover the preferred debug global and switch to it if the addon has been attached.
+ */
+WebExtensionActor.prototype._findAddonPreferredTargetWindow = function () {
+  return new Promise(resolve => {
+    let activeAddon = XPIProvider.activeAddons.get(this.id);
+
+    if (!activeAddon) {
+      // The addon is not active, the background page is going to be destroyed,
+      // navigate to the fallback window (if it already exists).
+      resolve(null);
+    } else {
+      AddonManager.getAddonByInstanceID(activeAddon.instanceID)
+        .then(privateWrapper => {
+          let targetWindow = privateWrapper.getDebugGlobal();
+
+          // Do not use the preferred global if it is not a DOMWindow as expected.
+          if (!(targetWindow instanceof Ci.nsIDOMWindow)) {
+            targetWindow = null;
+          }
+
+          resolve(targetWindow);
+        });
+    }
+  }).then(preferredTargetWindow => {
+    this.preferredTargetWindow = preferredTargetWindow;
+
+    if (!preferredTargetWindow) {
+      // Create a fallback window if no preferred target window has been found.
+      this._createFallbackWindow();
+    } else if (this.attached) {
+      // Change the top level document if the actor is already attached.
+      this._changeTopLevelDocument(preferredTargetWindow);
+    }
+  });
+};
+
+/**
+ * Return an array of the json details related to an array/iterator of docShells.
+ */
+WebExtensionActor.prototype._docShellsToWindows = function (docshells) {
+  return ChromeActor.prototype._docShellsToWindows.call(this, docshells)
+                    .filter(windowDetails => {
+                      // filter the docShells based on the addon id
+                      return windowDetails.addonID == this.id;
+                    });
+};
+
+/**
+ * Return true if the given source is associated with this addon and should be
+ * added to the visible sources (retrieved and used by the webbrowser actor module).
+ */
+WebExtensionActor.prototype._allowSource = function (source) {
+  try {
+    let uri = Services.io.newURI(source.url, null, null);
+    let addonID = mapURIToAddonID(uri);
+
+    return addonID == this.id;
+  } catch (e) {
+    return false;
+  }
+};
+
+/**
+ * Return true if the given global is associated with this addon and should be
+ * added as a debuggee, false otherwise.
+ */
+WebExtensionActor.prototype._shouldAddNewGlobalAsDebuggee = function (newGlobal) {
+  const global = unwrapDebuggerObjectGlobal(newGlobal);
+
+  if (global instanceof Ci.nsIDOMWindow) {
+    return global.document.nodePrincipal.originAttributes.addonId == this.id;
+  }
+
+  try {
+    // This will fail for non-Sandbox objects, hence the try-catch block.
+    let metadata = Cu.getSandboxMetadata(global);
+    if (metadata) {
+      return metadata.addonID === this.id;
+    }
+  } catch (e) {
+    // Unable to retrieve the sandbox metadata.
+  }
+
+  return false;
+};
+
+/**
+ * Override WebExtensionActor requestTypes:
+ * - redefined `reload`, which should reload the target addon
+ *   (instead of the entire browser as the regular ChromeActor does).
+ */
+WebExtensionActor.prototype.requestTypes.reload = WebExtensionActor.prototype.onReload;
diff --git a/devtools/server/actors/webgl.js b/devtools/server/actors/webgl.js
new file mode 100644
index 000000000..137448647
--- /dev/null
+++ b/devtools/server/actors/webgl.js
@@ -0,0 +1,1322 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const {Cc, Ci, Cu, Cr} = require("chrome");
+const events = require("sdk/event/core");
+const promise = require("promise");
+const protocol = require("devtools/shared/protocol");
+const { ContentObserver } = require("devtools/shared/content-observer");
+const { on, once, off, emit } = events;
+const { method, Arg, Option, RetVal } = protocol;
+const {
+  shaderSpec,
+  programSpec,
+  webGLSpec,
+} = require("devtools/shared/specs/webgl");
+
+const WEBGL_CONTEXT_NAMES = ["webgl", "experimental-webgl", "moz-webgl"];
+
+// These traits are bit masks. Make sure they're powers of 2.
+const PROGRAM_DEFAULT_TRAITS = 0;
+const PROGRAM_BLACKBOX_TRAIT = 1;
+const PROGRAM_HIGHLIGHT_TRAIT = 2;
+
+/**
+ * A WebGL Shader contributing to building a WebGL Program.
+ * You can either retrieve, or compile the source of a shader, which will
+ * automatically inflict the necessary changes to the WebGL state.
+ */
+var ShaderActor = protocol.ActorClassWithSpec(shaderSpec, {
+  /**
+   * Create the shader actor.
+   *
+   * @param DebuggerServerConnection conn
+   *        The server connection.
+   * @param WebGLProgram program
+   *        The WebGL program being linked.
+   * @param WebGLShader shader
+   *        The cooresponding vertex or fragment shader.
+   * @param WebGLProxy proxy
+   *        The proxy methods for the WebGL context owning this shader.
+   */
+  initialize: function (conn, program, shader, proxy) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.program = program;
+    this.shader = shader;
+    this.text = proxy.getShaderSource(shader);
+    this.linkedProxy = proxy;
+  },
+
+  /**
+   * Gets the source code for this shader.
+   */
+  getText: function () {
+    return this.text;
+  },
+
+  /**
+   * Sets and compiles new source code for this shader.
+   */
+  compile: function (text) {
+    // Get the shader and corresponding program to change via the WebGL proxy.
+    let { linkedProxy: proxy, shader, program } = this;
+
+    // Get the new shader source to inject.
+    let oldText = this.text;
+    let newText = text;
+
+    // Overwrite the shader's source.
+    let error = proxy.compileShader(program, shader, this.text = newText);
+
+    // If something went wrong, revert to the previous shader.
+    if (error.compile || error.link) {
+      proxy.compileShader(program, shader, this.text = oldText);
+      return error;
+    }
+    return undefined;
+  }
+});
+
+/**
+ * A WebGL program is composed (at the moment, analogue to OpenGL ES 2.0)
+ * of two shaders: a vertex shader and a fragment shader.
+ */
+var ProgramActor = protocol.ActorClassWithSpec(programSpec, {
+  /**
+   * Create the program actor.
+   *
+   * @param DebuggerServerConnection conn
+   *        The server connection.
+   * @param WebGLProgram program
+   *        The WebGL program being linked.
+   * @param WebGLShader[] shaders
+   *        The WebGL program's cooresponding vertex and fragment shaders.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context owning this program.
+   * @param WebGLProxy proxy
+   *        The proxy methods for the WebGL context owning this program.
+   */
+  initialize: function (conn, [program, shaders, cache, proxy]) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this._shaderActorsCache = { vertex: null, fragment: null };
+    this.program = program;
+    this.shaders = shaders;
+    this.linkedCache = cache;
+    this.linkedProxy = proxy;
+  },
+
+  get ownerWindow() {
+    return this.linkedCache.ownerWindow;
+  },
+
+  get ownerContext() {
+    return this.linkedCache.ownerContext;
+  },
+
+  /**
+   * Gets the vertex shader linked to this program. This method guarantees
+   * a single actor instance per shader.
+   */
+  getVertexShader: function () {
+    return this._getShaderActor("vertex");
+  },
+
+  /**
+   * Gets the fragment shader linked to this program. This method guarantees
+   * a single actor instance per shader.
+   */
+  getFragmentShader: function () {
+    return this._getShaderActor("fragment");
+  },
+
+  /**
+   * Highlights any geometry rendered using this program.
+   */
+  highlight: function (tint) {
+    this.linkedProxy.highlightTint = tint;
+    this.linkedCache.setProgramTrait(this.program, PROGRAM_HIGHLIGHT_TRAIT);
+  },
+
+  /**
+   * Allows geometry to be rendered normally using this program.
+   */
+  unhighlight: function () {
+    this.linkedCache.unsetProgramTrait(this.program, PROGRAM_HIGHLIGHT_TRAIT);
+  },
+
+  /**
+   * Prevents any geometry from being rendered using this program.
+   */
+  blackbox: function () {
+    this.linkedCache.setProgramTrait(this.program, PROGRAM_BLACKBOX_TRAIT);
+  },
+
+  /**
+   * Allows geometry to be rendered using this program.
+   */
+  unblackbox: function () {
+    this.linkedCache.unsetProgramTrait(this.program, PROGRAM_BLACKBOX_TRAIT);
+  },
+
+  /**
+   * Returns a cached ShaderActor instance based on the required shader type.
+   *
+   * @param string type
+   *        Either "vertex" or "fragment".
+   * @return ShaderActor
+   *         The respective shader actor instance.
+   */
+  _getShaderActor: function (type) {
+    if (this._shaderActorsCache[type]) {
+      return this._shaderActorsCache[type];
+    }
+    let proxy = this.linkedProxy;
+    let shader = proxy.getShaderOfType(this.shaders, type);
+    let shaderActor = new ShaderActor(this.conn, this.program, shader, proxy);
+    return this._shaderActorsCache[type] = shaderActor;
+  }
+});
+
+/**
+ * The WebGL Actor handles simple interaction with a WebGL context via a few
+ * high-level methods. After instantiating this actor, you'll need to set it
+ * up by calling setup().
+ */
+var WebGLActor = exports.WebGLActor = protocol.ActorClassWithSpec(webGLSpec, {
+  initialize: function (conn, tabActor) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this.tabActor = tabActor;
+    this._onGlobalCreated = this._onGlobalCreated.bind(this);
+    this._onGlobalDestroyed = this._onGlobalDestroyed.bind(this);
+    this._onProgramLinked = this._onProgramLinked.bind(this);
+  },
+  destroy: function (conn) {
+    protocol.Actor.prototype.destroy.call(this, conn);
+    this.finalize();
+  },
+
+  /**
+   * Starts waiting for the current tab actor's document global to be
+   * created, in order to instrument the Canvas context and become
+   * aware of everything the content does WebGL-wise.
+   *
+   * See ContentObserver and WebGLInstrumenter for more details.
+   */
+  setup: function ({ reload }) {
+    if (this._initialized) {
+      return;
+    }
+    this._initialized = true;
+
+    this._programActorsCache = [];
+    this._webglObserver = new WebGLObserver();
+
+    on(this.tabActor, "window-ready", this._onGlobalCreated);
+    on(this.tabActor, "window-destroyed", this._onGlobalDestroyed);
+    on(this._webglObserver, "program-linked", this._onProgramLinked);
+
+    if (reload) {
+      this.tabActor.window.location.reload();
+    }
+  },
+
+  /**
+   * Stops listening for document global changes and puts this actor
+   * to hibernation. This method is called automatically just before the
+   * actor is destroyed.
+   */
+  finalize: function () {
+    if (!this._initialized) {
+      return;
+    }
+    this._initialized = false;
+
+    off(this.tabActor, "window-ready", this._onGlobalCreated);
+    off(this.tabActor, "window-destroyed", this._onGlobalDestroyed);
+    off(this._webglObserver, "program-linked", this._onProgramLinked);
+
+    this._programActorsCache = null;
+    this._contentObserver = null;
+    this._webglObserver = null;
+  },
+
+  /**
+   * Gets an array of cached program actors for the current tab actor's window.
+   * This is useful for dealing with bfcache, when no new programs are linked.
+   */
+  getPrograms: function () {
+    let id = ContentObserver.GetInnerWindowID(this.tabActor.window);
+    return this._programActorsCache.filter(e => e.ownerWindow == id);
+  },
+
+  /**
+   * Waits for one frame via `requestAnimationFrame` on the tab actor's window.
+   * Used in tests.
+   */
+  waitForFrame: function () {
+    let deferred = promise.defer();
+    this.tabActor.window.requestAnimationFrame(deferred.resolve);
+    return deferred.promise;
+  },
+
+  /**
+   * Gets a pixel's RGBA value from a context specified by selector
+   * and the coordinates of the pixel in question.
+   * Currently only used in tests.
+   *
+   * @param string selector
+   *        A string selector to select the canvas in question from the DOM.
+   * @param Object position
+   *        An object with an `x` and `y` property indicating coordinates of the pixel being inspected.
+   * @return Object
+   *        An object containing `r`, `g`, `b`, and `a` properties of the pixel.
+   */
+  getPixel: function ({ selector, position }) {
+    let { x, y } = position;
+    let canvas = this.tabActor.window.document.querySelector(selector);
+    let context = XPCNativeWrapper.unwrap(canvas.getContext("webgl"));
+    let { proxy } = this._webglObserver.for(context);
+    let height = canvas.height;
+
+    let buffer = new this.tabActor.window.Uint8Array(4);
+    buffer = XPCNativeWrapper.unwrap(buffer);
+
+    proxy.readPixels(x, height - y - 1, 1, 1, context.RGBA, context.UNSIGNED_BYTE, buffer);
+
+    return { r: buffer[0], g: buffer[1], b: buffer[2], a: buffer[3] };
+  },
+
+  /**
+   * Gets an array of all cached program actors belonging to all windows.
+   * This should only be used for tests.
+   */
+  _getAllPrograms: function () {
+    return this._programActorsCache;
+  },
+
+
+  /**
+   * Invoked whenever the current tab actor's document global is created.
+   */
+  _onGlobalCreated: function ({id, window, isTopLevel}) {
+    if (isTopLevel) {
+      WebGLInstrumenter.handle(window, this._webglObserver);
+      events.emit(this, "global-created", id);
+    }
+  },
+
+  /**
+   * Invoked whenever the current tab actor's inner window is destroyed.
+   */
+  _onGlobalDestroyed: function ({id, isTopLevel, isFrozen}) {
+    if (isTopLevel && !isFrozen) {
+      removeFromArray(this._programActorsCache, e => e.ownerWindow == id);
+      this._webglObserver.unregisterContextsForWindow(id);
+      events.emit(this, "global-destroyed", id);
+    }
+  },
+
+  /**
+   * Invoked whenever an observed WebGL context links a program.
+   */
+  _onProgramLinked: function (...args) {
+    let programActor = new ProgramActor(this.conn, args);
+    this._programActorsCache.push(programActor);
+    events.emit(this, "program-linked", programActor);
+  }
+});
+
+/**
+ * Instruments a HTMLCanvasElement with the appropriate inspection methods.
+ */
+var WebGLInstrumenter = {
+  /**
+   * Overrides the getContext method in the HTMLCanvasElement prototype.
+   *
+   * @param nsIDOMWindow window
+   *        The window to perform the instrumentation in.
+   * @param WebGLObserver observer
+   *        The observer watching function calls in the context.
+   */
+  handle: function (window, observer) {
+    let self = this;
+
+    let id = ContentObserver.GetInnerWindowID(window);
+    let canvasElem = XPCNativeWrapper.unwrap(window.HTMLCanvasElement);
+    let canvasPrototype = canvasElem.prototype;
+    let originalGetContext = canvasPrototype.getContext;
+
+    /**
+     * Returns a drawing context on the canvas, or null if the context ID is
+     * not supported. This override creates an observer for the targeted context
+     * type and instruments specific functions in the targeted context instance.
+     */
+    canvasPrototype.getContext = function (name, options) {
+      // Make sure a context was able to be created.
+      let context = originalGetContext.call(this, name, options);
+      if (!context) {
+        return context;
+      }
+      // Make sure a WebGL (not a 2D) context will be instrumented.
+      if (WEBGL_CONTEXT_NAMES.indexOf(name) == -1) {
+        return context;
+      }
+      // Repeated calls to 'getContext' return the same instance, no need to
+      // instrument everything again.
+      if (observer.for(context)) {
+        return context;
+      }
+
+      // Create a separate state storage for this context.
+      observer.registerContextForWindow(id, context);
+
+      // Link our observer to the new WebGL context methods.
+      for (let { timing, callback, functions } of self._methods) {
+        for (let func of functions) {
+          self._instrument(observer, context, func, callback, timing);
+        }
+      }
+
+      // Return the decorated context back to the content consumer, which
+      // will continue using it normally.
+      return context;
+    };
+  },
+
+  /**
+   * Overrides a specific method in a HTMLCanvasElement context.
+   *
+   * @param WebGLObserver observer
+   *        The observer watching function calls in the context.
+   * @param WebGLRenderingContext context
+   *        The targeted WebGL context instance.
+   * @param string funcName
+   *        The function to override.
+   * @param array callbackName [optional]
+   *        The two callback function names in the observer, corresponding to
+   *        the "before" and "after" invocation times. If unspecified, they will
+   *        default to the name of the function to override.
+   * @param number timing [optional]
+   *        When to issue the callback in relation to the actual context
+   *        function call. Availalble values are -1 for "before" (default)
+   *        1 for "after" and 0 for "before and after".
+   */
+  _instrument: function (observer, context, funcName, callbackName = [], timing = -1) {
+    let { cache, proxy } = observer.for(context);
+    let originalFunc = context[funcName];
+    let beforeFuncName = callbackName[0] || funcName;
+    let afterFuncName = callbackName[1] || callbackName[0] || funcName;
+
+    context[funcName] = function (...glArgs) {
+      if (timing <= 0 && !observer.suppressHandlers) {
+        let glBreak = observer[beforeFuncName](glArgs, cache, proxy);
+        if (glBreak) return undefined;
+      }
+
+      // Invoking .apply on an unxrayed content function doesn't work, because
+      // the arguments array is inaccessible to it. Get Xrays back.
+      let glResult = Cu.waiveXrays(Cu.unwaiveXrays(originalFunc).apply(this, glArgs));
+
+      if (timing >= 0 && !observer.suppressHandlers) {
+        let glBreak = observer[afterFuncName](glArgs, glResult, cache, proxy);
+        if (glBreak) return undefined;
+      }
+
+      return glResult;
+    };
+  },
+
+  /**
+   * Override mappings for WebGL methods.
+   */
+  _methods: [{
+    timing: 1, // after
+    functions: [
+      "linkProgram", "getAttribLocation", "getUniformLocation"
+    ]
+  }, {
+    timing: -1, // before
+    callback: [
+      "toggleVertexAttribArray"
+    ],
+    functions: [
+      "enableVertexAttribArray", "disableVertexAttribArray"
+    ]
+  }, {
+    timing: -1, // before
+    callback: [
+      "attribute_"
+    ],
+    functions: [
+      "vertexAttrib1f", "vertexAttrib2f", "vertexAttrib3f", "vertexAttrib4f",
+      "vertexAttrib1fv", "vertexAttrib2fv", "vertexAttrib3fv", "vertexAttrib4fv",
+      "vertexAttribPointer"
+    ]
+  }, {
+    timing: -1, // before
+    callback: [
+      "uniform_"
+    ],
+    functions: [
+      "uniform1i", "uniform2i", "uniform3i", "uniform4i",
+      "uniform1f", "uniform2f", "uniform3f", "uniform4f",
+      "uniform1iv", "uniform2iv", "uniform3iv", "uniform4iv",
+      "uniform1fv", "uniform2fv", "uniform3fv", "uniform4fv",
+      "uniformMatrix2fv", "uniformMatrix3fv", "uniformMatrix4fv"
+    ]
+  }, {
+    timing: -1, // before
+    functions: [
+      "useProgram", "enable", "disable", "blendColor",
+      "blendEquation", "blendEquationSeparate",
+      "blendFunc", "blendFuncSeparate"
+    ]
+  }, {
+    timing: 0, // before and after
+    callback: [
+      "beforeDraw_", "afterDraw_"
+    ],
+    functions: [
+      "drawArrays", "drawElements"
+    ]
+  }]
+  // TODO: It'd be a good idea to handle other functions as well:
+  //   - getActiveUniform
+  //   - getUniform
+  //   - getActiveAttrib
+  //   - getVertexAttrib
+};
+
+/**
+ * An observer that captures a WebGL context's method calls.
+ */
+function WebGLObserver() {
+  this._contexts = new Map();
+}
+
+WebGLObserver.prototype = {
+  _contexts: null,
+
+  /**
+   * Creates a WebGLCache and a WebGLProxy for the specified window and context.
+   *
+   * @param number id
+   *        The id of the window containing the WebGL context.
+   * @param WebGLRenderingContext context
+   *        The WebGL context used in the cache and proxy instances.
+   */
+  registerContextForWindow: function (id, context) {
+    let cache = new WebGLCache(id, context);
+    let proxy = new WebGLProxy(id, context, cache, this);
+    cache.refreshState(proxy);
+
+    this._contexts.set(context, {
+      ownerWindow: id,
+      cache: cache,
+      proxy: proxy
+    });
+  },
+
+  /**
+   * Removes all WebGLCache and WebGLProxy instances for a particular window.
+   *
+   * @param number id
+   *        The id of the window containing the WebGL context.
+   */
+  unregisterContextsForWindow: function (id) {
+    removeFromMap(this._contexts, e => e.ownerWindow == id);
+  },
+
+  /**
+   * Gets the WebGLCache and WebGLProxy instances for a particular context.
+   *
+   * @param WebGLRenderingContext context
+   *        The WebGL context used in the cache and proxy instances.
+   * @return object
+   *         An object containing the corresponding { cache, proxy } instances.
+   */
+  for: function (context) {
+    return this._contexts.get(context);
+  },
+
+  /**
+   * Set this flag to true to stop observing any context function calls.
+   */
+  suppressHandlers: false,
+
+  /**
+   * Called immediately *after* 'linkProgram' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param void glResult
+   *        The returned value of the original function call.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   * @param WebGLProxy proxy
+   *        The proxy methods for the WebGL context initiating this call.
+   */
+  linkProgram: function (glArgs, glResult, cache, proxy) {
+    let program = glArgs[0];
+    let shaders = proxy.getAttachedShaders(program);
+    cache.addProgram(program, PROGRAM_DEFAULT_TRAITS);
+    emit(this, "program-linked", program, shaders, cache, proxy);
+  },
+
+  /**
+   * Called immediately *after* 'getAttribLocation' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param GLint glResult
+   *        The returned value of the original function call.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  getAttribLocation: function (glArgs, glResult, cache) {
+    // Make sure the attribute's value is legal before caching.
+    if (glResult < 0) {
+      return;
+    }
+    let [program, name] = glArgs;
+    cache.addAttribute(program, name, glResult);
+  },
+
+  /**
+   * Called immediately *after* 'getUniformLocation' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLUniformLocation glResult
+   *        The returned value of the original function call.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  getUniformLocation: function (glArgs, glResult, cache) {
+    // Make sure the uniform's value is legal before caching.
+    if (!glResult) {
+      return;
+    }
+    let [program, name] = glArgs;
+    cache.addUniform(program, name, glResult);
+  },
+
+  /**
+   * Called immediately *before* 'enableVertexAttribArray' or
+   * 'disableVertexAttribArray'is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  toggleVertexAttribArray: function (glArgs, cache) {
+    glArgs[0] = cache.getCurrentAttributeLocation(glArgs[0]);
+    return glArgs[0] < 0; // Return true to break original function call.
+  },
+
+  /**
+   * Called immediately *before* 'attribute_' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  attribute_: function (glArgs, cache) {
+    glArgs[0] = cache.getCurrentAttributeLocation(glArgs[0]);
+    return glArgs[0] < 0; // Return true to break original function call.
+  },
+
+  /**
+   * Called immediately *before* 'uniform_' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  uniform_: function (glArgs, cache) {
+    glArgs[0] = cache.getCurrentUniformLocation(glArgs[0]);
+    return !glArgs[0]; // Return true to break original function call.
+  },
+
+  /**
+   * Called immediately *before* 'useProgram' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  useProgram: function (glArgs, cache) {
+    // Manually keeping a cache and not using gl.getParameter(CURRENT_PROGRAM)
+    // because gl.get* functions are slow as potatoes.
+    cache.currentProgram = glArgs[0];
+  },
+
+  /**
+   * Called immediately *before* 'enable' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  enable: function (glArgs, cache) {
+    cache.currentState[glArgs[0]] = true;
+  },
+
+  /**
+   * Called immediately *before* 'disable' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  disable: function (glArgs, cache) {
+    cache.currentState[glArgs[0]] = false;
+  },
+
+  /**
+   * Called immediately *before* 'blendColor' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  blendColor: function (glArgs, cache) {
+    let blendColor = cache.currentState.blendColor;
+    blendColor[0] = glArgs[0];
+    blendColor[1] = glArgs[1];
+    blendColor[2] = glArgs[2];
+    blendColor[3] = glArgs[3];
+  },
+
+  /**
+   * Called immediately *before* 'blendEquation' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  blendEquation: function (glArgs, cache) {
+    let state = cache.currentState;
+    state.blendEquationRgb = state.blendEquationAlpha = glArgs[0];
+  },
+
+  /**
+   * Called immediately *before* 'blendEquationSeparate' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  blendEquationSeparate: function (glArgs, cache) {
+    let state = cache.currentState;
+    state.blendEquationRgb = glArgs[0];
+    state.blendEquationAlpha = glArgs[1];
+  },
+
+  /**
+   * Called immediately *before* 'blendFunc' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  blendFunc: function (glArgs, cache) {
+    let state = cache.currentState;
+    state.blendSrcRgb = state.blendSrcAlpha = glArgs[0];
+    state.blendDstRgb = state.blendDstAlpha = glArgs[1];
+  },
+
+  /**
+   * Called immediately *before* 'blendFuncSeparate' is requested in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   */
+  blendFuncSeparate: function (glArgs, cache) {
+    let state = cache.currentState;
+    state.blendSrcRgb = glArgs[0];
+    state.blendDstRgb = glArgs[1];
+    state.blendSrcAlpha = glArgs[2];
+    state.blendDstAlpha = glArgs[3];
+  },
+
+  /**
+   * Called immediately *before* 'drawArrays' or 'drawElements' is requested
+   * in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   * @param WebGLProxy proxy
+   *        The proxy methods for the WebGL context initiating this call.
+   */
+  beforeDraw_: function (glArgs, cache, proxy) {
+    let traits = cache.currentProgramTraits;
+
+    // Handle program blackboxing.
+    if (traits & PROGRAM_BLACKBOX_TRAIT) {
+      return true; // Return true to break original function call.
+    }
+    // Handle program highlighting.
+    if (traits & PROGRAM_HIGHLIGHT_TRAIT) {
+      proxy.enableHighlighting();
+    }
+
+    return false;
+  },
+
+  /**
+   * Called immediately *after* 'drawArrays' or 'drawElements' is requested
+   * in the context.
+   *
+   * @param array glArgs
+   *        Overridable arguments with which the function is called.
+   * @param void glResult
+   *        The returned value of the original function call.
+   * @param WebGLCache cache
+   *        The state storage for the WebGL context initiating this call.
+   * @param WebGLProxy proxy
+   *        The proxy methods for the WebGL context initiating this call.
+   */
+  afterDraw_: function (glArgs, glResult, cache, proxy) {
+    let traits = cache.currentProgramTraits;
+
+    // Handle program highlighting.
+    if (traits & PROGRAM_HIGHLIGHT_TRAIT) {
+      proxy.disableHighlighting();
+    }
+  }
+};
+
+/**
+ * A mechanism for storing a single WebGL context's state, programs, shaders,
+ * attributes or uniforms.
+ *
+ * @param number id
+ *        The id of the window containing the WebGL context.
+ * @param WebGLRenderingContext context
+ *        The WebGL context for which the state is stored.
+ */
+function WebGLCache(id, context) {
+  this._id = id;
+  this._gl = context;
+  this._programs = new Map();
+  this.currentState = {};
+}
+
+WebGLCache.prototype = {
+  _id: 0,
+  _gl: null,
+  _programs: null,
+  _currentProgramInfo: null,
+  _currentAttributesMap: null,
+  _currentUniformsMap: null,
+
+  get ownerWindow() {
+    return this._id;
+  },
+
+  get ownerContext() {
+    return this._gl;
+  },
+
+  /**
+   * A collection of flags or properties representing the context's state.
+   * Implemented as an object hash and not a Map instance because keys are
+   * always either strings or numbers.
+   */
+  currentState: null,
+
+  /**
+   * Populates the current state with values retrieved from the context.
+   *
+   * @param WebGLProxy proxy
+   *        The proxy methods for the WebGL context owning the state.
+   */
+  refreshState: function (proxy) {
+    let gl = this._gl;
+    let s = this.currentState;
+
+    // Populate only with the necessary parameters. Not all default WebGL
+    // state values are required.
+    s[gl.BLEND] = proxy.isEnabled("BLEND");
+    s.blendColor = proxy.getParameter("BLEND_COLOR");
+    s.blendEquationRgb = proxy.getParameter("BLEND_EQUATION_RGB");
+    s.blendEquationAlpha = proxy.getParameter("BLEND_EQUATION_ALPHA");
+    s.blendSrcRgb = proxy.getParameter("BLEND_SRC_RGB");
+    s.blendSrcAlpha = proxy.getParameter("BLEND_SRC_ALPHA");
+    s.blendDstRgb = proxy.getParameter("BLEND_DST_RGB");
+    s.blendDstAlpha = proxy.getParameter("BLEND_DST_ALPHA");
+  },
+
+  /**
+   * Adds a program to the cache.
+   *
+   * @param WebGLProgram program
+   *        The shader for which the traits are to be cached.
+   * @param number traits
+   *        A default properties mask set for the program.
+   */
+  addProgram: function (program, traits) {
+    this._programs.set(program, {
+      traits: traits,
+      attributes: [], // keys are GLints (numbers)
+      uniforms: new Map() // keys are WebGLUniformLocations (objects)
+    });
+  },
+
+  /**
+   * Adds a specific trait to a program. The effect of such properties is
+   * determined by the consumer of this cache.
+   *
+   * @param WebGLProgram program
+   *        The program to add the trait to.
+   * @param number trait
+   *        The property added to the program.
+   */
+  setProgramTrait: function (program, trait) {
+    this._programs.get(program).traits |= trait;
+  },
+
+  /**
+   * Removes a specific trait from a program.
+   *
+   * @param WebGLProgram program
+   *        The program to remove the trait from.
+   * @param number trait
+   *        The property removed from the program.
+   */
+  unsetProgramTrait: function (program, trait) {
+    this._programs.get(program).traits &= ~trait;
+  },
+
+  /**
+   * Sets the currently used program in the context.
+   * @param WebGLProgram program
+   */
+  set currentProgram(program) {
+    let programInfo = this._programs.get(program);
+    if (programInfo == null) {
+      return;
+    }
+    this._currentProgramInfo = programInfo;
+    this._currentAttributesMap = programInfo.attributes;
+    this._currentUniformsMap = programInfo.uniforms;
+  },
+
+  /**
+   * Gets the traits for the currently used program.
+   * @return number
+   */
+  get currentProgramTraits() {
+    return this._currentProgramInfo.traits;
+  },
+
+  /**
+   * Adds an attribute to the cache.
+   *
+   * @param WebGLProgram program
+   *        The program for which the attribute is bound.
+   * @param string name
+   *        The attribute name.
+   * @param GLint value
+   *        The attribute value.
+   */
+  addAttribute: function (program, name, value) {
+    this._programs.get(program).attributes[value] = {
+      name: name,
+      value: value
+    };
+  },
+
+  /**
+   * Adds a uniform to the cache.
+   *
+   * @param WebGLProgram program
+   *        The program for which the uniform is bound.
+   * @param string name
+   *        The uniform name.
+   * @param WebGLUniformLocation value
+   *        The uniform value.
+   */
+  addUniform: function (program, name, value) {
+    this._programs.get(program).uniforms.set(new XPCNativeWrapper(value), {
+      name: name,
+      value: value
+    });
+  },
+
+  /**
+   * Updates the attribute locations for a specific program.
+   * This is necessary, for example, when the shader is relinked and all the
+   * attribute locations become obsolete.
+   *
+   * @param WebGLProgram program
+   *        The program for which the attributes need updating.
+   */
+  updateAttributesForProgram: function (program) {
+    let attributes = this._programs.get(program).attributes;
+    for (let attribute of attributes) {
+      attribute.value = this._gl.getAttribLocation(program, attribute.name);
+    }
+  },
+
+  /**
+   * Updates the uniform locations for a specific program.
+   * This is necessary, for example, when the shader is relinked and all the
+   * uniform locations become obsolete.
+   *
+   * @param WebGLProgram program
+   *        The program for which the uniforms need updating.
+   */
+  updateUniformsForProgram: function (program) {
+    let uniforms = this._programs.get(program).uniforms;
+    for (let [, uniform] of uniforms) {
+      uniform.value = this._gl.getUniformLocation(program, uniform.name);
+    }
+  },
+
+  /**
+   * Gets the actual attribute location in a specific program.
+   * When relinked, all the attribute locations become obsolete and are updated
+   * in the cache. This method returns the (current) real attribute location.
+   *
+   * @param GLint initialValue
+   *        The initial attribute value.
+   * @return GLint
+   *         The current attribute value, or the initial value if it's already
+   *         up to date with its corresponding program.
+   */
+  getCurrentAttributeLocation: function (initialValue) {
+    let attributes = this._currentAttributesMap;
+    let currentInfo = attributes ? attributes[initialValue] : null;
+    return currentInfo ? currentInfo.value : initialValue;
+  },
+
+  /**
+   * Gets the actual uniform location in a specific program.
+   * When relinked, all the uniform locations become obsolete and are updated
+   * in the cache. This method returns the (current) real uniform location.
+   *
+   * @param WebGLUniformLocation initialValue
+   *        The initial uniform value.
+   * @return WebGLUniformLocation
+   *         The current uniform value, or the initial value if it's already
+   *         up to date with its corresponding program.
+   */
+  getCurrentUniformLocation: function (initialValue) {
+    let uniforms = this._currentUniformsMap;
+    let currentInfo = uniforms ? uniforms.get(initialValue) : null;
+    return currentInfo ? currentInfo.value : initialValue;
+  }
+};
+
+/**
+ * A mechanism for injecting or qureying state into/from a single WebGL context.
+ *
+ * Any interaction with a WebGL context should go through this proxy.
+ * Otherwise, the corresponding observer would register the calls as coming
+ * from content, which is usually not desirable. Infinite call stacks are bad.
+ *
+ * @param number id
+ *        The id of the window containing the WebGL context.
+ * @param WebGLRenderingContext context
+ *        The WebGL context used for the proxy methods.
+ * @param WebGLCache cache
+ *        The state storage for the corresponding context.
+ * @param WebGLObserver observer
+ *        The observer watching function calls in the corresponding context.
+ */
+function WebGLProxy(id, context, cache, observer) {
+  this._id = id;
+  this._gl = context;
+  this._cache = cache;
+  this._observer = observer;
+
+  let exports = [
+    "isEnabled",
+    "getParameter",
+    "getAttachedShaders",
+    "getShaderSource",
+    "getShaderOfType",
+    "compileShader",
+    "enableHighlighting",
+    "disableHighlighting",
+    "readPixels"
+  ];
+  exports.forEach(e => this[e] = (...args) => this._call(e, args));
+}
+
+WebGLProxy.prototype = {
+  _id: 0,
+  _gl: null,
+  _cache: null,
+  _observer: null,
+
+  get ownerWindow() {
+    return this._id;
+  },
+  get ownerContext() {
+    return this._gl;
+  },
+
+  /**
+   * Test whether a WebGL capability is enabled.
+   *
+   * @param string name
+   *        The WebGL capability name, for example "BLEND".
+   * @return boolean
+   *         True if enabled, false otherwise.
+   */
+  _isEnabled: function (name) {
+    return this._gl.isEnabled(this._gl[name]);
+  },
+
+  /**
+   * Returns the value for the specified WebGL parameter name.
+   *
+   * @param string name
+   *        The WebGL parameter name, for example "BLEND_COLOR".
+   * @return any
+   *         The corresponding parameter's value.
+   */
+  _getParameter: function (name) {
+    return this._gl.getParameter(this._gl[name]);
+  },
+
+  /**
+   * Returns the renderbuffer property value for the specified WebGL parameter.
+   * If no renderbuffer binding is available, null is returned.
+   *
+   * @param string name
+   *        The WebGL parameter name, for example "BLEND_COLOR".
+   * @return any
+   *         The corresponding parameter's value.
+   */
+  _getRenderbufferParameter: function (name) {
+    if (!this._getParameter("RENDERBUFFER_BINDING")) {
+      return null;
+    }
+    let gl = this._gl;
+    return gl.getRenderbufferParameter(gl.RENDERBUFFER, gl[name]);
+  },
+
+  /**
+   * Returns the framebuffer property value for the specified WebGL parameter.
+   * If no framebuffer binding is available, null is returned.
+   *
+   * @param string type
+   *        The framebuffer object attachment point, for example "COLOR_ATTACHMENT0".
+   * @param string name
+   *        The WebGL parameter name, for example "FRAMEBUFFER_ATTACHMENT_OBJECT_NAME".
+   *        If unspecified, defaults to "FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE".
+   * @return any
+   *         The corresponding parameter's value.
+   */
+  _getFramebufferAttachmentParameter: function (type, name = "FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE") {
+    if (!this._getParameter("FRAMEBUFFER_BINDING")) {
+      return null;
+    }
+    let gl = this._gl;
+    return gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl[type], gl[name]);
+  },
+
+  /**
+   * Returns the shader objects attached to a program object.
+   *
+   * @param WebGLProgram program
+   *        The program for which to retrieve the attached shaders.
+   * @return array
+   *         The attached vertex and fragment shaders.
+   */
+  _getAttachedShaders: function (program) {
+    return this._gl.getAttachedShaders(program);
+  },
+
+  /**
+   * Returns the source code string from a shader object.
+   *
+   * @param WebGLShader shader
+   *        The shader for which to retrieve the source code.
+   * @return string
+   *         The shader's source code.
+   */
+  _getShaderSource: function (shader) {
+    return this._gl.getShaderSource(shader);
+  },
+
+  /**
+   * Finds a shader of the specified type in a list.
+   *
+   * @param WebGLShader[] shaders
+   *        The shaders for which to check the type.
+   * @param string type
+   *        Either "vertex" or "fragment".
+   * @return WebGLShader | null
+   *         The shader of the specified type, or null if nothing is found.
+   */
+  _getShaderOfType: function (shaders, type) {
+    let gl = this._gl;
+    let shaderTypeEnum = {
+      vertex: gl.VERTEX_SHADER,
+      fragment: gl.FRAGMENT_SHADER
+    }[type];
+
+    for (let shader of shaders) {
+      if (gl.getShaderParameter(shader, gl.SHADER_TYPE) == shaderTypeEnum) {
+        return shader;
+      }
+    }
+    return null;
+  },
+
+  /**
+   * Changes a shader's source code and relinks the respective program.
+   *
+   * @param WebGLProgram program
+   *        The program who's linked shader is to be modified.
+   * @param WebGLShader shader
+   *        The shader to be modified.
+   * @param string text
+   *        The new shader source code.
+   * @return object
+   *         An object containing the compilation and linking status.
+   */
+  _compileShader: function (program, shader, text) {
+    let gl = this._gl;
+    gl.shaderSource(shader, text);
+    gl.compileShader(shader);
+    gl.linkProgram(program);
+
+    let error = { compile: "", link: "" };
+
+    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
+      error.compile = gl.getShaderInfoLog(shader);
+    }
+    if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
+      error.link = gl.getShaderInfoLog(shader);
+    }
+
+    this._cache.updateAttributesForProgram(program);
+    this._cache.updateUniformsForProgram(program);
+
+    return error;
+  },
+
+  /**
+   * Enables color blending based on the geometry highlight tint.
+   */
+  _enableHighlighting: function () {
+    let gl = this._gl;
+
+    // Avoid changing the blending params when "rendering to texture".
+
+    // Check drawing to a custom framebuffer bound to the default renderbuffer.
+    let hasFramebuffer = this._getParameter("FRAMEBUFFER_BINDING");
+    let hasRenderbuffer = this._getParameter("RENDERBUFFER_BINDING");
+    if (hasFramebuffer && !hasRenderbuffer) {
+      return;
+    }
+
+    // Check drawing to a depth or stencil component of the framebuffer.
+    let writesDepth = this._getFramebufferAttachmentParameter("DEPTH_ATTACHMENT");
+    let writesStencil = this._getFramebufferAttachmentParameter("STENCIL_ATTACHMENT");
+    if (writesDepth || writesStencil) {
+      return;
+    }
+
+    // Non-premultiplied alpha blending based on a predefined constant color.
+    // Simply using gl.colorMask won't work, because we want non-tinted colors
+    // to be drawn as black, not ignored.
+    gl.enable(gl.BLEND);
+    gl.blendColor.apply(gl, this.highlightTint);
+    gl.blendEquation(gl.FUNC_ADD);
+    gl.blendFunc(gl.CONSTANT_COLOR, gl.ONE_MINUS_SRC_ALPHA, gl.CONSTANT_COLOR, gl.ZERO);
+    this.wasHighlighting = true;
+  },
+
+  /**
+   * Disables color blending based on the geometry highlight tint, by
+   * reverting the corresponding params back to their original values.
+   */
+  _disableHighlighting: function () {
+    let gl = this._gl;
+    let s = this._cache.currentState;
+
+    gl[s[gl.BLEND] ? "enable" : "disable"](gl.BLEND);
+    gl.blendColor.apply(gl, s.blendColor);
+    gl.blendEquationSeparate(s.blendEquationRgb, s.blendEquationAlpha);
+    gl.blendFuncSeparate(s.blendSrcRgb, s.blendDstRgb, s.blendSrcAlpha, s.blendDstAlpha);
+  },
+
+  /**
+   * Returns the pixel values at the position specified on the canvas.
+   */
+  _readPixels: function (x, y, w, h, format, type, buffer) {
+    this._gl.readPixels(x, y, w, h, format, type, buffer);
+  },
+
+  /**
+   * The color tint used for highlighting geometry.
+   * @see _enableHighlighting and _disableHighlighting.
+   */
+  highlightTint: [0, 0, 0, 0],
+
+  /**
+   * Executes a function in this object.
+   *
+   * This method makes sure that any handlers in the context observer are
+   * suppressed, hence stopping observing any context function calls.
+   *
+   * @param string funcName
+   *        The function to call.
+   * @param array args
+   *        An array of arguments.
+   * @return any
+   *         The called function result.
+   */
+  _call: function (funcName, args) {
+    let prevState = this._observer.suppressHandlers;
+
+    this._observer.suppressHandlers = true;
+    let result = this["_" + funcName].apply(this, args);
+    this._observer.suppressHandlers = prevState;
+
+    return result;
+  }
+};
+
+// Utility functions.
+
+function removeFromMap(map, predicate) {
+  for (let [key, value] of map) {
+    if (predicate(value)) {
+      map.delete(key);
+    }
+  }
+}
+
+function removeFromArray(array, predicate) {
+  for (let i = 0; i < array.length;) {
+    if (predicate(array[i])) {
+      array.splice(i, 1);
+    } else {
+      i++;
+    }
+  }
+}
diff --git a/devtools/server/actors/worker.js b/devtools/server/actors/worker.js
new file mode 100644
index 000000000..1937229d5
--- /dev/null
+++ b/devtools/server/actors/worker.js
@@ -0,0 +1,611 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { Ci } = require("chrome");
+const { DebuggerServer } = require("devtools/server/main");
+const Services = require("Services");
+const { XPCOMUtils } = require("resource://gre/modules/XPCOMUtils.jsm");
+const protocol = require("devtools/shared/protocol");
+const { Arg, method, RetVal } = protocol;
+const {
+  workerSpec,
+  pushSubscriptionSpec,
+  serviceWorkerRegistrationSpec,
+  serviceWorkerSpec,
+} = require("devtools/shared/specs/worker");
+
+loader.lazyRequireGetter(this, "ChromeUtils");
+loader.lazyRequireGetter(this, "events", "sdk/event/core");
+
+XPCOMUtils.defineLazyServiceGetter(
+  this, "wdm",
+  "@mozilla.org/dom/workers/workerdebuggermanager;1",
+  "nsIWorkerDebuggerManager"
+);
+
+XPCOMUtils.defineLazyServiceGetter(
+  this, "swm",
+  "@mozilla.org/serviceworkers/manager;1",
+  "nsIServiceWorkerManager"
+);
+
+XPCOMUtils.defineLazyServiceGetter(
+  this, "PushService",
+  "@mozilla.org/push/Service;1",
+  "nsIPushService"
+);
+
+function matchWorkerDebugger(dbg, options) {
+  if ("type" in options && dbg.type !== options.type) {
+    return false;
+  }
+  if ("window" in options) {
+    let window = dbg.window;
+    while (window !== null && window.parent !== window) {
+      window = window.parent;
+    }
+
+    if (window !== options.window) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+let WorkerActor = protocol.ActorClassWithSpec(workerSpec, {
+  initialize(conn, dbg) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this._dbg = dbg;
+    this._attached = false;
+    this._threadActor = null;
+    this._transport = null;
+  },
+
+  form(detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+    let form = {
+      actor: this.actorID,
+      consoleActor: this._consoleActor,
+      url: this._dbg.url,
+      type: this._dbg.type
+    };
+    if (this._dbg.type === Ci.nsIWorkerDebugger.TYPE_SERVICE) {
+      let registration = this._getServiceWorkerRegistrationInfo();
+      form.scope = registration.scope;
+    }
+    return form;
+  },
+
+  attach() {
+    if (this._dbg.isClosed) {
+      return { error: "closed" };
+    }
+
+    if (!this._attached) {
+      // Automatically disable their internal timeout that shut them down
+      // Should be refactored by having actors specific to service workers
+      if (this._dbg.type == Ci.nsIWorkerDebugger.TYPE_SERVICE) {
+        let worker = this._getServiceWorkerInfo();
+        if (worker) {
+          worker.attachDebugger();
+        }
+      }
+      this._dbg.addListener(this);
+      this._attached = true;
+    }
+
+    return {
+      type: "attached",
+      url: this._dbg.url
+    };
+  },
+
+  detach() {
+    if (!this._attached) {
+      return { error: "wrongState" };
+    }
+
+    this._detach();
+
+    return { type: "detached" };
+  },
+
+  destroy() {
+    protocol.Actor.prototype.destroy.call(this);
+    if (this._attached) {
+      this._detach();
+    }
+  },
+
+  disconnect() {
+    this.destroy();
+  },
+
+  connect(options) {
+    if (!this._attached) {
+      return { error: "wrongState" };
+    }
+
+    if (this._threadActor !== null) {
+      return {
+        type: "connected",
+        threadActor: this._threadActor
+      };
+    }
+
+    return DebuggerServer.connectToWorker(
+      this.conn, this._dbg, this.actorID, options
+    ).then(({ threadActor, transport, consoleActor }) => {
+      this._threadActor = threadActor;
+      this._transport = transport;
+      this._consoleActor = consoleActor;
+
+      return {
+        type: "connected",
+        threadActor: this._threadActor,
+        consoleActor: this._consoleActor
+      };
+    }, (error) => {
+      return { error: error.toString() };
+    });
+  },
+
+  push() {
+    if (this._dbg.type !== Ci.nsIWorkerDebugger.TYPE_SERVICE) {
+      return { error: "wrongType" };
+    }
+    let registration = this._getServiceWorkerRegistrationInfo();
+    let originAttributes = ChromeUtils.originAttributesToSuffix(
+      this._dbg.principal.originAttributes);
+    swm.sendPushEvent(originAttributes, registration.scope);
+    return { type: "pushed" };
+  },
+
+  onClose() {
+    if (this._attached) {
+      this._detach();
+    }
+
+    this.conn.sendActorEvent(this.actorID, "close");
+  },
+
+  onError(filename, lineno, message) {
+    reportError("ERROR:" + filename + ":" + lineno + ":" + message + "\n");
+  },
+
+  _getServiceWorkerRegistrationInfo() {
+    return swm.getRegistrationByPrincipal(this._dbg.principal, this._dbg.url);
+  },
+
+  _getServiceWorkerInfo() {
+    let registration = this._getServiceWorkerRegistrationInfo();
+    return registration.getWorkerByID(this._dbg.serviceWorkerID);
+  },
+
+  _detach() {
+    if (this._threadActor !== null) {
+      this._transport.close();
+      this._transport = null;
+      this._threadActor = null;
+    }
+
+    // If the worker is already destroyed, nsIWorkerDebugger.type throws
+    // (_dbg.closed appears to be false when it throws)
+    let type;
+    try {
+      type = this._dbg.type;
+    } catch (e) {}
+
+    if (type == Ci.nsIWorkerDebugger.TYPE_SERVICE) {
+      let worker = this._getServiceWorkerInfo();
+      if (worker) {
+        worker.detachDebugger();
+      }
+    }
+
+    this._dbg.removeListener(this);
+    this._attached = false;
+  }
+});
+
+exports.WorkerActor = WorkerActor;
+
+function WorkerActorList(conn, options) {
+  this._conn = conn;
+  this._options = options;
+  this._actors = new Map();
+  this._onListChanged = null;
+  this._mustNotify = false;
+  this.onRegister = this.onRegister.bind(this);
+  this.onUnregister = this.onUnregister.bind(this);
+}
+
+WorkerActorList.prototype = {
+  getList() {
+    // Create a set of debuggers.
+    let dbgs = new Set();
+    let e = wdm.getWorkerDebuggerEnumerator();
+    while (e.hasMoreElements()) {
+      let dbg = e.getNext().QueryInterface(Ci.nsIWorkerDebugger);
+      if (matchWorkerDebugger(dbg, this._options)) {
+        dbgs.add(dbg);
+      }
+    }
+
+    // Delete each actor for which we don't have a debugger.
+    for (let [dbg, ] of this._actors) {
+      if (!dbgs.has(dbg)) {
+        this._actors.delete(dbg);
+      }
+    }
+
+    // Create an actor for each debugger for which we don't have one.
+    for (let dbg of dbgs) {
+      if (!this._actors.has(dbg)) {
+        this._actors.set(dbg, new WorkerActor(this._conn, dbg));
+      }
+    }
+
+    let actors = [];
+    for (let [, actor] of this._actors) {
+      actors.push(actor);
+    }
+
+    if (!this._mustNotify) {
+      if (this._onListChanged !== null) {
+        wdm.addListener(this);
+      }
+      this._mustNotify = true;
+    }
+
+    return Promise.resolve(actors);
+  },
+
+  get onListChanged() {
+    return this._onListChanged;
+  },
+
+  set onListChanged(onListChanged) {
+    if (typeof onListChanged !== "function" && onListChanged !== null) {
+      throw new Error("onListChanged must be either a function or null.");
+    }
+    if (onListChanged === this._onListChanged) {
+      return;
+    }
+
+    if (this._mustNotify) {
+      if (this._onListChanged === null && onListChanged !== null) {
+        wdm.addListener(this);
+      }
+      if (this._onListChanged !== null && onListChanged === null) {
+        wdm.removeListener(this);
+      }
+    }
+    this._onListChanged = onListChanged;
+  },
+
+  _notifyListChanged() {
+    this._onListChanged();
+
+    if (this._onListChanged !== null) {
+      wdm.removeListener(this);
+    }
+    this._mustNotify = false;
+  },
+
+  onRegister(dbg) {
+    if (matchWorkerDebugger(dbg, this._options)) {
+      this._notifyListChanged();
+    }
+  },
+
+  onUnregister(dbg) {
+    if (matchWorkerDebugger(dbg, this._options)) {
+      this._notifyListChanged();
+    }
+  }
+};
+
+exports.WorkerActorList = WorkerActorList;
+
+let PushSubscriptionActor = protocol.ActorClassWithSpec(pushSubscriptionSpec, {
+  initialize(conn, subscription) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this._subscription = subscription;
+  },
+
+  form(detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+    let subscription = this._subscription;
+    return {
+      actor: this.actorID,
+      endpoint: subscription.endpoint,
+      pushCount: subscription.pushCount,
+      lastPush: subscription.lastPush,
+      quota: subscription.quota
+    };
+  },
+
+  destroy() {
+    protocol.Actor.prototype.destroy.call(this);
+    this._subscription = null;
+  },
+});
+
+let ServiceWorkerActor = protocol.ActorClassWithSpec(serviceWorkerSpec, {
+  initialize(conn, worker) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this._worker = worker;
+  },
+
+  form() {
+    if (!this._worker) {
+      return null;
+    }
+
+    return {
+      url: this._worker.scriptSpec,
+      state: this._worker.state,
+    };
+  },
+
+  destroy() {
+    protocol.Actor.prototype.destroy.call(this);
+    this._worker = null;
+  },
+});
+
+// Lazily load the service-worker-child.js process script only once.
+let _serviceWorkerProcessScriptLoaded = false;
+
+let ServiceWorkerRegistrationActor =
+protocol.ActorClassWithSpec(serviceWorkerRegistrationSpec, {
+  /**
+   * Create the ServiceWorkerRegistrationActor
+   * @param DebuggerServerConnection conn
+   *   The server connection.
+   * @param ServiceWorkerRegistrationInfo registration
+   *   The registration's information.
+   */
+  initialize(conn, registration) {
+    protocol.Actor.prototype.initialize.call(this, conn);
+    this._conn = conn;
+    this._registration = registration;
+    this._pushSubscriptionActor = null;
+    this._registration.addListener(this);
+
+    let {installingWorker, waitingWorker, activeWorker} = registration;
+    this._installingWorker = new ServiceWorkerActor(conn, installingWorker);
+    this._waitingWorker = new ServiceWorkerActor(conn, waitingWorker);
+    this._activeWorker = new ServiceWorkerActor(conn, activeWorker);
+
+    Services.obs.addObserver(this, PushService.subscriptionModifiedTopic, false);
+  },
+
+  onChange() {
+    this._installingWorker.destroy();
+    this._waitingWorker.destroy();
+    this._activeWorker.destroy();
+
+    let {installingWorker, waitingWorker, activeWorker} = this._registration;
+    this._installingWorker = new ServiceWorkerActor(this._conn, installingWorker);
+    this._waitingWorker = new ServiceWorkerActor(this._conn, waitingWorker);
+    this._activeWorker = new ServiceWorkerActor(this._conn, activeWorker);
+
+    events.emit(this, "registration-changed");
+  },
+
+  form(detail) {
+    if (detail === "actorid") {
+      return this.actorID;
+    }
+    let registration = this._registration;
+    let installingWorker = this._installingWorker.form();
+    let waitingWorker = this._waitingWorker.form();
+    let activeWorker = this._activeWorker.form();
+
+    let isE10s = Services.appinfo.browserTabsRemoteAutostart;
+    return {
+      actor: this.actorID,
+      scope: registration.scope,
+      url: registration.scriptSpec,
+      installingWorker,
+      waitingWorker,
+      activeWorker,
+      // - In e10s: only active registrations are available.
+      // - In non-e10s: registrations always have at least one worker, if the worker is
+      // active, the registration is active.
+      active: isE10s ? true : !!activeWorker
+    };
+  },
+
+  destroy() {
+    protocol.Actor.prototype.destroy.call(this);
+    Services.obs.removeObserver(this, PushService.subscriptionModifiedTopic, false);
+    this._registration.removeListener(this);
+    this._registration = null;
+    if (this._pushSubscriptionActor) {
+      this._pushSubscriptionActor.destroy();
+    }
+    this._pushSubscriptionActor = null;
+
+    this._installingWorker.destroy();
+    this._waitingWorker.destroy();
+    this._activeWorker.destroy();
+
+    this._installingWorker = null;
+    this._waitingWorker = null;
+    this._activeWorker = null;
+  },
+
+  disconnect() {
+    this.destroy();
+  },
+
+  /**
+   * Standard observer interface to listen to push messages and changes.
+   */
+  observe(subject, topic, data) {
+    let scope = this._registration.scope;
+    if (data !== scope) {
+      // This event doesn't concern us, pretend nothing happened.
+      return;
+    }
+    switch (topic) {
+      case PushService.subscriptionModifiedTopic:
+        if (this._pushSubscriptionActor) {
+          this._pushSubscriptionActor.destroy();
+          this._pushSubscriptionActor = null;
+        }
+        events.emit(this, "push-subscription-modified");
+        break;
+    }
+  },
+
+  start() {
+    if (!_serviceWorkerProcessScriptLoaded) {
+      Services.ppmm.loadProcessScript(
+        "resource://devtools/server/service-worker-child.js", true);
+      _serviceWorkerProcessScriptLoaded = true;
+    }
+    Services.ppmm.broadcastAsyncMessage("serviceWorkerRegistration:start", {
+      scope: this._registration.scope
+    });
+    return { type: "started" };
+  },
+
+  unregister() {
+    let { principal, scope } = this._registration;
+    let unregisterCallback = {
+      unregisterSucceeded: function () {},
+      unregisterFailed: function () {
+        console.error("Failed to unregister the service worker for " + scope);
+      },
+      QueryInterface: XPCOMUtils.generateQI(
+        [Ci.nsIServiceWorkerUnregisterCallback])
+    };
+    swm.propagateUnregister(principal, unregisterCallback, scope);
+
+    return { type: "unregistered" };
+  },
+
+  getPushSubscription() {
+    let registration = this._registration;
+    let pushSubscriptionActor = this._pushSubscriptionActor;
+    if (pushSubscriptionActor) {
+      return Promise.resolve(pushSubscriptionActor);
+    }
+    return new Promise((resolve, reject) => {
+      PushService.getSubscription(
+        registration.scope,
+        registration.principal,
+        (result, subscription) => {
+          if (!subscription) {
+            resolve(null);
+            return;
+          }
+          pushSubscriptionActor = new PushSubscriptionActor(this._conn, subscription);
+          this._pushSubscriptionActor = pushSubscriptionActor;
+          resolve(pushSubscriptionActor);
+        }
+      );
+    });
+  },
+});
+
+function ServiceWorkerRegistrationActorList(conn) {
+  this._conn = conn;
+  this._actors = new Map();
+  this._onListChanged = null;
+  this._mustNotify = false;
+  this.onRegister = this.onRegister.bind(this);
+  this.onUnregister = this.onUnregister.bind(this);
+}
+
+ServiceWorkerRegistrationActorList.prototype = {
+  getList() {
+    // Create a set of registrations.
+    let registrations = new Set();
+    let array = swm.getAllRegistrations();
+    for (let index = 0; index < array.length; ++index) {
+      registrations.add(
+        array.queryElementAt(index, Ci.nsIServiceWorkerRegistrationInfo));
+    }
+
+    // Delete each actor for which we don't have a registration.
+    for (let [registration, ] of this._actors) {
+      if (!registrations.has(registration)) {
+        this._actors.delete(registration);
+      }
+    }
+
+    // Create an actor for each registration for which we don't have one.
+    for (let registration of registrations) {
+      if (!this._actors.has(registration)) {
+        this._actors.set(registration,
+          new ServiceWorkerRegistrationActor(this._conn, registration));
+      }
+    }
+
+    if (!this._mustNotify) {
+      if (this._onListChanged !== null) {
+        swm.addListener(this);
+      }
+      this._mustNotify = true;
+    }
+
+    let actors = [];
+    for (let [, actor] of this._actors) {
+      actors.push(actor);
+    }
+
+    return Promise.resolve(actors);
+  },
+
+  get onListchanged() {
+    return this._onListchanged;
+  },
+
+  set onListChanged(onListChanged) {
+    if (typeof onListChanged !== "function" && onListChanged !== null) {
+      throw new Error("onListChanged must be either a function or null.");
+    }
+
+    if (this._mustNotify) {
+      if (this._onListChanged === null && onListChanged !== null) {
+        swm.addListener(this);
+      }
+      if (this._onListChanged !== null && onListChanged === null) {
+        swm.removeListener(this);
+      }
+    }
+    this._onListChanged = onListChanged;
+  },
+
+  _notifyListChanged() {
+    this._onListChanged();
+
+    if (this._onListChanged !== null) {
+      swm.removeListener(this);
+    }
+    this._mustNotify = false;
+  },
+
+  onRegister(registration) {
+    this._notifyListChanged();
+  },
+
+  onUnregister(registration) {
+    this._notifyListChanged();
+  }
+};
+
+exports.ServiceWorkerRegistrationActorList = ServiceWorkerRegistrationActorList;