Add m-esr52 at 52.6.0

1 files changed, 3186 insertions, 0 deletions

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);
+});