Add m-esr52 at 52.6.0

7 files changed, 1751 insertions, 0 deletions

diff --git a/testing/mochitest/BrowserTestUtils/BrowserTestUtils.jsm b/testing/mochitest/BrowserTestUtils/BrowserTestUtils.jsm
new file mode 100644
index 000000000..eebcbb6bb
--- /dev/null
+++ b/testing/mochitest/BrowserTestUtils/BrowserTestUtils.jsm
@@ -0,0 +1,1329 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * This module implements a number of utilities useful for browser tests.
+ *
+ * All asynchronous helper methods should return promises, rather than being
+ * callback based.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "BrowserTestUtils",
+];
+
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+
+Cu.import("resource://gre/modules/AppConstants.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/Task.jsm");
+Cu.import("resource://gre/modules/Timer.jsm");
+Cu.import("resource://testing-common/TestUtils.jsm");
+Cu.import("resource://testing-common/ContentTask.jsm");
+
+Cc["@mozilla.org/globalmessagemanager;1"]
+  .getService(Ci.nsIMessageListenerManager)
+  .loadFrameScript(
+    "chrome://mochikit/content/tests/BrowserTestUtils/content-utils.js", true);
+
+XPCOMUtils.defineLazyModuleGetter(this, "E10SUtils",
+  "resource:///modules/E10SUtils.jsm");
+
+// For now, we'll allow tests to use CPOWs in this module for
+// some cases.
+Cu.permitCPOWsInScope(this);
+
+var gSendCharCount = 0;
+var gSynthesizeKeyCount = 0;
+var gSynthesizeCompositionCount = 0;
+var gSynthesizeCompositionChangeCount = 0;
+
+const kAboutPageRegistrationContentScript =
+  "chrome://mochikit/content/tests/BrowserTestUtils/content-about-page-utils.js";
+
+this.BrowserTestUtils = {
+  /**
+   * Loads a page in a new tab, executes a Task and closes the tab.
+   *
+   * @param options
+   *        An object  or string.
+   *        If this is a string it is the url to open and will be opened in the
+   *        currently active browser window.
+   *        If an object it should have the following properties:
+   *        {
+   *          gBrowser:
+   *            Reference to the "tabbrowser" element where the new tab should
+   *            be opened.
+   *          url:
+   *            String with the URL of the page to load.
+   *        }
+   * @param taskFn
+   *        Generator function representing a Task that will be executed while
+   *        the tab is loaded. The first argument passed to the function is a
+   *        reference to the browser object for the new tab.
+   *
+   * @return {} Returns the value that is returned from taskFn.
+   * @resolves When the tab has been closed.
+   * @rejects Any exception from taskFn is propagated.
+   */
+  withNewTab: Task.async(function* (options, taskFn) {
+    if (typeof(options) == "string") {
+      options = {
+        gBrowser: Services.wm.getMostRecentWindow("navigator:browser").gBrowser,
+        url: options
+      }
+    }
+    let tab = yield BrowserTestUtils.openNewForegroundTab(options.gBrowser, options.url);
+    let originalWindow = tab.ownerDocument.defaultView;
+    let result = yield taskFn(tab.linkedBrowser);
+    let finalWindow = tab.ownerDocument.defaultView;
+    if (originalWindow == finalWindow && !tab.closing && tab.linkedBrowser) {
+      yield BrowserTestUtils.removeTab(tab);
+    } else {
+      Services.console.logStringMessage(
+        "BrowserTestUtils.withNewTab: Tab was already closed before " +
+        "removeTab would have been called");
+    }
+    return Promise.resolve(result);
+  }),
+
+  /**
+   * Opens a new tab in the foreground.
+   *
+   * @param {tabbrowser} tabbrowser
+   *        The tabbrowser to open the tab new in.
+   * @param {string} opening
+   *        May be either a string URL to load in the tab, or a function that
+   *        will be called to open a foreground tab. Defaults to "about:blank".
+   * @param {boolean} waitForLoad
+   *        True to wait for the page in the new tab to load. Defaults to true.
+   * @param {boolean} waitForStateStop
+   *        True to wait for the web progress listener to send STATE_STOP for the
+   *        document in the tab. Defaults to false.
+   *
+   * @return {Promise}
+   *         Resolves when the tab is ready and loaded as necessary.
+   * @resolves The new tab.
+   */
+  openNewForegroundTab(tabbrowser, opening = "about:blank", aWaitForLoad = true, aWaitForStateStop = false) {
+    let tab;
+    let promises = [
+      BrowserTestUtils.switchTab(tabbrowser, function () {
+        if (typeof opening == "function") {
+          opening();
+          tab = tabbrowser.selectedTab;
+        }
+        else {
+          tabbrowser.selectedTab = tab = tabbrowser.addTab(opening);
+        }
+      })
+    ];
+
+    if (aWaitForLoad) {
+      promises.push(BrowserTestUtils.browserLoaded(tab.linkedBrowser));
+    }
+    if (aWaitForStateStop) {
+      promises.push(BrowserTestUtils.browserStopped(tab.linkedBrowser));
+    }
+
+    return Promise.all(promises).then(() => tab);
+  },
+
+  /**
+   * Switches to a tab and resolves when it is ready.
+   *
+   * @param {tabbrowser} tabbrowser
+   *        The tabbrowser.
+   * @param {tab} tab
+   *        Either a tab element to switch to or a function to perform the switch.
+   *
+   * @return {Promise}
+   *         Resolves when the tab has been switched to.
+   * @resolves The tab switched to.
+   */
+  switchTab(tabbrowser, tab) {
+    let promise = new Promise(resolve => {
+      tabbrowser.addEventListener("TabSwitchDone", function onSwitch() {
+        tabbrowser.removeEventListener("TabSwitchDone", onSwitch);
+        TestUtils.executeSoon(() => resolve(tabbrowser.selectedTab));
+      });
+    });
+
+    if (typeof tab == "function") {
+      tab();
+    }
+    else {
+      tabbrowser.selectedTab = tab;
+    }
+    return promise;
+  },
+
+  /**
+   * Waits for an ongoing page load in a browser window to complete.
+   *
+   * This can be used in conjunction with any synchronous method for starting a
+   * load, like the "addTab" method on "tabbrowser", and must be called before
+   * yielding control to the event loop. This is guaranteed to work because the
+   * way we're listening for the load is in the content-utils.js frame script,
+   * and then sending an async message up, so we can't miss the message.
+   *
+   * @param {xul:browser} browser
+   *        A xul:browser.
+   * @param {Boolean} includeSubFrames
+   *        A boolean indicating if loads from subframes should be included.
+   * @param {optional string or function} wantLoad
+   *        If a function, takes a URL and returns true if that's the load we're
+   *        interested in. If a string, gives the URL of the load we're interested
+   *        in. If not present, the first load resolves the promise.
+   *
+   * @return {Promise}
+   * @resolves When a load event is triggered for the browser.
+   */
+  browserLoaded(browser, includeSubFrames=false, wantLoad=null) {
+    function isWanted(url) {
+      if (!wantLoad) {
+        return true;
+      } else if (typeof(wantLoad) == "function") {
+        return wantLoad(url);
+      } else {
+        // It's a string.
+        return wantLoad == url;
+      }
+    }
+
+    return new Promise(resolve => {
+      let mm = browser.ownerDocument.defaultView.messageManager;
+      mm.addMessageListener("browser-test-utils:loadEvent", function onLoad(msg) {
+        if (msg.target == browser && (!msg.data.subframe || includeSubFrames) &&
+            isWanted(msg.data.url)) {
+          mm.removeMessageListener("browser-test-utils:loadEvent", onLoad);
+          resolve(msg.data.url);
+        }
+      });
+    });
+  },
+
+  /**
+   * Waits for the selected browser to load in a new window. This
+   * is most useful when you've got a window that might not have
+   * loaded its DOM yet, and where you can't easily use browserLoaded
+   * on gBrowser.selectedBrowser since gBrowser doesn't yet exist.
+   *
+   * @param {win}
+   *        A newly opened window for which we're waiting for the
+   *        first browser load.
+   *
+   * @return {Promise}
+   * @resolves Once the selected browser fires its load event.
+   */
+  firstBrowserLoaded(win, aboutBlank = true) {
+    let mm = win.messageManager;
+    return this.waitForMessage(mm, "browser-test-utils:loadEvent", (msg) => {
+      let selectedBrowser = win.gBrowser.selectedBrowser;
+      return msg.target == selectedBrowser &&
+             (aboutBlank || selectedBrowser.currentURI.spec != "about:blank")
+    });
+  },
+
+  /**
+   * Waits for the web progress listener associated with this tab to fire a
+   * STATE_STOP for the toplevel document.
+   *
+   * @param {xul:browser} browser
+   *        A xul:browser.
+   *
+   * @return {Promise}
+   * @resolves When STATE_STOP reaches the tab's progress listener
+   */
+  browserStopped(browser) {
+    return new Promise(resolve => {
+      let wpl = {
+        onStateChange(aWebProgress, aRequest, aStateFlags, aStatus) {
+          if (aStateFlags & Ci.nsIWebProgressListener.STATE_STOP &&
+              aWebProgress.isTopLevel) {
+            browser.webProgress.removeProgressListener(filter);
+            filter.removeProgressListener(wpl);
+            resolve();
+          };
+        },
+        onSecurityChange() {},
+        onStatusChange() {},
+        onLocationChange() {},
+        QueryInterface: XPCOMUtils.generateQI([
+          Ci.nsIWebProgressListener,
+          Ci.nsIWebProgressListener2,
+        ]),
+      };
+      const filter = Cc["@mozilla.org/appshell/component/browser-status-filter;1"]
+                       .createInstance(Ci.nsIWebProgress);
+      filter.addProgressListener(wpl, Ci.nsIWebProgress.NOTIFY_ALL);
+      browser.webProgress.addProgressListener(filter, Ci.nsIWebProgress.NOTIFY_ALL);
+    });
+  },
+
+  /**
+   * Waits for the next tab to open and load a given URL.
+   *
+   * The method doesn't wait for the tab contents to load.
+   *
+   * @param {tabbrowser} tabbrowser
+   *        The tabbrowser to look for the next new tab in.
+   * @param {string} url
+   *        A string URL to look for in the new tab. If null, allows any non-blank URL.
+   *
+   * @return {Promise}
+   * @resolves With the {xul:tab} when a tab is opened and its location changes to the given URL.
+   *
+   * NB: this method will not work if you open a new tab with e.g. BrowserOpenTab
+   * and the tab does not load a URL, because no onLocationChange will fire.
+   */
+  waitForNewTab(tabbrowser, url) {
+    return new Promise((resolve, reject) => {
+      tabbrowser.tabContainer.addEventListener("TabOpen", function onTabOpen(openEvent) {
+        tabbrowser.tabContainer.removeEventListener("TabOpen", onTabOpen);
+
+        let progressListener = {
+          onLocationChange(aBrowser) {
+            if (aBrowser != openEvent.target.linkedBrowser ||
+                (url && aBrowser.currentURI.spec != url) ||
+                (!url && aBrowser.currentURI.spec == "about:blank")) {
+              return;
+            }
+
+            tabbrowser.removeTabsProgressListener(progressListener);
+            resolve(openEvent.target);
+          },
+        };
+        tabbrowser.addTabsProgressListener(progressListener);
+
+      });
+    });
+  },
+
+  /**
+   * Waits for onLocationChange.
+   *
+   * @param {tabbrowser} tabbrowser
+   *        The tabbrowser to wait for the location change on.
+   * @param {string} url
+   *        The string URL to look for. The URL must match the URL in the
+   *        location bar exactly.
+   * @return {Promise}
+   * @resolves When onLocationChange fires.
+   */
+  waitForLocationChange(tabbrowser, url) {
+    return new Promise((resolve, reject) => {
+      let progressListener = {
+        onLocationChange(aBrowser) {
+          if ((url && aBrowser.currentURI.spec != url) ||
+              (!url && aBrowser.currentURI.spec == "about:blank")) {
+            return;
+          }
+
+          tabbrowser.removeTabsProgressListener(progressListener);
+          resolve();
+        },
+      };
+      tabbrowser.addTabsProgressListener(progressListener);
+    });
+  },
+
+  /**
+   * Waits for the next browser window to open and be fully loaded.
+   *
+   * @param {bool} delayedStartup (optional)
+   *        Whether or not to wait for the browser-delayed-startup-finished
+   *        observer notification before resolving. Defaults to true.
+   * @param {string} initialBrowserLoaded (optional)
+   *        If set, we will wait until the initial browser in the new
+   *        window has loaded a particular page. If unset, the initial
+   *        browser may or may not have finished loading its first page
+   *        when the resulting Promise resolves.
+   * @return {Promise}
+   *         A Promise which resolves the next time that a DOM window
+   *         opens and the delayed startup observer notification fires.
+   */
+  waitForNewWindow: Task.async(function* (delayedStartup=true,
+                                          initialBrowserLoaded=null) {
+    let win = yield this.domWindowOpened();
+
+    let promises = [
+      TestUtils.topicObserved("browser-delayed-startup-finished",
+                              subject => subject == win),
+    ];
+
+    if (initialBrowserLoaded) {
+      yield this.waitForEvent(win, "DOMContentLoaded");
+
+      let browser = win.gBrowser.selectedBrowser;
+
+      // Retrieve the given browser's current process type.
+      let process =
+        browser.isRemoteBrowser ? Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT
+                                : Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+      if (win.gMultiProcessBrowser &&
+          !E10SUtils.canLoadURIInProcess(initialBrowserLoaded, process)) {
+        yield this.waitForEvent(browser, "XULFrameLoaderCreated");
+      }
+
+      let loadPromise = this.browserLoaded(browser, false, initialBrowserLoaded);
+      promises.push(loadPromise);
+    }
+
+    yield Promise.all(promises);
+
+    return win;
+  }),
+
+  /**
+   * Loads a new URI in the given browser and waits until we really started
+   * loading. In e10s browser.loadURI() can be an asynchronous operation due
+   * to having to switch the browser's remoteness and keep its shistory data.
+   *
+   * @param {xul:browser} browser
+   *        A xul:browser.
+   * @param {string} uri
+   *        The URI to load.
+   *
+   * @return {Promise}
+   * @resolves When we started loading the given URI.
+   */
+  loadURI: Task.async(function* (browser, uri) {
+    // Load the new URI.
+    browser.loadURI(uri);
+
+    // Nothing to do in non-e10s mode.
+    if (!browser.ownerDocument.defaultView.gMultiProcessBrowser) {
+      return;
+    }
+
+    // Retrieve the given browser's current process type.
+    let process = browser.isRemoteBrowser ? Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT
+                                          : Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+
+    // If the new URI can't load in the browser's current process then we
+    // should wait for the new frameLoader to be created. This will happen
+    // asynchronously when the browser's remoteness changes.
+    if (!E10SUtils.canLoadURIInProcess(uri, process)) {
+      yield this.waitForEvent(browser, "XULFrameLoaderCreated");
+    }
+  }),
+
+  /**
+   * @param win (optional)
+   *        The window we should wait to have "domwindowopened" sent through
+   *        the observer service for. If this is not supplied, we'll just
+   *        resolve when the first "domwindowopened" notification is seen.
+   * @param {function} checkFn [optional]
+   *        Called with the nsIDOMWindow object as argument, should return true
+   *        if the event is the expected one, or false if it should be ignored
+   *        and observing should continue. If not specified, the first window
+   *        resolves the returned promise.
+   * @return {Promise}
+   *         A Promise which resolves when a "domwindowopened" notification
+   *         has been fired by the window watcher.
+   */
+  domWindowOpened(win, checkFn) {
+    return new Promise(resolve => {
+      function observer(subject, topic, data) {
+        if (topic == "domwindowopened" && (!win || subject === win)) {
+          let observedWindow = subject.QueryInterface(Ci.nsIDOMWindow);
+          if (checkFn && !checkFn(observedWindow)) {
+            return;
+          }
+          Services.ww.unregisterNotification(observer);
+          resolve(observedWindow);
+        }
+      }
+      Services.ww.registerNotification(observer);
+    });
+  },
+
+  /**
+   * @param win (optional)
+   *        The window we should wait to have "domwindowclosed" sent through
+   *        the observer service for. If this is not supplied, we'll just
+   *        resolve when the first "domwindowclosed" notification is seen.
+   * @return {Promise}
+   *         A Promise which resolves when a "domwindowclosed" notification
+   *         has been fired by the window watcher.
+   */
+  domWindowClosed(win) {
+    return new Promise((resolve) => {
+      function observer(subject, topic, data) {
+        if (topic == "domwindowclosed" && (!win || subject === win)) {
+          Services.ww.unregisterNotification(observer);
+          resolve(subject.QueryInterface(Ci.nsIDOMWindow));
+        }
+      }
+      Services.ww.registerNotification(observer);
+    });
+  },
+
+  /**
+   * @param {Object} options
+   *        {
+   *          private: A boolean indicating if the window should be
+   *                   private
+   *          remote:  A boolean indicating if the window should run
+   *                   remote browser tabs or not. If omitted, the window
+   *                   will choose the profile default state.
+   *          width: Desired width of window
+   *          height: Desired height of window
+   *        }
+   * @return {Promise}
+   *         Resolves with the new window once it is loaded.
+   */
+  openNewBrowserWindow: Task.async(function*(options={}) {
+    let argString = Cc["@mozilla.org/supports-string;1"].
+                    createInstance(Ci.nsISupportsString);
+    argString.data = "";
+    let features = "chrome,dialog=no,all";
+
+    if (options.private) {
+      features += ",private";
+    }
+
+    if (options.width) {
+      features += ",width=" + options.width;
+    }
+    if (options.height) {
+      features += ",height=" + options.height;
+    }
+
+    if (options.hasOwnProperty("remote")) {
+      let remoteState = options.remote ? "remote" : "non-remote";
+      features += `,${remoteState}`;
+    }
+
+    let win = Services.ww.openWindow(
+      null, Services.prefs.getCharPref("browser.chromeURL"), "_blank",
+      features, argString);
+
+    // Wait for browser-delayed-startup-finished notification, it indicates
+    // that the window has loaded completely and is ready to be used for
+    // testing.
+    let startupPromise =
+      TestUtils.topicObserved("browser-delayed-startup-finished",
+                              subject => subject == win).then(() => win);
+
+    let loadPromise = this.firstBrowserLoaded(win);
+
+    yield startupPromise;
+    yield loadPromise;
+
+    return win;
+  }),
+
+  /**
+   * Closes a window.
+   *
+   * @param {Window}
+   *        A window to close.
+   *
+   * @return {Promise}
+   *         Resolves when the provided window has been closed. For browser
+   *         windows, the Promise will also wait until all final SessionStore
+   *         messages have been sent up from all browser tabs.
+   */
+  closeWindow(win) {
+    let closedPromise = BrowserTestUtils.windowClosed(win);
+    win.close();
+    return closedPromise;
+  },
+
+  /**
+   * Returns a Promise that resolves when a window has finished closing.
+   *
+   * @param {Window}
+   *        The closing window.
+   *
+   * @return {Promise}
+   *        Resolves when the provided window has been fully closed. For
+   *        browser windows, the Promise will also wait until all final
+   *        SessionStore messages have been sent up from all browser tabs.
+   */
+  windowClosed(win)  {
+    let domWinClosedPromise = BrowserTestUtils.domWindowClosed(win);
+    let promises = [domWinClosedPromise];
+    let winType = win.document.documentElement.getAttribute("windowtype");
+
+    if (winType == "navigator:browser") {
+      let finalMsgsPromise = new Promise((resolve) => {
+        let browserSet = new Set(win.gBrowser.browsers);
+        let mm = win.getGroupMessageManager("browsers");
+
+        mm.addMessageListener("SessionStore:update", function onMessage(msg) {
+          if (browserSet.has(msg.target) && msg.data.isFinal) {
+            browserSet.delete(msg.target);
+            if (!browserSet.size) {
+              mm.removeMessageListener("SessionStore:update", onMessage);
+              // Give the TabStateFlusher a chance to react to this final
+              // update and for the TabStateFlusher.flushWindow promise
+              // to resolve before we resolve.
+              TestUtils.executeSoon(resolve);
+            }
+          }
+        }, true);
+      });
+
+      promises.push(finalMsgsPromise);
+    }
+
+    return Promise.all(promises);
+  },
+
+  /**
+   * Waits for an event to be fired on a specified element.
+   *
+   * Usage:
+   *    let promiseEvent = BrowserTestUtils.waitForEvent(element, "eventName");
+   *    // Do some processing here that will cause the event to be fired
+   *    // ...
+   *    // Now yield until the Promise is fulfilled
+   *    let receivedEvent = yield promiseEvent;
+   *
+   * @param {Element} subject
+   *        The element that should receive the event.
+   * @param {string} eventName
+   *        Name of the event to listen to.
+   * @param {bool} capture [optional]
+   *        True to use a capturing listener.
+   * @param {function} checkFn [optional]
+   *        Called with the Event object as argument, should return true if the
+   *        event is the expected one, or false if it should be ignored and
+   *        listening should continue. If not specified, the first event with
+   *        the specified name resolves the returned promise.
+   * @param {bool} wantsUntrusted [optional]
+   *        True to receive synthetic events dispatched by web content.
+   *
+   * @note Because this function is intended for testing, any error in checkFn
+   *       will cause the returned promise to be rejected instead of waiting for
+   *       the next event, since this is probably a bug in the test.
+   *
+   * @returns {Promise}
+   * @resolves The Event object.
+   */
+  waitForEvent(subject, eventName, capture, checkFn, wantsUntrusted) {
+    return new Promise((resolve, reject) => {
+      subject.addEventListener(eventName, function listener(event) {
+        try {
+          if (checkFn && !checkFn(event)) {
+            return;
+          }
+          subject.removeEventListener(eventName, listener, capture);
+          resolve(event);
+        } catch (ex) {
+          try {
+            subject.removeEventListener(eventName, listener, capture);
+          } catch (ex2) {
+            // Maybe the provided object does not support removeEventListener.
+          }
+          reject(ex);
+        }
+      }, capture, wantsUntrusted);
+    });
+  },
+
+  /**
+   * Like waitForEvent, but adds the event listener to the message manager
+   * global for browser.
+   *
+   * @param {string} eventName
+   *        Name of the event to listen to.
+   * @param {bool} capture [optional]
+   *        Whether to use a capturing listener.
+   * @param {function} checkFn [optional]
+   *        Called with the Event object as argument, should return true if the
+   *        event is the expected one, or false if it should be ignored and
+   *        listening should continue. If not specified, the first event with
+   *        the specified name resolves the returned promise.
+   * @param {bool} wantsUntrusted [optional]
+   *        Whether to accept untrusted events
+   *
+   * @note Because this function is intended for testing, any error in checkFn
+   *       will cause the returned promise to be rejected instead of waiting for
+   *       the next event, since this is probably a bug in the test.
+   *
+   * @returns {Promise}
+   */
+  waitForContentEvent(browser, eventName, capture = false, checkFn, wantsUntrusted = false) {
+    let parameters = {
+      eventName,
+      capture,
+      checkFnSource: checkFn ? checkFn.toSource() : null,
+      wantsUntrusted,
+    };
+    return ContentTask.spawn(browser, parameters,
+        function({ eventName, capture, checkFnSource, wantsUntrusted }) {
+          let checkFn;
+          if (checkFnSource) {
+            checkFn = eval(`(() => (${checkFnSource}))()`);
+          }
+          return new Promise((resolve, reject) => {
+            addEventListener(eventName, function listener(event) {
+              let completion = resolve;
+              try {
+                if (checkFn && !checkFn(event)) {
+                  return;
+                }
+              } catch (e) {
+                completion = () => reject(e);
+              }
+              removeEventListener(eventName, listener, capture);
+              completion();
+            }, capture, wantsUntrusted);
+          });
+        });
+  },
+
+  /**
+   * Like browserLoaded, but waits for an error page to appear.
+   * This explicitly deals with cases where the browser is not currently remote and a
+   * remoteness switch will occur before the error page is loaded, which is tricky
+   * because error pages don't fire 'regular' load events that we can rely on.
+   *
+   * @param {xul:browser} browser
+   *        A xul:browser.
+   *
+   * @return {Promise}
+   * @resolves When an error page has been loaded in the browser.
+   */
+  waitForErrorPage(browser) {
+    let waitForLoad = () =>
+      this.waitForContentEvent(browser, "AboutNetErrorLoad", false, null, true);
+
+    let win = browser.ownerDocument.defaultView;
+    let tab = win.gBrowser.getTabForBrowser(browser);
+    if (!tab || browser.isRemoteBrowser || !win.gMultiProcessBrowser) {
+      return waitForLoad();
+    }
+
+    // We're going to switch remoteness when loading an error page. We need to be
+    // quite careful in order to make sure we're adding the listener in time to
+    // get this event:
+    return new Promise((resolve, reject) => {
+      tab.addEventListener("TabRemotenessChange", function onTRC() {
+        tab.removeEventListener("TabRemotenessChange", onTRC);
+        waitForLoad().then(resolve, reject);
+      });
+    });
+  },
+
+  /**
+   *  Versions of EventUtils.jsm synthesizeMouse functions that synthesize a
+   *  mouse event in a child process and return promises that resolve when the
+   *  event has fired and completed. Instead of a window, a browser is required
+   *  to be passed to this function.
+   *
+   * @param target
+   *        One of the following:
+   *        - a selector string that identifies the element to target. The syntax is as
+   *        for querySelector.
+   *        - a CPOW element (for easier test-conversion).
+   *        - a function to be run in the content process that returns the element to
+   *        target
+   *        - null, in which case the offset is from the content document's edge.
+   * @param {integer} offsetX
+   *        x offset from target's left bounding edge
+   * @param {integer} offsetY
+   *        y offset from target's top bounding edge
+   * @param {Object} event object
+   *        Additional arguments, similar to the EventUtils.jsm version
+   * @param {Browser} browser
+   *        Browser element, must not be null
+   *
+   * @returns {Promise}
+   * @resolves True if the mouse event was cancelled.
+   */
+  synthesizeMouse(target, offsetX, offsetY, event, browser)
+  {
+    return new Promise((resolve, reject) => {
+      let mm = browser.messageManager;
+      mm.addMessageListener("Test:SynthesizeMouseDone", function mouseMsg(message) {
+        mm.removeMessageListener("Test:SynthesizeMouseDone", mouseMsg);
+        if (message.data.hasOwnProperty("defaultPrevented")) {
+          resolve(message.data.defaultPrevented);
+        } else {
+          reject(new Error(message.data.error));
+        }
+      });
+
+      let cpowObject = null;
+      let targetFn = null;
+      if (typeof target == "function") {
+        targetFn = target.toString();
+        target = null;
+      } else if (typeof target != "string") {
+        cpowObject = target;
+        target = null;
+      }
+
+      mm.sendAsyncMessage("Test:SynthesizeMouse",
+                          {target, targetFn, x: offsetX, y: offsetY, event: event},
+                          {object: cpowObject});
+    });
+  },
+
+  /**
+   * Wait for a message to be fired from a particular message manager
+   *
+   * @param {nsIMessageManager} messageManager
+   *                            The message manager that should be used.
+   * @param {String}            message
+   *                            The message we're waiting for.
+   * @param {Function}          checkFn (optional)
+   *                            Optional function to invoke to check the message.
+   */
+  waitForMessage(messageManager, message, checkFn) {
+    return new Promise(resolve => {
+      messageManager.addMessageListener(message, function onMessage(msg) {
+        if (!checkFn || checkFn(msg)) {
+          messageManager.removeMessageListener(message, onMessage);
+          resolve();
+        }
+      });
+    });
+  },
+
+  /**
+   *  Version of synthesizeMouse that uses the center of the target as the mouse
+   *  location. Arguments and the return value are the same.
+   */
+  synthesizeMouseAtCenter(target, event, browser)
+  {
+    // Use a flag to indicate to center rather than having a separate message.
+    event.centered = true;
+    return BrowserTestUtils.synthesizeMouse(target, 0, 0, event, browser);
+  },
+
+  /**
+   *  Version of synthesizeMouse that uses a client point within the child
+   *  window instead of a target as the offset. Otherwise, the arguments and
+   *  return value are the same as synthesizeMouse.
+   */
+  synthesizeMouseAtPoint(offsetX, offsetY, event, browser)
+  {
+    return BrowserTestUtils.synthesizeMouse(null, offsetX, offsetY, event, browser);
+  },
+
+  /**
+   * Removes the given tab from its parent tabbrowser and
+   * waits until its final message has reached the parent.
+   */
+  removeTab(tab, options = {}) {
+    let dontRemove = options && options.dontRemove;
+
+    return new Promise(resolve => {
+      let {messageManager: mm, frameLoader} = tab.linkedBrowser;
+      mm.addMessageListener("SessionStore:update", function onMessage(msg) {
+        if (msg.targetFrameLoader == frameLoader && msg.data.isFinal) {
+          mm.removeMessageListener("SessionStore:update", onMessage);
+          resolve();
+        }
+      }, true);
+
+      if (!dontRemove && !tab.closing) {
+        tab.ownerDocument.defaultView.gBrowser.removeTab(tab);
+      }
+    });
+  },
+
+  /**
+   * Crashes a remote browser tab and cleans up the generated minidumps.
+   * Resolves with the data from the .extra file (the crash annotations).
+   *
+   * @param (Browser) browser
+   *        A remote <xul:browser> element. Must not be null.
+   * @param (bool) shouldShowTabCrashPage
+   *        True if it is expected that the tab crashed page will be shown
+   *        for this browser. If so, the Promise will only resolve once the
+   *        tab crash page has loaded.
+   *
+   * @returns (Promise)
+   * @resolves An Object with key-value pairs representing the data from the
+   *           crash report's extra file (if applicable).
+   */
+  crashBrowser: Task.async(function*(browser, shouldShowTabCrashPage=true) {
+    let extra = {};
+    let KeyValueParser = {};
+    if (AppConstants.MOZ_CRASHREPORTER) {
+      Cu.import("resource://gre/modules/KeyValueParser.jsm", KeyValueParser);
+    }
+
+    if (!browser.isRemoteBrowser) {
+      throw new Error("<xul:browser> needs to be remote in order to crash");
+    }
+
+    /**
+     * Returns the directory where crash dumps are stored.
+     *
+     * @return nsIFile
+     */
+    function getMinidumpDirectory() {
+      let dir = Services.dirsvc.get('ProfD', Ci.nsIFile);
+      dir.append("minidumps");
+      return dir;
+    }
+
+    /**
+     * Removes a file from a directory. This is a no-op if the file does not
+     * exist.
+     *
+     * @param directory
+     *        The nsIFile representing the directory to remove from.
+     * @param filename
+     *        A string for the file to remove from the directory.
+     */
+    function removeFile(directory, filename) {
+      let file = directory.clone();
+      file.append(filename);
+      if (file.exists()) {
+        file.remove(false);
+      }
+    }
+
+    // This frame script is injected into the remote browser, and used to
+    // intentionally crash the tab. We crash by using js-ctypes and dereferencing
+    // a bad pointer. The crash should happen immediately upon loading this
+    // frame script.
+    let frame_script = () => {
+      const Cu = Components.utils;
+      Cu.import("resource://gre/modules/ctypes.jsm");
+
+      let dies = function() {
+        privateNoteIntentionalCrash();
+        let zero = new ctypes.intptr_t(8);
+        let badptr = ctypes.cast(zero, ctypes.PointerType(ctypes.int32_t));
+        badptr.contents
+      };
+
+      dump("\nEt tu, Brute?\n");
+      dies();
+    }
+
+    let expectedPromises = [];
+
+    let crashCleanupPromise = new Promise((resolve, reject) => {
+      let observer = (subject, topic, data) => {
+        if (topic != "ipc:content-shutdown") {
+          return reject("Received incorrect observer topic: " + topic);
+        }
+        if (!(subject instanceof Ci.nsIPropertyBag2)) {
+          return reject("Subject did not implement nsIPropertyBag2");
+        }
+        // we might see this called as the process terminates due to previous tests.
+        // We are only looking for "abnormal" exits...
+        if (!subject.hasKey("abnormal")) {
+          dump("\nThis is a normal termination and isn't the one we are looking for...\n");
+          return;
+        }
+
+        let dumpID;
+        if ('nsICrashReporter' in Ci) {
+          dumpID = subject.getPropertyAsAString('dumpID');
+          if (!dumpID) {
+            return reject("dumpID was not present despite crash reporting " +
+                          "being enabled");
+          }
+        }
+
+        if (dumpID) {
+          let minidumpDirectory = getMinidumpDirectory();
+          let extrafile = minidumpDirectory.clone();
+          extrafile.append(dumpID + '.extra');
+          if (extrafile.exists()) {
+            dump(`\nNo .extra file for dumpID: ${dumpID}\n`);
+            if (AppConstants.MOZ_CRASHREPORTER) {
+              extra = KeyValueParser.parseKeyValuePairsFromFile(extrafile);
+            } else {
+              dump('\nCrashReporter not enabled - will not return any extra data\n');
+            }
+          }
+
+          removeFile(minidumpDirectory, dumpID + '.dmp');
+          removeFile(minidumpDirectory, dumpID + '.extra');
+        }
+
+        Services.obs.removeObserver(observer, 'ipc:content-shutdown');
+        dump("\nCrash cleaned up\n");
+        // There might be other ipc:content-shutdown handlers that need to run before
+        // we want to continue, so we'll resolve on the next tick of the event loop.
+        TestUtils.executeSoon(() => resolve());
+      };
+
+      Services.obs.addObserver(observer, 'ipc:content-shutdown', false);
+    });
+
+    expectedPromises.push(crashCleanupPromise);
+
+    if (shouldShowTabCrashPage) {
+      expectedPromises.push(new Promise((resolve, reject) => {
+        browser.addEventListener("AboutTabCrashedReady", function onCrash() {
+          browser.removeEventListener("AboutTabCrashedReady", onCrash, false);
+          dump("\nabout:tabcrashed loaded and ready\n");
+          resolve();
+        }, false, true);
+      }));
+    }
+
+    // This frame script will crash the remote browser as soon as it is
+    // evaluated.
+    let mm = browser.messageManager;
+    mm.loadFrameScript("data:,(" + frame_script.toString() + ")();", false);
+
+    yield Promise.all(expectedPromises);
+
+    if (shouldShowTabCrashPage) {
+      let gBrowser = browser.ownerDocument.defaultView.gBrowser;
+      let tab = gBrowser.getTabForBrowser(browser);
+      if (tab.getAttribute("crashed") != "true") {
+        throw new Error("Tab should be marked as crashed");
+      }
+    }
+
+    return extra;
+  }),
+
+  /**
+   * Returns a promise that is resolved when element gains attribute (or,
+   * optionally, when it is set to value).
+   * @param {String} attr
+   *        The attribute to wait for
+   * @param {Element} element
+   *        The element which should gain the attribute
+   * @param {String} value (optional)
+   *        Optional, the value the attribute should have.
+   *
+   * @returns {Promise}
+   */
+  waitForAttribute(attr, element, value) {
+    let MutationObserver = element.ownerDocument.defaultView.MutationObserver;
+    return new Promise(resolve => {
+      let mut = new MutationObserver(mutations => {
+        if ((!value && element.getAttribute(attr)) ||
+            (value && element.getAttribute(attr) === value)) {
+          resolve();
+          mut.disconnect();
+          return;
+        }
+      });
+
+      mut.observe(element, {attributeFilter: [attr]});
+    });
+  },
+
+  /**
+   * Version of EventUtils' `sendChar` function; it will synthesize a keypress
+   * event in a child process and returns a Promise that will resolve when the
+   * event was fired. Instead of a Window, a Browser object is required to be
+   * passed to this function.
+   *
+   * @param {String} char
+   *        A character for the keypress event that is sent to the browser.
+   * @param {Browser} browser
+   *        Browser element, must not be null.
+   *
+   * @returns {Promise}
+   * @resolves True if the keypress event was synthesized.
+   */
+  sendChar(char, browser) {
+    return new Promise(resolve => {
+      let seq = ++gSendCharCount;
+      let mm = browser.messageManager;
+
+      mm.addMessageListener("Test:SendCharDone", function charMsg(message) {
+        if (message.data.seq != seq)
+          return;
+
+        mm.removeMessageListener("Test:SendCharDone", charMsg);
+        resolve(message.data.result);
+      });
+
+      mm.sendAsyncMessage("Test:SendChar", {
+        char: char,
+        seq: seq
+      });
+    });
+  },
+
+  /**
+   * Version of EventUtils' `synthesizeKey` function; it will synthesize a key
+   * event in a child process and returns a Promise that will resolve when the
+   * event was fired. Instead of a Window, a Browser object is required to be
+   * passed to this function.
+   *
+   * @param {String} key
+   *        See the documentation available for EventUtils#synthesizeKey.
+   * @param {Object} event
+   *        See the documentation available for EventUtils#synthesizeKey.
+   * @param {Browser} browser
+   *        Browser element, must not be null.
+   *
+   * @returns {Promise}
+   */
+  synthesizeKey(key, event, browser) {
+    return new Promise(resolve => {
+      let seq = ++gSynthesizeKeyCount;
+      let mm = browser.messageManager;
+
+      mm.addMessageListener("Test:SynthesizeKeyDone", function keyMsg(message) {
+        if (message.data.seq != seq)
+          return;
+
+        mm.removeMessageListener("Test:SynthesizeKeyDone", keyMsg);
+        resolve();
+      });
+
+      mm.sendAsyncMessage("Test:SynthesizeKey", { key, event, seq });
+    });
+  },
+
+  /**
+   * Version of EventUtils' `synthesizeComposition` function; it will synthesize
+   * a composition event in a child process and returns a Promise that will
+   * resolve when the event was fired. Instead of a Window, a Browser object is
+   * required to be passed to this function.
+   *
+   * @param {Object} event
+   *        See the documentation available for EventUtils#synthesizeComposition.
+   * @param {Browser} browser
+   *        Browser element, must not be null.
+   *
+   * @returns {Promise}
+   * @resolves False if the composition event could not be synthesized.
+   */
+  synthesizeComposition(event, browser) {
+    return new Promise(resolve => {
+      let seq = ++gSynthesizeCompositionCount;
+      let mm = browser.messageManager;
+
+      mm.addMessageListener("Test:SynthesizeCompositionDone", function compMsg(message) {
+        if (message.data.seq != seq)
+          return;
+
+        mm.removeMessageListener("Test:SynthesizeCompositionDone", compMsg);
+        resolve(message.data.result);
+      });
+
+      mm.sendAsyncMessage("Test:SynthesizeComposition", { event, seq });
+    });
+  },
+
+  /**
+   * Version of EventUtils' `synthesizeCompositionChange` function; it will
+   * synthesize a compositionchange event in a child process and returns a
+   * Promise that will resolve when the event was fired. Instead of a Window, a
+   * Browser object is required to be passed to this function.
+   *
+   * @param {Object} event
+   *        See the documentation available for EventUtils#synthesizeCompositionChange.
+   * @param {Browser} browser
+   *        Browser element, must not be null.
+   *
+   * @returns {Promise}
+   */
+  synthesizeCompositionChange(event, browser) {
+    return new Promise(resolve => {
+      let seq = ++gSynthesizeCompositionChangeCount;
+      let mm = browser.messageManager;
+
+      mm.addMessageListener("Test:SynthesizeCompositionChangeDone", function compMsg(message) {
+        if (message.data.seq != seq)
+          return;
+
+        mm.removeMessageListener("Test:SynthesizeCompositionChangeDone", compMsg);
+        resolve();
+      });
+
+      mm.sendAsyncMessage("Test:SynthesizeCompositionChange", { event, seq });
+    });
+  },
+
+  /**
+   * Will poll a condition function until it returns true.
+   *
+   * @param condition
+   *        A condition function that must return true or false. If the
+   *        condition ever throws, this is also treated as a false. The
+   *        function can be a generator.
+   * @param interval
+   *        The time interval to poll the condition function. Defaults
+   *        to 100ms.
+   * @param attempts
+   *        The number of times to poll before giving up and rejecting
+   *        if the condition has not yet returned true. Defaults to 50
+   *        (~5 seconds for 100ms intervals)
+   * @return Promise
+   *        Resolves when condition is true.
+   *        Rejects if timeout is exceeded or condition ever throws.
+   */
+  waitForCondition(condition, msg, interval=100, maxTries=50) {
+    return new Promise((resolve, reject) => {
+      let tries = 0;
+      let intervalID = setInterval(Task.async(function* () {
+        if (tries >= maxTries) {
+          clearInterval(intervalID);
+          msg += ` - timed out after ${maxTries} tries.`;
+          reject(msg);
+          return;
+        }
+
+        let conditionPassed = false;
+        try {
+          conditionPassed = yield condition();
+        } catch(e) {
+          msg += ` - threw exception: ${e}`;
+          clearInterval(intervalID);
+          reject(msg);
+          return;
+        }
+
+        if (conditionPassed) {
+          clearInterval(intervalID);
+          resolve();
+        }
+        tries++;
+      }), interval);
+    });
+  },
+
+  /**
+   * Waits for a <xul:notification> with a particular value to appear
+   * for the <xul:notificationbox> of the passed in browser.
+   *
+   * @param tabbrowser (<xul:tabbrowser>)
+   *        The gBrowser that hosts the browser that should show
+   *        the notification. For most tests, this will probably be
+   *        gBrowser.
+   * @param browser (<xul:browser>)
+   *        The browser that should be showing the notification.
+   * @param notificationValue (string)
+   *        The "value" of the notification, which is often used as
+   *        a unique identifier. Example: "plugin-crashed".
+   * @return Promise
+   *        Resolves to the <xul:notification> that is being shown.
+   */
+  waitForNotificationBar(tabbrowser, browser, notificationValue) {
+    let notificationBox = tabbrowser.getNotificationBox(browser);
+    return this.waitForNotificationInNotificationBox(notificationBox,
+                                                     notificationValue);
+  },
+
+  /**
+   * Waits for a <xul:notification> with a particular value to appear
+   * in the global <xul:notificationbox> of the given browser window.
+   *
+   * @param win (<xul:window>)
+   *        The browser window in whose global notificationbox the
+   *        notification is expected to appear.
+   * @param notificationValue (string)
+   *        The "value" of the notification, which is often used as
+   *        a unique identifier. Example: "captive-portal-detected".
+   * @return Promise
+   *        Resolves to the <xul:notification> that is being shown.
+   */
+  waitForGlobalNotificationBar(win, notificationValue) {
+    let notificationBox =
+      win.document.getElementById("high-priority-global-notificationbox");
+    return this.waitForNotificationInNotificationBox(notificationBox,
+                                                     notificationValue);
+  },
+
+  waitForNotificationInNotificationBox(notificationBox, notificationValue) {
+    return new Promise((resolve) => {
+      let check = (event) => {
+        return event.target.value == notificationValue;
+      };
+
+      BrowserTestUtils.waitForEvent(notificationBox, "AlertActive",
+                                    false, check).then((event) => {
+        // The originalTarget of the AlertActive on a notificationbox
+        // will be the notification itself.
+        resolve(event.originalTarget);
+      });
+    });
+  },
+
+  /**
+   * Returns a Promise that will resolve once MozAfterPaint
+   * has been fired in the content of a browser.
+   *
+   * @param browser (<xul:browser>)
+   *        The browser for which we're waiting for the MozAfterPaint
+   *        event to occur in.
+   * @returns Promise
+   */
+  contentPainted(browser) {
+    return ContentTask.spawn(browser, null, function*() {
+      return new Promise((resolve) => {
+        addEventListener("MozAfterPaint", function onPaint() {
+          removeEventListener("MozAfterPaint", onPaint);
+          resolve();
+        })
+      });
+    });
+  },
+
+  _knownAboutPages: new Set(),
+  _loadedAboutContentScript: false,
+  /**
+   * Registers an about: page with particular flags in both the parent
+   * and any content processes. Returns a promise that resolves when
+   * registration is complete.
+   *
+   * @param registerCleanupFunction (Function)
+   *        The test framework doesn't keep its cleanup stuff anywhere accessible,
+   *        so the first argument is a reference to your cleanup registration
+   *        function, allowing us to clean up after you if necessary.
+   * @param aboutModule (String)
+   *        The name of the about page.
+   * @param pageURI (String)
+   *        The URI the about: page should point to.
+   * @param flags (Number)
+   *        The nsIAboutModule flags to use for registration.
+   * @returns Promise that resolves when registration has finished.
+   */
+  registerAboutPage(registerCleanupFunction, aboutModule, pageURI, flags) {
+    // Return a promise that resolves when registration finished.
+    const kRegistrationMsgId = "browser-test-utils:about-registration:registered";
+    let rv = this.waitForMessage(Services.ppmm, kRegistrationMsgId, msg => {
+      return msg.data == aboutModule;
+    });
+    // Load a script that registers our page, then send it a message to execute the registration.
+    if (!this._loadedAboutContentScript) {
+      Services.ppmm.loadProcessScript(kAboutPageRegistrationContentScript, true);
+      this._loadedAboutContentScript = true;
+      registerCleanupFunction(this._removeAboutPageRegistrations.bind(this));
+    }
+    Services.ppmm.broadcastAsyncMessage("browser-test-utils:about-registration:register",
+                                        {aboutModule, pageURI, flags});
+    return rv.then(() => {
+      this._knownAboutPages.add(aboutModule);
+    });
+  },
+
+  unregisterAboutPage(aboutModule) {
+    if (!this._knownAboutPages.has(aboutModule)) {
+      return Promise.reject(new Error("We don't think this about page exists!"));
+    }
+    const kUnregistrationMsgId = "browser-test-utils:about-registration:unregistered";
+    let rv = this.waitForMessage(Services.ppmm, kUnregistrationMsgId, msg => {
+      return msg.data == aboutModule;
+    });
+    Services.ppmm.broadcastAsyncMessage("browser-test-utils:about-registration:unregister",
+                                        aboutModule);
+    return rv.then(() => this._knownAboutPages.delete(aboutModule));
+  },
+
+  *_removeAboutPageRegistrations() {
+    for (let aboutModule of this._knownAboutPages) {
+      yield this.unregisterAboutPage(aboutModule);
+    }
+    Services.ppmm.removeDelayedProcessScript(kAboutPageRegistrationContentScript);
+  },
+};
diff --git a/testing/mochitest/BrowserTestUtils/ContentTask.jsm b/testing/mochitest/BrowserTestUtils/ContentTask.jsm
new file mode 100644
index 000000000..a52dd90d3
--- /dev/null
+++ b/testing/mochitest/BrowserTestUtils/ContentTask.jsm
@@ -0,0 +1,128 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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";
+
+this.EXPORTED_SYMBOLS = [
+  "ContentTask"
+];
+
+const { classes: Cc, interfaces: Ci, utils: Cu } = Components;
+Cu.import("resource://gre/modules/Promise.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+
+const FRAME_SCRIPT = "chrome://mochikit/content/tests/BrowserTestUtils/content-task.js";
+
+/**
+ * Keeps track of whether the frame script was already loaded.
+ */
+var gFrameScriptLoaded = false;
+
+/**
+ * Mapping from message id to associated promise.
+ */
+var gPromises = new Map();
+
+/**
+ * Incrementing integer to generate unique message id.
+ */
+var gMessageID = 1;
+
+/**
+ * This object provides the public module functions.
+ */
+this.ContentTask = {
+  /**
+   * _testScope saves the current testScope from
+   * browser-test.js. This is used to implement SimpleTest functions
+   * like ok() and is() in the content process. The scope is only
+   * valid for tasks spawned in the current test, so we keep track of
+   * the ID of the first task spawned in this test (_scopeValidId).
+   */
+  _testScope: null,
+  _scopeValidId: 0,
+
+  /**
+   * Creates and starts a new task in a browser's content.
+   *
+   * @param browser A xul:browser
+   * @param arg A single serializable argument that will be passed to the
+   *             task when executed on the content process.
+   * @param task
+   *        - A generator or function which will be serialized and sent to
+   *          the remote browser to be executed. Unlike Task.spawn, this
+   *          argument may not be an iterator as it will be serialized and
+   *          sent to the remote browser.
+   * @return A promise object where you can register completion callbacks to be
+   *         called when the task terminates.
+   * @resolves With the final returned value of the task if it executes
+   *           successfully.
+   * @rejects An error message if execution fails.
+   */
+  spawn: function ContentTask_spawn(browser, arg, task) {
+    // Load the frame script if needed.
+    if (!gFrameScriptLoaded) {
+      Services.mm.loadFrameScript(FRAME_SCRIPT, true);
+      gFrameScriptLoaded = true;
+    }
+
+    let deferred = {};
+    deferred.promise = new Promise((resolve, reject) => {
+      deferred.resolve = resolve;
+      deferred.reject = reject;
+    });
+
+    let id = gMessageID++;
+    gPromises.set(id, deferred);
+
+    browser.messageManager.sendAsyncMessage(
+      "content-task:spawn",
+      {
+        id: id,
+        runnable: task.toString(),
+        arg: arg,
+      });
+
+    return deferred.promise;
+  },
+
+  setTestScope(scope) {
+    this._testScope = scope;
+    this._scopeValidId = gMessageID;
+  },
+};
+
+var ContentMessageListener = {
+  receiveMessage(aMessage) {
+    let id = aMessage.data.id;
+
+    if (id < ContentTask._scopeValidId) {
+      throw new Error("test result returned after test finished");
+    }
+
+    if (aMessage.name == "content-task:complete") {
+      let deferred = gPromises.get(id);
+      gPromises.delete(id);
+
+      if (aMessage.data.error) {
+        deferred.reject(aMessage.data.error);
+      } else {
+        deferred.resolve(aMessage.data.result);
+      }
+    } else if (aMessage.name == "content-task:test-result") {
+      let data = aMessage.data;
+      ContentTask._testScope.ok(data.condition, data.name, null, data.stack);
+    } else if (aMessage.name == "content-task:test-info") {
+      ContentTask._testScope.info(aMessage.data.name);
+    } else if (aMessage.name == "content-task:test-todo") {
+      ContentTask._testScope.todo(aMessage.data.expr, aMessage.data.name);
+    }
+  },
+};
+
+Services.mm.addMessageListener("content-task:complete", ContentMessageListener);
+Services.mm.addMessageListener("content-task:test-result", ContentMessageListener);
+Services.mm.addMessageListener("content-task:test-info", ContentMessageListener);
diff --git a/testing/mochitest/BrowserTestUtils/ContentTaskUtils.jsm b/testing/mochitest/BrowserTestUtils/ContentTaskUtils.jsm
new file mode 100644
index 000000000..27da0de22
--- /dev/null
+++ b/testing/mochitest/BrowserTestUtils/ContentTaskUtils.jsm
@@ -0,0 +1,120 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * This module implements a number of utility functions that can be loaded
+ * into content scope.
+ *
+ * All asynchronous helper methods should return promises, rather than being
+ * callback based.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "ContentTaskUtils",
+];
+
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+
+Cu.import("resource://gre/modules/Timer.jsm");
+
+this.ContentTaskUtils = {
+  /**
+   * Will poll a condition function until it returns true.
+   *
+   * @param condition
+   *        A condition function that must return true or false. If the
+   *        condition ever throws, this is also treated as a false.
+   * @param interval
+   *        The time interval to poll the condition function. Defaults
+   *        to 100ms.
+   * @param attempts
+   *        The number of times to poll before giving up and rejecting
+   *        if the condition has not yet returned true. Defaults to 50
+   *        (~5 seconds for 100ms intervals)
+   * @return Promise
+   *        Resolves when condition is true.
+   *        Rejects if timeout is exceeded or condition ever throws.
+   */
+  waitForCondition(condition, msg, interval=100, maxTries=50) {
+    return new Promise((resolve, reject) => {
+      let tries = 0;
+      let intervalID = setInterval(() => {
+        if (tries >= maxTries) {
+          clearInterval(intervalID);
+          msg += ` - timed out after ${maxTries} tries.`;
+          reject(msg);
+          return;
+        }
+
+        let conditionPassed = false;
+        try {
+          conditionPassed = condition();
+        } catch(e) {
+          msg += ` - threw exception: ${e}`;
+          clearInterval(intervalID);
+          reject(msg);
+          return;
+        }
+
+        if (conditionPassed) {
+          clearInterval(intervalID);
+          resolve();
+        }
+        tries++;
+      }, interval);
+    });
+  },
+
+  /**
+   * Waits for an event to be fired on a specified element.
+   *
+   * Usage:
+   *    let promiseEvent = ContentTasKUtils.waitForEvent(element, "eventName");
+   *    // Do some processing here that will cause the event to be fired
+   *    // ...
+   *    // Now yield until the Promise is fulfilled
+   *    let receivedEvent = yield promiseEvent;
+   *
+   * @param {Element} subject
+   *        The element that should receive the event.
+   * @param {string} eventName
+   *        Name of the event to listen to.
+   * @param {bool} capture [optional]
+   *        True to use a capturing listener.
+   * @param {function} checkFn [optional]
+   *        Called with the Event object as argument, should return true if the
+   *        event is the expected one, or false if it should be ignored and
+   *        listening should continue. If not specified, the first event with
+   *        the specified name resolves the returned promise.
+   *
+   * @note Because this function is intended for testing, any error in checkFn
+   *       will cause the returned promise to be rejected instead of waiting for
+   *       the next event, since this is probably a bug in the test.
+   *
+   * @returns {Promise}
+   * @resolves The Event object.
+   */
+  waitForEvent(subject, eventName, capture, checkFn, wantsUntrusted = false) {
+    return new Promise((resolve, reject) => {
+      subject.addEventListener(eventName, function listener(event) {
+        try {
+          if (checkFn && !checkFn(event)) {
+            return;
+          }
+          subject.removeEventListener(eventName, listener, capture);
+          resolve(event);
+        } catch (ex) {
+          try {
+            subject.removeEventListener(eventName, listener, capture);
+          } catch (ex2) {
+            // Maybe the provided object does not support removeEventListener.
+          }
+          reject(ex);
+        }
+      }, capture, wantsUntrusted);
+    });
+  },
+};
diff --git a/testing/mochitest/BrowserTestUtils/content/content-about-page-utils.js b/testing/mochitest/BrowserTestUtils/content/content-about-page-utils.js
new file mode 100644
index 000000000..974f084ea
--- /dev/null
+++ b/testing/mochitest/BrowserTestUtils/content/content-about-page-utils.js
@@ -0,0 +1,76 @@
+"use strict";
+
+var {classes: Cc, interfaces: Ci, utils: Cu, manager: Cm} = Components;
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+const { generateUUID } = Cc["@mozilla.org/uuid-generator;1"].getService(Ci.nsIUUIDGenerator);
+
+function AboutPage(aboutHost, chromeURL, uriFlags) {
+  this.chromeURL = chromeURL;
+  this.aboutHost = aboutHost;
+  this.classID = Components.ID(generateUUID().number);
+  this.description = "BrowserTestUtils: " + aboutHost;
+  this.uriFlags = uriFlags;
+}
+
+AboutPage.prototype = {
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIAboutModule]),
+  getURIFlags(aURI) { // eslint-disable-line no-unused-vars
+    return this.uriFlags;
+  },
+
+  newChannel(aURI, aLoadInfo) {
+    let newURI = Services.io.newURI(this.chromeURL, null, null);
+    let channel = Services.io.newChannelFromURIWithLoadInfo(newURI,
+                                                            aLoadInfo);
+    channel.originalURI = aURI;
+
+    if (this.uriFlags & Ci.nsIAboutModule.URI_SAFE_FOR_UNTRUSTED_CONTENT) {
+      channel.owner = null;
+    }
+    return channel;
+  },
+
+  createInstance(outer, iid) {
+    if (outer !== null) {
+      throw Cr.NS_ERROR_NO_AGGREGATION;
+    }
+    return this.QueryInterface(iid);
+  },
+
+  register() {
+    Cm.QueryInterface(Ci.nsIComponentRegistrar).registerFactory(
+      this.classID, this.description,
+      "@mozilla.org/network/protocol/about;1?what=" + this.aboutHost, this);
+  },
+
+  unregister() {
+    Cm.QueryInterface(Ci.nsIComponentRegistrar).unregisterFactory(
+      this.classID, this);
+  }
+};
+
+const gRegisteredPages = new Map();
+
+addMessageListener("browser-test-utils:about-registration:register", msg => {
+  let {aboutModule, pageURI, flags} = msg.data;
+  if (gRegisteredPages.has(aboutModule)) {
+    gRegisteredPages.get(aboutModule).unregister();
+  }
+  let moduleObj = new AboutPage(aboutModule, pageURI, flags);
+  moduleObj.register();
+  gRegisteredPages.set(aboutModule, moduleObj);
+  sendAsyncMessage("browser-test-utils:about-registration:registered", aboutModule);
+});
+
+addMessageListener("browser-test-utils:about-registration:unregister", msg => {
+  let aboutModule = msg.data;
+  let moduleObj = gRegisteredPages.get(aboutModule);
+  if (moduleObj) {
+    moduleObj.unregister();
+    gRegisteredPages.delete(aboutModule);
+  }
+  sendAsyncMessage("browser-test-utils:about-registration:unregistered", aboutModule);
+});
diff --git a/testing/mochitest/BrowserTestUtils/content/content-task.js b/testing/mochitest/BrowserTestUtils/content/content-task.js
new file mode 100644
index 000000000..3eb5d3d01
--- /dev/null
+++ b/testing/mochitest/BrowserTestUtils/content/content-task.js
@@ -0,0 +1,71 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+
+Cu.import("resource://gre/modules/Task.jsm", this);
+Cu.import("resource://testing-common/ContentTaskUtils.jsm", this);
+const AssertCls = Cu.import("resource://testing-common/Assert.jsm", null).Assert;
+
+addMessageListener("content-task:spawn", function (msg) {
+  let id = msg.data.id;
+  let source = msg.data.runnable || "()=>{}";
+
+  function getStack(aStack) {
+    let frames = [];
+    for (let frame = aStack; frame; frame = frame.caller) {
+      frames.push(frame.filename + ":" + frame.name + ":" + frame.lineNumber);
+    }
+    return frames.join("\n");
+  }
+
+  var Assert = new AssertCls((err, message, stack) => {
+    sendAsyncMessage("content-task:test-result", {
+      id: id,
+      condition: !err,
+      name: err ? err.message : message,
+      stack: getStack(err ? err.stack : stack)
+    });
+  });
+
+  var ok = Assert.ok.bind(Assert);
+  var is = Assert.equal.bind(Assert);
+  var isnot = Assert.notEqual.bind(Assert);
+
+  function todo(expr, name) {
+    sendAsyncMessage("content-task:test-todo", {id, expr, name});
+  }
+
+  function info(name) {
+    sendAsyncMessage("content-task:test-info", {id, name});
+  }
+
+  try {
+    let runnablestr = `
+      (() => {
+        return (${source});
+      })();`
+
+    let runnable = eval(runnablestr);
+    let iterator = runnable.call(this, msg.data.arg);
+    Task.spawn(iterator).then((val) => {
+      sendAsyncMessage("content-task:complete", {
+        id: id,
+        result: val,
+      });
+    }, (e) => {
+      sendAsyncMessage("content-task:complete", {
+        id: id,
+        error: e.toString(),
+      });
+    });
+  } catch (e) {
+    sendAsyncMessage("content-task:complete", {
+      id: id,
+      error: e.toString(),
+    });
+  }
+});
diff --git a/testing/mochitest/BrowserTestUtils/content/content-utils.js b/testing/mochitest/BrowserTestUtils/content/content-utils.js
new file mode 100644
index 000000000..c1e56364c
--- /dev/null
+++ b/testing/mochitest/BrowserTestUtils/content/content-utils.js
@@ -0,0 +1,16 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+addEventListener("load", function(event) {
+  let subframe = event.target != content.document;
+  sendAsyncMessage("browser-test-utils:loadEvent",
+    {subframe: subframe, url: event.target.documentURI});
+}, true);
+
diff --git a/testing/mochitest/BrowserTestUtils/moz.build b/testing/mochitest/BrowserTestUtils/moz.build
new file mode 100644
index 000000000..25ef72d55
--- /dev/null
+++ b/testing/mochitest/BrowserTestUtils/moz.build
@@ -0,0 +1,11 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+TESTING_JS_MODULES += [
+    'BrowserTestUtils.jsm',
+    'ContentTask.jsm',
+    'ContentTaskUtils.jsm',
+]