Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");

XPCOMUtils.defineLazyModuleGetter(this, "Promise",
  "resource://gre/modules/Promise.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
  "resource://gre/modules/PlacesUtils.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "PlacesTestUtils",
  "resource://testing-common/PlacesTestUtils.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "TabCrashHandler",
  "resource:///modules/ContentCrashHandlers.jsm");

/**
 * Wait for a <notification> to be closed then call the specified callback.
 */
function waitForNotificationClose(notification, cb) {
  let parent = notification.parentNode;

  let observer = new MutationObserver(function onMutatations(mutations) {
    for (let mutation of mutations) {
      for (let i = 0; i < mutation.removedNodes.length; i++) {
        let node = mutation.removedNodes.item(i);
        if (node != notification) {
          continue;
        }
        observer.disconnect();
        cb();
      }
    }
  });
  observer.observe(parent, {childList: true});
}

function closeAllNotifications() {
  let notificationBox = document.getElementById("global-notificationbox");

  if (!notificationBox || !notificationBox.currentNotification) {
    return Promise.resolve();
  }

  return new Promise(resolve => {
    for (let notification of notificationBox.allNotifications) {
      waitForNotificationClose(notification, function() {
        if (notificationBox.allNotifications.length === 0) {
          resolve();
        }
      });
      notification.close();
    }

  });
}

function whenDelayedStartupFinished(aWindow, aCallback) {
  Services.obs.addObserver(function observer(aSubject, aTopic) {
    if (aWindow == aSubject) {
      Services.obs.removeObserver(observer, aTopic);
      executeSoon(aCallback);
    }
  }, "browser-delayed-startup-finished");
}

function updateTabContextMenu(tab, onOpened) {
  let menu = document.getElementById("tabContextMenu");
  if (!tab)
    tab = gBrowser.selectedTab;
  var evt = new Event("");
  tab.dispatchEvent(evt);
  menu.openPopup(tab, "end_after", 0, 0, true, false, evt);
  is(TabContextMenu.contextTab, tab, "TabContextMenu context is the expected tab");
  const onFinished = () => menu.hidePopup();
  if (onOpened) {
    return (async function() {
      await onOpened();
      onFinished();
    })();
  }
  onFinished();
  return Promise.resolve();
}

function openToolbarCustomizationUI(aCallback, aBrowserWin) {
  if (!aBrowserWin)
    aBrowserWin = window;

  aBrowserWin.gCustomizeMode.enter();

  aBrowserWin.gNavToolbox.addEventListener("customizationready", function() {
    executeSoon(function() {
      aCallback(aBrowserWin)
    });
  }, {once: true});
}

function closeToolbarCustomizationUI(aCallback, aBrowserWin) {
  aBrowserWin.gNavToolbox.addEventListener("aftercustomization", function() {
    executeSoon(aCallback);
  }, {once: true});

  aBrowserWin.gCustomizeMode.exit();
}

function waitForCondition(condition, nextTest, errorMsg, retryTimes) {
  retryTimes = typeof retryTimes !== "undefined" ? retryTimes : 30;
  var tries = 0;
  var interval = setInterval(function() {
    if (tries >= retryTimes) {
      ok(false, errorMsg);
      moveOn();
    }
    var conditionPassed;
    try {
      conditionPassed = condition();
    } catch (e) {
      ok(false, e + "\n" + e.stack);
      conditionPassed = false;
    }
    if (conditionPassed) {
      moveOn();
    }
    tries++;
  }, 100);
  var moveOn = function() { clearInterval(interval); nextTest(); };
}

function promiseWaitForCondition(aConditionFn) {
  return new Promise(resolve => {
    waitForCondition(aConditionFn, resolve, "Condition didn't pass.");
  });
}

function promiseWaitForEvent(object, eventName, capturing = false, chrome = false) {
  return new Promise((resolve) => {
    function listener(event) {
      info("Saw " + eventName);
      object.removeEventListener(eventName, listener, capturing, chrome);
      resolve(event);
    }

    info("Waiting for " + eventName);
    object.addEventListener(eventName, listener, capturing, chrome);
  });
}

/**
 * Allows setting focus on a window, and waiting for that window to achieve
 * focus.
 *
 * @param aWindow
 *        The window to focus and wait for.
 *
 * @return {Promise}
 * @resolves When the window is focused.
 * @rejects Never.
 */
function promiseWaitForFocus(aWindow) {
  return new Promise((resolve) => {
    waitForFocus(resolve, aWindow);
  });
}

function getTestPlugin(aName) {
  var pluginName = aName || "Test Plug-in";
  var ph = Cc["@mozilla.org/plugin/host;1"].getService(Ci.nsIPluginHost);
  var tags = ph.getPluginTags();

  // Find the test plugin
  for (var i = 0; i < tags.length; i++) {
    if (tags[i].name == pluginName)
      return tags[i];
  }
  ok(false, "Unable to find plugin");
  return null;
}

// call this to set the test plugin(s) initially expected enabled state.
// it will automatically be reset to it's previous value after the test
// ends
function setTestPluginEnabledState(newEnabledState, pluginName) {
  var plugin = getTestPlugin(pluginName);
  var oldEnabledState = plugin.enabledState;
  plugin.enabledState = newEnabledState;
  SimpleTest.registerCleanupFunction(function() {
    getTestPlugin(pluginName).enabledState = oldEnabledState;
  });
}

function pushPrefs(...aPrefs) {
  return new Promise(resolve => {
    SpecialPowers.pushPrefEnv({"set": aPrefs}, resolve);
  });
}

function updateBlocklist(aCallback) {
  var blocklistNotifier = Cc["@mozilla.org/extensions/blocklist;1"]
                          .getService(Ci.nsITimerCallback);
  var observer = function() {
    Services.obs.removeObserver(observer, "blocklist-updated");
    SimpleTest.executeSoon(aCallback);
  };
  Services.obs.addObserver(observer, "blocklist-updated");
  blocklistNotifier.notify(null);
}

var _originalTestBlocklistURL = null;
function setAndUpdateBlocklist(aURL, aCallback) {
  if (!_originalTestBlocklistURL)
    _originalTestBlocklistURL = Services.prefs.getCharPref("extensions.blocklist.url");
  Services.prefs.setCharPref("extensions.blocklist.url", aURL);
  updateBlocklist(aCallback);
}

function resetBlocklist() {
  Services.prefs.setCharPref("extensions.blocklist.url", _originalTestBlocklistURL);
}

function whenNewWindowLoaded(aOptions, aCallback) {
  let win = OpenBrowserWindow(aOptions);
  win.addEventListener("load", function() {
    aCallback(win);
  }, {once: true});
}

function promiseWindowWillBeClosed(win) {
  return new Promise((resolve, reject) => {
    Services.obs.addObserver(function observe(subject, topic) {
      if (subject == win) {
        Services.obs.removeObserver(observe, topic);
        resolve();
      }
    }, "domwindowclosed");
  });
}

function promiseWindowClosed(win) {
  let promise = promiseWindowWillBeClosed(win);
  win.close();
  return promise;
}

function promiseOpenAndLoadWindow(aOptions, aWaitForDelayedStartup = false) {
  return new Promise(resolve => {
    let win = OpenBrowserWindow(aOptions);
    if (aWaitForDelayedStartup) {
      Services.obs.addObserver(function onDS(aSubject, aTopic, aData) {
        if (aSubject != win) {
          return;
        }
        Services.obs.removeObserver(onDS, "browser-delayed-startup-finished");
        resolve(win);
      }, "browser-delayed-startup-finished");

    } else {
      win.addEventListener("load", function() {
        resolve(win);
      }, {once: true});
    }
  });
}

/**
 * Waits for all pending async statements on the default connection, before
 * proceeding with aCallback.
 *
 * @param aCallback
 *        Function to be called when done.
 * @param aScope
 *        Scope for the callback.
 * @param aArguments
 *        Arguments array for the callback.
 *
 * @note The result is achieved by asynchronously executing a query requiring
 *       a write lock.  Since all statements on the same connection are
 *       serialized, the end of this write operation means that all writes are
 *       complete.  Note that WAL makes so that writers don't block readers, but
 *       this is a problem only across different connections.
 */
function waitForAsyncUpdates(aCallback, aScope, aArguments) {
  let scope = aScope || this;
  let args = aArguments || [];
  let db = PlacesUtils.history.QueryInterface(Ci.nsPIPlacesDatabase)
                              .DBConnection;
  let begin = db.createAsyncStatement("BEGIN EXCLUSIVE");
  begin.executeAsync();
  begin.finalize();

  let commit = db.createAsyncStatement("COMMIT");
  commit.executeAsync({
    handleResult() {},
    handleError() {},
    handleCompletion(aReason) {
      aCallback.apply(scope, args);
    }
  });
  commit.finalize();
}

/**
 * Asynchronously check a url is visited.

 * @param aURI The URI.
 * @param aExpectedValue The expected value.
 * @return {Promise}
 * @resolves When the check has been added successfully.
 * @rejects JavaScript exception.
 */
function promiseIsURIVisited(aURI, aExpectedValue) {
  return new Promise(resolve => {
    PlacesUtils.asyncHistory.isURIVisited(aURI, function(unused, aIsVisited) {
      resolve(aIsVisited);
    });

  });
}

function whenNewTabLoaded(aWindow, aCallback) {
  aWindow.BrowserOpenTab();

  let browser = aWindow.gBrowser.selectedBrowser;
  if (browser.contentDocument.readyState === "complete") {
    aCallback();
    return;
  }

  whenTabLoaded(aWindow.gBrowser.selectedTab, aCallback);
}

function whenTabLoaded(aTab, aCallback) {
  promiseTabLoadEvent(aTab).then(aCallback);
}

function promiseTabLoaded(aTab) {
  return new Promise(resolve => {
    whenTabLoaded(aTab, resolve);
  });
}

/**
 * Ensures that the specified URIs are either cleared or not.
 *
 * @param aURIs
 *        Array of page URIs
 * @param aShouldBeCleared
 *        True if each visit to the URI should be cleared, false otherwise
 */
function promiseHistoryClearedState(aURIs, aShouldBeCleared) {
  return new Promise(resolve => {
    let callbackCount = 0;
    let niceStr = aShouldBeCleared ? "no longer" : "still";
    function callbackDone() {
      if (++callbackCount == aURIs.length)
        resolve();
    }
    aURIs.forEach(function(aURI) {
      PlacesUtils.asyncHistory.isURIVisited(aURI, function(uri, isVisited) {
        is(isVisited, !aShouldBeCleared,
           "history visit " + uri.spec + " should " + niceStr + " exist");
        callbackDone();
      });
    });

  });
}

/**
 * Waits for the next top-level document load in the current browser.  The URI
 * of the document is compared against aExpectedURL.  The load is then stopped
 * before it actually starts.
 *
 * @param aExpectedURL
 *        The URL of the document that is expected to load.
 * @param aStopFromProgressListener
 *        Whether to cancel the load directly from the progress listener. Defaults to true.
 *        If you're using this method to avoid hitting the network, you want the default (true).
 *        However, the browser UI will behave differently for loads stopped directly from
 *        the progress listener (effectively in the middle of a call to loadURI) and so there
 *        are cases where you may want to avoid stopping the load directly from within the
 *        progress listener callback.
 * @return promise
 */
function waitForDocLoadAndStopIt(aExpectedURL, aBrowser = gBrowser.selectedBrowser, aStopFromProgressListener = true) {
  function content_script(contentStopFromProgressListener) {
    let { interfaces: Ci, utils: Cu } = Components;
    Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
    let wp = docShell.QueryInterface(Ci.nsIWebProgress);

    function stopContent(now, uri) {
      if (now) {
        /* Hammer time. */
        content.stop();

        /* Let the parent know we're done. */
        sendAsyncMessage("Test:WaitForDocLoadAndStopIt", { uri });
      } else {
        setTimeout(stopContent.bind(null, true, uri), 0);
      }
    }

    let progressListener = {
      onStateChange(webProgress, req, flags, status) {
        dump("waitForDocLoadAndStopIt: onStateChange " + flags.toString(16) + ": " + req.name + "\n");

        if (webProgress.isTopLevel &&
            flags & Ci.nsIWebProgressListener.STATE_START) {
          wp.removeProgressListener(progressListener);

          let chan = req.QueryInterface(Ci.nsIChannel);
          dump(`waitForDocLoadAndStopIt: Document start: ${chan.URI.spec}\n`);

          stopContent(contentStopFromProgressListener, chan.originalURI.spec);
        }
      },
      QueryInterface: XPCOMUtils.generateQI(["nsISupportsWeakReference"])
    };
    wp.addProgressListener(progressListener, wp.NOTIFY_STATE_WINDOW);

    /**
     * As |this| is undefined and we can't extend |docShell|, adding an unload
     * event handler is the easiest way to ensure the weakly referenced
     * progress listener is kept alive as long as necessary.
     */
    addEventListener("unload", function() {
      try {
        wp.removeProgressListener(progressListener);
      } catch (e) { /* Will most likely fail. */ }
    });
  }

  return new Promise((resolve, reject) => {
    function complete({ data }) {
      is(data.uri, aExpectedURL, "waitForDocLoadAndStopIt: The expected URL was loaded");
      mm.removeMessageListener("Test:WaitForDocLoadAndStopIt", complete);
      resolve();
    }

    let mm = aBrowser.messageManager;
    mm.loadFrameScript("data:,(" + content_script.toString() + ")(" + aStopFromProgressListener + ");", true);
    mm.addMessageListener("Test:WaitForDocLoadAndStopIt", complete);
    info("waitForDocLoadAndStopIt: Waiting for URL: " + aExpectedURL);
  });
}

/**
 * Waits for the next load to complete in any browser or the given browser.
 * If a <tabbrowser> is given it waits for a load in any of its browsers.
 *
 * @return promise
 */
function waitForDocLoadComplete(aBrowser = gBrowser) {
  return new Promise(resolve => {
    let listener = {
      onStateChange(webProgress, req, flags, status) {
        let docStop = Ci.nsIWebProgressListener.STATE_IS_NETWORK |
                      Ci.nsIWebProgressListener.STATE_STOP;
        info("Saw state " + flags.toString(16) + " and status " + status.toString(16));

        // When a load needs to be retargetted to a new process it is cancelled
        // with NS_BINDING_ABORTED so ignore that case
        if ((flags & docStop) == docStop && status != Cr.NS_BINDING_ABORTED) {
          aBrowser.removeProgressListener(this);
          waitForDocLoadComplete.listeners.delete(this);

          let chan = req.QueryInterface(Ci.nsIChannel);
          info("Browser loaded " + chan.originalURI.spec);
          resolve();
        }
      },
      QueryInterface: XPCOMUtils.generateQI([Ci.nsIWebProgressListener,
                                             Ci.nsISupportsWeakReference])
    };
    aBrowser.addProgressListener(listener);
    waitForDocLoadComplete.listeners.add(listener);
    info("Waiting for browser load");
  });
}

// Keep a set of progress listeners for waitForDocLoadComplete() to make sure
// they're not GC'ed before we saw the page load.
waitForDocLoadComplete.listeners = new Set();
registerCleanupFunction(() => waitForDocLoadComplete.listeners.clear());

var FullZoomHelper = {

  selectTabAndWaitForLocationChange: function selectTabAndWaitForLocationChange(tab) {
    if (!tab)
      throw new Error("tab must be given.");
    if (gBrowser.selectedTab == tab)
      return Promise.resolve();

    return Promise.all([BrowserTestUtils.switchTab(gBrowser, tab),
                        this.waitForLocationChange()]);
  },

  removeTabAndWaitForLocationChange: function removeTabAndWaitForLocationChange(tab) {
    tab = tab || gBrowser.selectedTab;
    let selected = gBrowser.selectedTab == tab;
    gBrowser.removeTab(tab);
    if (selected)
      return this.waitForLocationChange();
    return Promise.resolve();
  },

  waitForLocationChange: function waitForLocationChange() {
    return new Promise(resolve => {
      Services.obs.addObserver(function obs(subj, topic, data) {
        Services.obs.removeObserver(obs, topic);
        resolve();
      }, "browser-fullZoom:location-change");
    });
  },

  load: function load(tab, url) {
    return new Promise(resolve => {
      let didLoad = false;
      let didZoom = false;

      promiseTabLoadEvent(tab).then(event => {
        didLoad = true;
        if (didZoom)
          resolve();
      }, true);

      this.waitForLocationChange().then(function() {
        didZoom = true;
        if (didLoad)
          resolve();
      });

      tab.linkedBrowser.loadURI(url);
    });
  },

  zoomTest: function zoomTest(tab, val, msg) {
    is(ZoomManager.getZoomForBrowser(tab.linkedBrowser), val, msg);
  },

  enlarge: function enlarge() {
    return new Promise(resolve => FullZoom.enlarge(resolve));
  },

  reduce: function reduce() {
    return new Promise(resolve => FullZoom.reduce(resolve));
  },

  reset: function reset() {
    return FullZoom.reset();
  },

  BACK: 0,
  FORWARD: 1,
  navigate: function navigate(direction) {
    return new Promise(resolve => {
      let didPs = false;
      let didZoom = false;

      gBrowser.addEventListener("pageshow", function(event) {
        didPs = true;
        if (didZoom)
          resolve();
      }, {capture: true, once: true});

      if (direction == this.BACK)
        gBrowser.goBack();
      else if (direction == this.FORWARD)
        gBrowser.goForward();

      this.waitForLocationChange().then(function() {
        didZoom = true;
        if (didPs)
          resolve();
      });
    });
  },

  failAndContinue: function failAndContinue(func) {
    return function(err) {
      ok(false, err);
      func();
    };
  },
};

/**
 * Waits for a load (or custom) event to finish in a given tab. If provided
 * load an uri into the tab.
 *
 * @param tab
 *        The tab to load into.
 * @param [optional] url
 *        The url to load, or the current url.
 * @return {Promise} resolved when the event is handled.
 * @resolves to the received event
 * @rejects if a valid load event is not received within a meaningful interval
 */
function promiseTabLoadEvent(tab, url) {
  info("Wait tab event: load");

  function handle(loadedUrl) {
    if (loadedUrl === "about:blank" || (url && loadedUrl !== url)) {
      info(`Skipping spurious load event for ${loadedUrl}`);
      return false;
    }

    info("Tab event received: load");
    return true;
  }

  let loaded = BrowserTestUtils.browserLoaded(tab.linkedBrowser, false, handle);

  if (url)
    BrowserTestUtils.loadURI(tab.linkedBrowser, url);

  return loaded;
}

/**
 * Returns a Promise that resolves once a new tab has been opened in
 * a xul:tabbrowser.
 *
 * @param aTabBrowser
 *        The xul:tabbrowser to monitor for a new tab.
 * @return {Promise}
 *        Resolved when the new tab has been opened.
 * @resolves to the TabOpen event that was fired.
 * @rejects Never.
 */
function waitForNewTabEvent(aTabBrowser) {
  return promiseWaitForEvent(aTabBrowser.tabContainer, "TabOpen");
}

function is_hidden(element) {
  var style = element.ownerGlobal.getComputedStyle(element);
  if (style.display == "none")
    return true;
  if (style.visibility != "visible")
    return true;
  if (style.display == "-moz-popup")
    return ["hiding", "closed"].indexOf(element.state) != -1;

  // Hiding a parent element will hide all its children
  if (element.parentNode != element.ownerDocument)
    return is_hidden(element.parentNode);

  return false;
}

function is_visible(element) {
  var style = element.ownerGlobal.getComputedStyle(element);
  if (style.display == "none")
    return false;
  if (style.visibility != "visible")
    return false;
  if (style.display == "-moz-popup" && element.state != "open")
    return false;

  // Hiding a parent element will hide all its children
  if (element.parentNode != element.ownerDocument)
    return is_visible(element.parentNode);

  return true;
}

function is_element_visible(element, msg) {
  isnot(element, null, "Element should not be null, when checking visibility");
  ok(is_visible(element), msg || "Element should be visible");
}

function is_element_hidden(element, msg) {
  isnot(element, null, "Element should not be null, when checking visibility");
  ok(is_hidden(element), msg || "Element should be hidden");
}

function promisePopupEvent(popup, eventSuffix) {
  let endState = {shown: "open", hidden: "closed"}[eventSuffix];

  if (popup.state == endState)
    return Promise.resolve();

  let eventType = "popup" + eventSuffix;
  return new Promise(resolve => {
    popup.addEventListener(eventType, function(event) {
      resolve();
    }, {once: true});

  });
}

function promisePopupShown(popup) {
  return promisePopupEvent(popup, "shown");
}

function promisePopupHidden(popup) {
  return promisePopupEvent(popup, "hidden");
}

function promiseNotificationShown(notification) {
  let win = notification.browser.ownerGlobal;
  if (win.PopupNotifications.panel.state == "open") {
    return Promise.resolve();
  }
  let panelPromise = promisePopupShown(win.PopupNotifications.panel);
  notification.reshow();
  return panelPromise;
}

/**
 * Allows waiting for an observer notification once.
 *
 * @param aTopic
 *        Notification topic to observe.
 *
 * @return {Promise}
 * @resolves An object with subject and data properties from the observed
 *           notification.
 * @rejects Never.
 */
function promiseTopicObserved(aTopic) {
  return new Promise((resolve) => {
    Services.obs.addObserver(
      function PTO_observe(aSubject, aTopic2, aData) {
        Services.obs.removeObserver(PTO_observe, aTopic2);
        resolve({subject: aSubject, data: aData});
      }, aTopic);
  });
}

function promiseNewSearchEngine(basename) {
  return new Promise((resolve, reject) => {
    info("Waiting for engine to be added: " + basename);
    let url = getRootDirectory(gTestPath) + basename;
    Services.search.addEngine(url, null, "", false, {
      onSuccess(engine) {
        info("Search engine added: " + basename);
        registerCleanupFunction(() => Services.search.removeEngine(engine));
        resolve(engine);
      },
      onError(errCode) {
        Assert.ok(false, "addEngine failed with error code " + errCode);
        reject();
      },
    });
  });
}

/**
 * Resolves when a bookmark with the given uri is added.
 */
function promiseOnBookmarkItemAdded(aExpectedURI) {
  return new Promise((resolve, reject) => {
    let bookmarksObserver = {
      onItemAdded(aItemId, aFolderId, aIndex, aItemType, aURI) {
        info("Added a bookmark to " + aURI.spec);
        PlacesUtils.bookmarks.removeObserver(bookmarksObserver);
        if (aURI.equals(aExpectedURI)) {
          resolve();
        } else {
          reject(new Error("Added an unexpected bookmark"));
        }
      },
      onBeginUpdateBatch() {},
      onEndUpdateBatch() {},
      onItemRemoved() {},
      onItemChanged() {},
      onItemVisited() {},
      onItemMoved() {},
      QueryInterface: XPCOMUtils.generateQI([
        Ci.nsINavBookmarkObserver,
      ])
    };
    info("Waiting for a bookmark to be added");
    PlacesUtils.bookmarks.addObserver(bookmarksObserver);
  });
}

async function loadBadCertPage(url) {
  const EXCEPTION_DIALOG_URI = "chrome://pippki/content/exceptionDialog.xul";
  let exceptionDialogResolved = new Promise(function(resolve) {
    // When the certificate exception dialog has opened, click the button to add
    // an exception.
    let certExceptionDialogObserver = {
      observe(aSubject, aTopic, aData) {
        if (aTopic == "cert-exception-ui-ready") {
          Services.obs.removeObserver(this, "cert-exception-ui-ready");
          let certExceptionDialog = getCertExceptionDialog(EXCEPTION_DIALOG_URI);
          ok(certExceptionDialog, "found exception dialog");
          executeSoon(function() {
            certExceptionDialog.documentElement.getButton("extra1").click();
            resolve();
          });
        }
      }
    };

    Services.obs.addObserver(certExceptionDialogObserver,
                             "cert-exception-ui-ready");
  });

  let loaded = BrowserTestUtils.waitForErrorPage(gBrowser.selectedBrowser);
  await BrowserTestUtils.loadURI(gBrowser.selectedBrowser, url);
  await loaded;

  await ContentTask.spawn(gBrowser.selectedBrowser, null, async function() {
    content.document.getElementById("exceptionDialogButton").click();
  });
  await exceptionDialogResolved;
  await BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser);
}

// Utility function to get a handle on the certificate exception dialog.
// Modified from toolkit/components/passwordmgr/test/prompt_common.js
function getCertExceptionDialog(aLocation) {
  let enumerator = Services.wm.getXULWindowEnumerator(null);

  while (enumerator.hasMoreElements()) {
    let win = enumerator.getNext();
    let windowDocShell = win.QueryInterface(Ci.nsIXULWindow).docShell;

    let containedDocShells = windowDocShell.getDocShellEnumerator(
                                      Ci.nsIDocShellTreeItem.typeChrome,
                                      Ci.nsIDocShell.ENUMERATE_FORWARDS);
    while (containedDocShells.hasMoreElements()) {
      // Get the corresponding document for this docshell
      let childDocShell = containedDocShells.getNext();
      let childDoc = childDocShell.QueryInterface(Ci.nsIDocShell)
                                  .contentViewer
                                  .DOMDocument;

      if (childDoc.location.href == aLocation) {
        return childDoc;
      }
    }
  }
  return undefined;
}