The Tor Browser: dom/browser-element/BrowserElementChildPreload.js@6474c204b198 (annotated)

dom/browser-element/BrowserElementChildPreload.js@6474c204b198 (annotated)

dom/browser-element/BrowserElementChildPreload.js

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* 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";
 dump("######################## BrowserElementChildPreload.js loaded\n");
 var BrowserElementIsReady = false;
 let { classes: Cc, interfaces: Ci, results: Cr, utils: Cu }  = Components;
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/BrowserElementPromptService.jsm");
 // Event whitelisted for bubbling.
 let whitelistedEvents = [
   Ci.nsIDOMKeyEvent.DOM_VK_ESCAPE,   // Back button.
   Ci.nsIDOMKeyEvent.DOM_VK_SLEEP,    // Power button.
   Ci.nsIDOMKeyEvent.DOM_VK_CONTEXT_MENU,
   Ci.nsIDOMKeyEvent.DOM_VK_F5,       // Search button.
   Ci.nsIDOMKeyEvent.DOM_VK_PAGE_UP,  // Volume up.
   Ci.nsIDOMKeyEvent.DOM_VK_PAGE_DOWN // Volume down.
 ];
 function debug(msg) {
   //dump("BrowserElementChildPreload - " + msg + "\n");
 }
 function sendAsyncMsg(msg, data) {
   // Ensure that we don't send any messages before BrowserElementChild.js
   // finishes loading.
   if (!BrowserElementIsReady)
     return;
   if (!data) {
     data = { };
   }
   data.msg_name = msg;
   sendAsyncMessage('browser-element-api:call', data);
 }
 function sendSyncMsg(msg, data) {
   // Ensure that we don't send any messages before BrowserElementChild.js
   // finishes loading.
   if (!BrowserElementIsReady)
     return;
   if (!data) {
     data = { };
   }
   data.msg_name = msg;
   return sendSyncMessage('browser-element-api:call', data);
 }
 let CERTIFICATE_ERROR_PAGE_PREF = 'security.alternate_certificate_error_page';
 let NS_ERROR_MODULE_BASE_OFFSET = 0x45;
 let NS_ERROR_MODULE_SECURITY= 21;
 function NS_ERROR_GET_MODULE(err) {
   return ((((err) >> 16) - NS_ERROR_MODULE_BASE_OFFSET) & 0x1fff);
 }
 function NS_ERROR_GET_CODE(err) {
   return ((err) & 0xffff);
 }
 let SEC_ERROR_BASE = Ci.nsINSSErrorsService.NSS_SEC_ERROR_BASE;
 let SEC_ERROR_UNKNOWN_ISSUER = (SEC_ERROR_BASE + 13);
 let SEC_ERROR_CA_CERT_INVALID =   (SEC_ERROR_BASE + 36);
 let SEC_ERROR_UNTRUSTED_ISSUER = (SEC_ERROR_BASE + 20);
 let SEC_ERROR_EXPIRED_ISSUER_CERTIFICATE = (SEC_ERROR_BASE + 30);
 let SEC_ERROR_UNTRUSTED_CERT = (SEC_ERROR_BASE + 21);
 let SEC_ERROR_EXPIRED_CERTIFICATE = (SEC_ERROR_BASE + 11);
 let SEC_ERROR_CERT_SIGNATURE_ALGORITHM_DISABLED = (SEC_ERROR_BASE + 176);
 let SSL_ERROR_BASE = Ci.nsINSSErrorsService.NSS_SSL_ERROR_BASE;
 let SSL_ERROR_BAD_CERT_DOMAIN = (SSL_ERROR_BASE + 12);
 function getErrorClass(errorCode) {
   let NSPRCode = -1 * NS_ERROR_GET_CODE(errorCode);
   switch (NSPRCode) {
     case SEC_ERROR_UNKNOWN_ISSUER:
     case SEC_ERROR_UNTRUSTED_ISSUER:
     case SEC_ERROR_EXPIRED_ISSUER_CERTIFICATE:
     case SEC_ERROR_UNTRUSTED_CERT:
     case SSL_ERROR_BAD_CERT_DOMAIN:
     case SEC_ERROR_EXPIRED_CERTIFICATE:
     case SEC_ERROR_CERT_SIGNATURE_ALGORITHM_DISABLED:
     case SEC_ERROR_CA_CERT_INVALID:
       return Ci.nsINSSErrorsService.ERROR_CLASS_BAD_CERT;
     default:
       return Ci.nsINSSErrorsService.ERROR_CLASS_SSL_PROTOCOL;
   }
   return null;
 }
 const OBSERVED_EVENTS = [
   'fullscreen-origin-change',
   'ask-parent-to-exit-fullscreen',
   'ask-parent-to-rollback-fullscreen',
   'xpcom-shutdown',
   'activity-done'
 ];
 /**
  * The BrowserElementChild implements one half of <iframe mozbrowser>.
  * (The other half is, unsurprisingly, BrowserElementParent.)
  *
  * This script is injected into an <iframe mozbrowser> via
  * nsIMessageManager::LoadFrameScript().
  *
  * Our job here is to listen for events within this frame and bubble them up to
  * the parent process.
  */
 var global = this;
 function BrowserElementChild() {
   // Maps outer window id --> weak ref to window.  Used by modal dialog code.
   this._windowIDDict = {};
   // _forcedVisible corresponds to the visibility state our owner has set on us
   // (via iframe.setVisible).  ownerVisible corresponds to whether the docShell
   // whose window owns this element is visible.
   //
   // Our docShell is visible iff _forcedVisible and _ownerVisible are both
   // true.
   this._forcedVisible = true;
   this._ownerVisible = true;
   this._nextPaintHandler = null;
   this._isContentWindowCreated = false;
   this._pendingSetInputMethodActive = [];
   this._init();
 };
 BrowserElementChild.prototype = {
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver,
                                          Ci.nsISupportsWeakReference]),
   _init: function() {
     debug("Starting up.");
     BrowserElementPromptService.mapWindowToBrowserElementChild(content, this);
     docShell.QueryInterface(Ci.nsIWebProgress)
             .addProgressListener(this._progressListener,
                                  Ci.nsIWebProgress.NOTIFY_LOCATION |
                                  Ci.nsIWebProgress.NOTIFY_SECURITY |
                                  Ci.nsIWebProgress.NOTIFY_STATE_WINDOW);
     docShell.QueryInterface(Ci.nsIWebNavigation)
             .sessionHistory = Cc["@mozilla.org/browser/shistory;1"]
                                 .createInstance(Ci.nsISHistory);
     // This is necessary to get security web progress notifications.
     var securityUI = Cc['@mozilla.org/secure_browser_ui;1']
                        .createInstance(Ci.nsISecureBrowserUI);
     securityUI.init(content);
     // A cache of the menuitem dom objects keyed by the id we generate
     // and pass to the embedder
     this._ctxHandlers = {};
     // Counter of contextmenu events fired
     this._ctxCounter = 0;
     this._shuttingDown = false;
     addEventListener('DOMTitleChanged',
                      this._titleChangedHandler.bind(this),
                      /* useCapture = */ true,
                      /* wantsUntrusted = */ false);
     addEventListener('DOMLinkAdded',
                      this._linkAddedHandler.bind(this),
                      /* useCapture = */ true,
                      /* wantsUntrusted = */ false);
     addEventListener('DOMMetaAdded',
                      this._metaAddedHandler.bind(this),
                      /* useCapture = */ true,
                      /* wantsUntrusted = */ false);
     // This listens to unload events from our message manager, but /not/ from
     // the |content| window.  That's because the window's unload event doesn't
     // bubble, and we're not using a capturing listener.  If we'd used
     // useCapture == true, we /would/ hear unload events from the window, which
     // is not what we want!
     addEventListener('unload',
                      this._unloadHandler.bind(this),
                      /* useCapture = */ false,
                      /* wantsUntrusted = */ false);
     // Registers a MozAfterPaint handler for the very first paint.
     this._addMozAfterPaintHandler(function () {
       sendAsyncMsg('firstpaint');
     });
     let self = this;
     let mmCalls = {
       "purge-history": this._recvPurgeHistory,
       "get-screenshot": this._recvGetScreenshot,
       "set-visible": this._recvSetVisible,
       "get-visible": this._recvVisible,
       "send-mouse-event": this._recvSendMouseEvent,
       "send-touch-event": this._recvSendTouchEvent,
       "get-can-go-back": this._recvCanGoBack,
       "get-can-go-forward": this._recvCanGoForward,
       "go-back": this._recvGoBack,
       "go-forward": this._recvGoForward,
       "reload": this._recvReload,
       "stop": this._recvStop,
       "unblock-modal-prompt": this._recvStopWaiting,
       "fire-ctx-callback": this._recvFireCtxCallback,
       "owner-visibility-change": this._recvOwnerVisibilityChange,
       "exit-fullscreen": this._recvExitFullscreen.bind(this),
       "activate-next-paint-listener": this._activateNextPaintListener.bind(this),
       "set-input-method-active": this._recvSetInputMethodActive.bind(this),
       "deactivate-next-paint-listener": this._deactivateNextPaintListener.bind(this)
     }
     addMessageListener("browser-element-api:call", function(aMessage) {
       if (aMessage.data.msg_name in mmCalls) {
         return mmCalls[aMessage.data.msg_name].apply(self, arguments);
       }
     });
     let els = Cc["@mozilla.org/eventlistenerservice;1"]
                 .getService(Ci.nsIEventListenerService);
     // We are using the system group for those events so if something in the
     // content called .stopPropagation() this will still be called.
     els.addSystemEventListener(global, 'keydown',
                                this._keyEventHandler.bind(this),
                                /* useCapture = */ true);
     els.addSystemEventListener(global, 'keypress',
                                this._keyEventHandler.bind(this),
                                /* useCapture = */ true);
     els.addSystemEventListener(global, 'keyup',
                                this._keyEventHandler.bind(this),
                                /* useCapture = */ true);
     els.addSystemEventListener(global, 'DOMWindowClose',
                                this._windowCloseHandler.bind(this),
                                /* useCapture = */ false);
     els.addSystemEventListener(global, 'DOMWindowCreated',
                                this._windowCreatedHandler.bind(this),
                                /* useCapture = */ true);
     els.addSystemEventListener(global, 'DOMWindowResize',
                                this._windowResizeHandler.bind(this),
                                /* useCapture = */ false);
     els.addSystemEventListener(global, 'contextmenu',
                                this._contextmenuHandler.bind(this),
                                /* useCapture = */ false);
     els.addSystemEventListener(global, 'scroll',
                                this._scrollEventHandler.bind(this),
                                /* useCapture = */ false);
     OBSERVED_EVENTS.forEach((aTopic) => {
       Services.obs.addObserver(this, aTopic, false);
     });
   },
   observe: function(subject, topic, data) {
     // Ignore notifications not about our document.  (Note that |content| /can/
     // be null; see bug 874900.)
     if (topic !== 'activity-done' && (!content || subject != content.document))
       return;
     if (topic == 'activity-done' && docShell !== subject)
       return;
     switch (topic) {
       case 'fullscreen-origin-change':
         sendAsyncMsg('fullscreen-origin-change', { _payload_: data });
         break;
       case 'ask-parent-to-exit-fullscreen':
         sendAsyncMsg('exit-fullscreen');
         break;
       case 'ask-parent-to-rollback-fullscreen':
         sendAsyncMsg('rollback-fullscreen');
         break;
       case 'activity-done':
         sendAsyncMsg('activitydone', { success: (data == 'activity-success') });
         break;
       case 'xpcom-shutdown':
         this._shuttingDown = true;
         break;
     }
   },
   /**
    * Called when our TabChildGlobal starts to die.  This is not called when the
    * page inside |content| unloads.
    */
   _unloadHandler: function() {
     this._shuttingDown = true;
     OBSERVED_EVENTS.forEach((aTopic) => {
       Services.obs.removeObserver(this, aTopic);
     });
   },
   _tryGetInnerWindowID: function(win) {
     let utils = win.QueryInterface(Ci.nsIInterfaceRequestor)
                    .getInterface(Ci.nsIDOMWindowUtils);
     try {
       return utils.currentInnerWindowID;
     }
     catch(e) {
       return null;
     }
   },
   /**
    * Show a modal prompt.  Called by BrowserElementPromptService.
    */
   showModalPrompt: function(win, args) {
     let utils = win.QueryInterface(Ci.nsIInterfaceRequestor)
                    .getInterface(Ci.nsIDOMWindowUtils);
     args.windowID = { outer: utils.outerWindowID,
                       inner: this._tryGetInnerWindowID(win) };
     sendAsyncMsg('showmodalprompt', args);
     let returnValue = this._waitForResult(win);
     Services.obs.notifyObservers(null, 'BEC:ShownModalPrompt', null);
     if (args.promptType == 'prompt' ||
         args.promptType == 'confirm' ||
         args.promptType == 'custom-prompt') {
       return returnValue;
     }
   },
   /**
    * Spin in a nested event loop until we receive a unblock-modal-prompt message for
    * this window.
    */
   _waitForResult: function(win) {
     debug("_waitForResult(" + win + ")");
     let utils = win.QueryInterface(Ci.nsIInterfaceRequestor)
                    .getInterface(Ci.nsIDOMWindowUtils);
     let outerWindowID = utils.outerWindowID;
     let innerWindowID = this._tryGetInnerWindowID(win);
     if (innerWindowID === null) {
       // I have no idea what waiting for a result means when there's no inner
       // window, so let's just bail.
       debug("_waitForResult: No inner window. Bailing.");
       return;
     }
     this._windowIDDict[outerWindowID] = Cu.getWeakReference(win);
     debug("Entering modal state (outerWindowID=" + outerWindowID + ", " +
                                 "innerWindowID=" + innerWindowID + ")");
     utils.enterModalState();
     // We'll decrement win.modalDepth when we receive a unblock-modal-prompt message
     // for the window.
     if (!win.modalDepth) {
       win.modalDepth = 0;
     }
     win.modalDepth++;
     let origModalDepth = win.modalDepth;
     let thread = Services.tm.currentThread;
     debug("Nested event loop - begin");
     while (win.modalDepth == origModalDepth && !this._shuttingDown) {
       // Bail out of the loop if the inner window changed; that means the
       // window navigated.  Bail out when we're shutting down because otherwise
       // we'll leak our window.
       if (this._tryGetInnerWindowID(win) !== innerWindowID) {
         debug("_waitForResult: Inner window ID changed " +
               "while in nested event loop.");
         break;
       }
       thread.processNextEvent(/* mayWait = */ true);
     }
     debug("Nested event loop - finish");
     // If we exited the loop because the inner window changed, then bail on the
     // modal prompt.
     if (innerWindowID !== this._tryGetInnerWindowID(win)) {
       throw Components.Exception("Modal state aborted by navigation",
                                  Cr.NS_ERROR_NOT_AVAILABLE);
     }
     let returnValue = win.modalReturnValue;
     delete win.modalReturnValue;
     if (!this._shuttingDown) {
       utils.leaveModalState();
     }
     debug("Leaving modal state (outerID=" + outerWindowID + ", " +
                                "innerID=" + innerWindowID + ")");
     return returnValue;
   },
   _recvStopWaiting: function(msg) {
     let outerID = msg.json.windowID.outer;
     let innerID = msg.json.windowID.inner;
     let returnValue = msg.json.returnValue;
     debug("recvStopWaiting(outer=" + outerID + ", inner=" + innerID +
           ", returnValue=" + returnValue + ")");
     if (!this._windowIDDict[outerID]) {
       debug("recvStopWaiting: No record of outer window ID " + outerID);
       return;
     }
     let win = this._windowIDDict[outerID].get();
     delete this._windowIDDict[outerID];
     if (!win) {
       debug("recvStopWaiting, but window is gone\n");
       return;
     }
     if (innerID !== this._tryGetInnerWindowID(win)) {
       debug("recvStopWaiting, but inner ID has changed\n");
       return;
     }
     debug("recvStopWaiting " + win);
     win.modalReturnValue = returnValue;
     win.modalDepth--;
   },
   _recvExitFullscreen: function() {
     var utils = content.document.defaultView
                        .QueryInterface(Ci.nsIInterfaceRequestor)
                        .getInterface(Ci.nsIDOMWindowUtils);
     utils.exitFullscreen();
   },
   _titleChangedHandler: function(e) {
     debug("Got titlechanged: (" + e.target.title + ")");
     var win = e.target.defaultView;
     // Ignore titlechanges which don't come from the top-level
     // <iframe mozbrowser> window.
     if (win == content) {
       sendAsyncMsg('titlechange', { _payload_: e.target.title });
     }
     else {
       debug("Not top level!");
     }
   },
   _iconChangedHandler: function(e) {
     debug('Got iconchanged: (' + e.target.href + ')');
     let icon = { href: e.target.href };
     if (e.target.getAttribute('sizes')) {
       icon.sizes = e.target.getAttribute('sizes');
     }
     sendAsyncMsg('iconchange', icon);
   },
   _openSearchHandler: function(e) {
     debug('Got opensearch: (' + e.target.href + ')');
     if (e.target.type !== "application/opensearchdescription+xml") {
       return;
     }
     sendAsyncMsg('opensearch', { title: e.target.title,
                                  href: e.target.href });
   },
   _manifestChangedHandler: function(e) {
     debug('Got manifestchanged: (' + e.target.href + ')');
     let manifest = { href: e.target.href };
     sendAsyncMsg('manifestchange', manifest);
   },
   // Processes the "rel" field in <link> tags and forward to specific handlers.
   _linkAddedHandler: function(e) {
     let win = e.target.ownerDocument.defaultView;
     // Ignore links which don't come from the top-level
     // <iframe mozbrowser> window.
     if (win != content) {
       debug('Not top level!');
       return;
     }
     let handlers = {
       'icon': this._iconChangedHandler,
       'search': this._openSearchHandler,
       'manifest': this._manifestChangedHandler
     };
     debug('Got linkAdded: (' + e.target.href + ') ' + e.target.rel);
     e.target.rel.split(' ').forEach(function(x) {
       let token = x.toLowerCase();
       if (handlers[token]) {
         handlers[token](e);
       }
     }, this);
   },
   _metaAddedHandler: function(e) {
     let win = e.target.ownerDocument.defaultView;
     // Ignore metas which don't come from the top-level
     // <iframe mozbrowser> window.
     if (win != content) {
       debug('Not top level!');
       return;
     }
     if (!e.target.name) {
       return;
     }
     debug('Got metaAdded: (' + e.target.name + ') ' + e.target.content);
     if (e.target.name == 'application-name') {
       let meta = { name: e.target.name,
                    content: e.target.content };
       let lang;
       let elm;
       for (elm = e.target;
            !lang && elm && elm.nodeType == e.target.ELEMENT_NODE;
            elm = elm.parentNode) {
         if (elm.hasAttribute('lang')) {
           lang = elm.getAttribute('lang');
           continue;
         }
         if (elm.hasAttributeNS('http://www.w3.org/XML/1998/namespace', 'lang')) {
           lang = elm.getAttributeNS('http://www.w3.org/XML/1998/namespace', 'lang');
           continue;
         }
       }
       // No lang has been detected.
       if (!lang && elm.nodeType == e.target.DOCUMENT_NODE) {
         lang = elm.contentLanguage;
       }
       if (lang) {
         meta.lang = lang;
       }
       sendAsyncMsg('metachange', meta);
     }
   },
   _addMozAfterPaintHandler: function(callback) {
     function onMozAfterPaint() {
       let uri = docShell.QueryInterface(Ci.nsIWebNavigation).currentURI;
       if (uri.spec != "about:blank") {
         debug("Got afterpaint event: " + uri.spec);
         removeEventListener('MozAfterPaint', onMozAfterPaint,
                             /* useCapture = */ true);
         callback();
       }
     }
     addEventListener('MozAfterPaint', onMozAfterPaint, /* useCapture = */ true);
     return onMozAfterPaint;
   },
   _removeMozAfterPaintHandler: function(listener) {
     removeEventListener('MozAfterPaint', listener,
                         /* useCapture = */ true);
   },
   _activateNextPaintListener: function(e) {
     if (!this._nextPaintHandler) {
       this._nextPaintHandler = this._addMozAfterPaintHandler(function () {
         this._nextPaintHandler = null;
         sendAsyncMsg('nextpaint');
       }.bind(this));
     }
   },
   _deactivateNextPaintListener: function(e) {
     if (this._nextPaintHandler) {
       this._removeMozAfterPaintHandler(this._nextPaintHandler);
       this._nextPaintHandler = null;
     }
   },
   _windowCloseHandler: function(e) {
     let win = e.target;
     if (win != content || e.defaultPrevented) {
       return;
     }
     debug("Closing window " + win);
     sendAsyncMsg('close');
     // Inform the window implementation that we handled this close ourselves.
     e.preventDefault();
   },
   _windowCreatedHandler: function(e) {
     let targetDocShell = e.target.defaultView
           .QueryInterface(Ci.nsIInterfaceRequestor)
           .getInterface(Ci.nsIWebNavigation);
     if (targetDocShell != docShell) {
       return;
     }
     let uri = docShell.QueryInterface(Ci.nsIWebNavigation).currentURI;
     debug("Window created: " + uri.spec);
     if (uri.spec != "about:blank") {
       this._addMozAfterPaintHandler(function () {
         sendAsyncMsg('documentfirstpaint');
       });
       this._isContentWindowCreated = true;
       // Handle pending SetInputMethodActive request.
       while (this._pendingSetInputMethodActive.length > 0) {
         this._recvSetInputMethodActive(this._pendingSetInputMethodActive.shift());
       }
     }
   },
   _windowResizeHandler: function(e) {
     let win = e.target;
     if (win != content || e.defaultPrevented) {
       return;
     }
     debug("resizing window " + win);
     sendAsyncMsg('resize', { width: e.detail.width, height: e.detail.height });
     // Inform the window implementation that we handled this resize ourselves.
     e.preventDefault();
   },
   _contextmenuHandler: function(e) {
     debug("Got contextmenu");
     if (e.defaultPrevented) {
       return;
     }
     this._ctxCounter++;
     this._ctxHandlers = {};
     var elem = e.target;
     var menuData = {systemTargets: [], contextmenu: null};
     var ctxMenuId = null;
     while (elem && elem.parentNode) {
       var ctxData = this._getSystemCtxMenuData(elem);
       if (ctxData) {
         menuData.systemTargets.push({
           nodeName: elem.nodeName,
           data: ctxData
         });
       }
       if (!ctxMenuId && 'hasAttribute' in elem && elem.hasAttribute('contextmenu')) {
         ctxMenuId = elem.getAttribute('contextmenu');
       }
       elem = elem.parentNode;
     }
     if (ctxMenuId) {
       var menu = e.target.ownerDocument.getElementById(ctxMenuId);
       if (menu) {
         menuData.contextmenu = this._buildMenuObj(menu, '');
       }
     }
     // The value returned by the contextmenu sync call is true iff the embedder
     // called preventDefault() on its contextmenu event.
     //
     // We call preventDefault() on our contextmenu event iff the embedder called
     // preventDefault() on /its/ contextmenu event.  This way, if the embedder
     // ignored the contextmenu event, TabChild will fire a click.
     if (sendSyncMsg('contextmenu', menuData)[0]) {
       e.preventDefault();
     } else {
       this._ctxHandlers = {};
     }
   },
   _getSystemCtxMenuData: function(elem) {
     if ((elem instanceof Ci.nsIDOMHTMLAnchorElement && elem.href) ||
         (elem instanceof Ci.nsIDOMHTMLAreaElement && elem.href)) {
       return {uri: elem.href};
     }
     if (elem instanceof Ci.nsIImageLoadingContent && elem.currentURI) {
       return {uri: elem.currentURI.spec};
     }
     if (elem instanceof Ci.nsIDOMHTMLImageElement) {
       return {uri: elem.src};
     }
     if (elem instanceof Ci.nsIDOMHTMLMediaElement) {
       let hasVideo = !(elem.readyState >= elem.HAVE_METADATA &&
                        (elem.videoWidth == 0 || elem.videoHeight == 0));
       return {uri: elem.currentSrc || elem.src, hasVideo: hasVideo};
     }
     return false;
   },
   _scrollEventHandler: function(e) {
     let win = e.target.defaultView;
     if (win != content) {
       return;
     }
     debug("scroll event " + win);
     sendAsyncMsg("scroll", { top: win.scrollY, left: win.scrollX });
   },
   _recvPurgeHistory: function(data) {
     debug("Received purgeHistory message: (" + data.json.id + ")");
     let history = docShell.QueryInterface(Ci.nsIWebNavigation).sessionHistory;
     try {
       if (history && history.count) {
         history.PurgeHistory(history.count);
       }
     } catch(e) {}
     sendAsyncMsg('got-purge-history', { id: data.json.id, successRv: true });
   },
   _recvGetScreenshot: function(data) {
     debug("Received getScreenshot message: (" + data.json.id + ")");
     let self = this;
     let maxWidth = data.json.args.width;
     let maxHeight = data.json.args.height;
     let mimeType = data.json.args.mimeType;
     let domRequestID = data.json.id;
     let takeScreenshotClosure = function() {
       self._takeScreenshot(maxWidth, maxHeight, mimeType, domRequestID);
     };
     let maxDelayMS = 2000;
     try {
       maxDelayMS = Services.prefs.getIntPref('dom.browserElement.maxScreenshotDelayMS');
     }
     catch(e) {}
     // Try to wait for the event loop to go idle before we take the screenshot,
     // but once we've waited maxDelayMS milliseconds, go ahead and take it
     // anyway.
     Cc['@mozilla.org/message-loop;1'].getService(Ci.nsIMessageLoop).postIdleTask(
       takeScreenshotClosure, maxDelayMS);
   },
   /**
    * Actually take a screenshot and foward the result up to our parent, given
    * the desired maxWidth and maxHeight (in CSS pixels), and given the
    * DOMRequest ID associated with the request from the parent.
    */
   _takeScreenshot: function(maxWidth, maxHeight, mimeType, domRequestID) {
     // You can think of the screenshotting algorithm as carrying out the
     // following steps:
     //
     // - Calculate maxWidth, maxHeight, and viewport's width and height in the
     //   dimension of device pixels by multiply the numbers with
     //   window.devicePixelRatio.
     //
     // - Let scaleWidth be the factor by which we'd need to downscale the
     //   viewport pixel width so it would fit within maxPixelWidth.
     //   (If the viewport's pixel width is less than maxPixelWidth, let
     //   scaleWidth be 1.) Compute scaleHeight the same way.
     //
     // - Scale the viewport by max(scaleWidth, scaleHeight).  Now either the
     //   viewport's width is no larger than maxWidth, the viewport's height is
     //   no larger than maxHeight, or both.
     //
     // - Crop the viewport so its width is no larger than maxWidth and its
     //   height is no larger than maxHeight.
     //
     // - Set mozOpaque to true and background color to solid white
     //   if we are taking a JPEG screenshot, keep transparent if otherwise.
     //
     // - Return a screenshot of the page's viewport scaled and cropped per
     //   above.
     debug("Taking a screenshot: maxWidth=" + maxWidth +
           ", maxHeight=" + maxHeight +
           ", mimeType=" + mimeType +
           ", domRequestID=" + domRequestID + ".");
     if (!content) {
       // If content is not loaded yet, bail out since even sendAsyncMessage
       // fails...
       debug("No content yet!");
       return;
     }
     let devicePixelRatio = content.devicePixelRatio;
     let maxPixelWidth = Math.round(maxWidth * devicePixelRatio);
     let maxPixelHeight = Math.round(maxHeight * devicePixelRatio);
     let contentPixelWidth = content.innerWidth * devicePixelRatio;
     let contentPixelHeight = content.innerHeight * devicePixelRatio;
     let scaleWidth = Math.min(1, maxPixelWidth / contentPixelWidth);
     let scaleHeight = Math.min(1, maxPixelHeight / contentPixelHeight);
     let scale = Math.max(scaleWidth, scaleHeight);
     let canvasWidth =
       Math.min(maxPixelWidth, Math.round(contentPixelWidth * scale));
     let canvasHeight =
       Math.min(maxPixelHeight, Math.round(contentPixelHeight * scale));
     let transparent = (mimeType !== 'image/jpeg');
     var canvas = content.document
       .createElementNS("http://www.w3.org/1999/xhtml", "canvas");
     if (!transparent)
       canvas.mozOpaque = true;
     canvas.width = canvasWidth;
     canvas.height = canvasHeight;
     let ctx = canvas.getContext("2d", { willReadFrequently: true });
     ctx.scale(scale * devicePixelRatio, scale * devicePixelRatio);
     let flags = ctx.DRAWWINDOW_DRAW_VIEW |
                 ctx.DRAWWINDOW_USE_WIDGET_LAYERS |
                 ctx.DRAWWINDOW_DO_NOT_FLUSH |
                 ctx.DRAWWINDOW_ASYNC_DECODE_IMAGES;
     ctx.drawWindow(content, 0, 0, content.innerWidth, content.innerHeight,
                    transparent ? "rgba(255,255,255,0)" : "rgb(255,255,255)",
                    flags);
     // Take a JPEG screenshot by default instead of PNG with alpha channel.
     // This requires us to unpremultiply the alpha channel, which
     // is expensive on ARM processors because they lack a hardware integer
     // division instruction.
     canvas.toBlob(function(blob) {
       sendAsyncMsg('got-screenshot', {
         id: domRequestID,
         successRv: blob
       });
     }, mimeType);
   },
   _recvFireCtxCallback: function(data) {
     debug("Received fireCtxCallback message: (" + data.json.menuitem + ")");
     // We silently ignore if the embedder uses an incorrect id in the callback
     if (data.json.menuitem in this._ctxHandlers) {
       this._ctxHandlers[data.json.menuitem].click();
       this._ctxHandlers = {};
     } else {
       debug("Ignored invalid contextmenu invocation");
     }
   },
   _buildMenuObj: function(menu, idPrefix) {
     function maybeCopyAttribute(src, target, attribute) {
       if (src.getAttribute(attribute)) {
         target[attribute] = src.getAttribute(attribute);
       }
     }
     var menuObj = {type: 'menu', items: []};
     maybeCopyAttribute(menu, menuObj, 'label');
     for (var i = 0, child; child = menu.children[i++];) {
       if (child.nodeName === 'MENU') {
         menuObj.items.push(this._buildMenuObj(child, idPrefix + i + '_'));
       } else if (child.nodeName === 'MENUITEM') {
         var id = this._ctxCounter + '_' + idPrefix + i;
         var menuitem = {id: id, type: 'menuitem'};
         maybeCopyAttribute(child, menuitem, 'label');
         maybeCopyAttribute(child, menuitem, 'icon');
         this._ctxHandlers[id] = child;
         menuObj.items.push(menuitem);
       }
     }
     return menuObj;
   },
   _recvSetVisible: function(data) {
     debug("Received setVisible message: (" + data.json.visible + ")");
     if (this._forcedVisible == data.json.visible) {
       return;
     }
     this._forcedVisible = data.json.visible;
     this._updateVisibility();
   },
   _recvVisible: function(data) {
     sendAsyncMsg('got-visible', {
       id: data.json.id,
       successRv: docShell.isActive
     });
   },
   /**
    * Called when the window which contains this iframe becomes hidden or
    * visible.
    */
   _recvOwnerVisibilityChange: function(data) {
     debug("Received ownerVisibilityChange: (" + data.json.visible + ")");
     this._ownerVisible = data.json.visible;
     this._updateVisibility();
   },
   _updateVisibility: function() {
     var visible = this._forcedVisible && this._ownerVisible;
     if (docShell.isActive !== visible) {
       docShell.isActive = visible;
       sendAsyncMsg('visibilitychange', {visible: visible});
     }
   },
   _recvSendMouseEvent: function(data) {
     let json = data.json;
     let utils = content.QueryInterface(Ci.nsIInterfaceRequestor)
                        .getInterface(Ci.nsIDOMWindowUtils);
     utils.sendMouseEventToWindow(json.type, json.x, json.y, json.button,
                                  json.clickCount, json.modifiers);
   },
   _recvSendTouchEvent: function(data) {
     let json = data.json;
     let utils = content.QueryInterface(Ci.nsIInterfaceRequestor)
                        .getInterface(Ci.nsIDOMWindowUtils);
     utils.sendTouchEventToWindow(json.type, json.identifiers, json.touchesX,
                                  json.touchesY, json.radiisX, json.radiisY,
                                  json.rotationAngles, json.forces, json.count,
                                  json.modifiers);
   },
   _recvCanGoBack: function(data) {
     var webNav = docShell.QueryInterface(Ci.nsIWebNavigation);
     sendAsyncMsg('got-can-go-back', {
       id: data.json.id,
       successRv: webNav.canGoBack
     });
   },
   _recvCanGoForward: function(data) {
     var webNav = docShell.QueryInterface(Ci.nsIWebNavigation);
     sendAsyncMsg('got-can-go-forward', {
       id: data.json.id,
       successRv: webNav.canGoForward
     });
   },
   _recvGoBack: function(data) {
     try {
       docShell.QueryInterface(Ci.nsIWebNavigation).goBack();
     } catch(e) {
       // Silently swallow errors; these happen when we can't go back.
     }
   },
   _recvGoForward: function(data) {
     try {
       docShell.QueryInterface(Ci.nsIWebNavigation).goForward();
     } catch(e) {
       // Silently swallow errors; these happen when we can't go forward.
     }
   },
   _recvReload: function(data) {
     let webNav = docShell.QueryInterface(Ci.nsIWebNavigation);
     let reloadFlags = data.json.hardReload ?
       webNav.LOAD_FLAGS_BYPASS_PROXY | webNav.LOAD_FLAGS_BYPASS_CACHE :
       webNav.LOAD_FLAGS_NONE;
     try {
       webNav.reload(reloadFlags);
     } catch(e) {
       // Silently swallow errors; these can happen if a used cancels reload
     }
   },
   _recvStop: function(data) {
     let webNav = docShell.QueryInterface(Ci.nsIWebNavigation);
     webNav.stop(webNav.STOP_NETWORK);
   },
   _recvSetInputMethodActive: function(data) {
     let msgData = { id: data.json.id };
     if (!this._isContentWindowCreated) {
       if (data.json.args.isActive) {
         // To activate the input method, we should wait before the content
         // window is ready.
         this._pendingSetInputMethodActive.push(data);
         return;
       }
       msgData.successRv = null;
       sendAsyncMsg('got-set-input-method-active', msgData);
       return;
     }
     // Unwrap to access webpage content.
     let nav = XPCNativeWrapper.unwrap(content.document.defaultView.navigator);
     if (nav.mozInputMethod) {
       // Wrap to access the chrome-only attribute setActive.
       new XPCNativeWrapper(nav.mozInputMethod).setActive(data.json.args.isActive);
       msgData.successRv = null;
     } else {
       msgData.errorMsg = 'Cannot access mozInputMethod.';
     }
     sendAsyncMsg('got-set-input-method-active', msgData);
   },
   _keyEventHandler: function(e) {
     if (whitelistedEvents.indexOf(e.keyCode) != -1 && !e.defaultPrevented) {
       sendAsyncMsg('keyevent', {
         type: e.type,
         keyCode: e.keyCode,
         charCode: e.charCode,
       });
     }
   },
   // The docShell keeps a weak reference to the progress listener, so we need
   // to keep a strong ref to it ourselves.
   _progressListener: {
     QueryInterface: XPCOMUtils.generateQI([Ci.nsIWebProgressListener,
                                            Ci.nsISupportsWeakReference]),
     _seenLoadStart: false,
     onLocationChange: function(webProgress, request, location, flags) {
       // We get progress events from subshells here, which is kind of weird.
       if (webProgress != docShell) {
         return;
       }
       // Ignore locationchange events which occur before the first loadstart.
       // These are usually about:blank loads we don't care about.
       if (!this._seenLoadStart) {
         return;
       }
       // Remove password and wyciwyg from uri.
       location = Cc["@mozilla.org/docshell/urifixup;1"]
         .getService(Ci.nsIURIFixup).createExposableURI(location);
       sendAsyncMsg('locationchange', { _payload_: location.spec });
     },
     onStateChange: function(webProgress, request, stateFlags, status) {
       if (webProgress != docShell) {
         return;
       }
       if (stateFlags & Ci.nsIWebProgressListener.STATE_START) {
         this._seenLoadStart = true;
         sendAsyncMsg('loadstart');
       }
       if (stateFlags & Ci.nsIWebProgressListener.STATE_STOP) {
         let bgColor = 'transparent';
         try {
           bgColor = content.getComputedStyle(content.document.body)
                            .getPropertyValue('background-color');
         } catch (e) {}
         sendAsyncMsg('loadend', {backgroundColor: bgColor});
         // Ignoring NS_BINDING_ABORTED, which is set when loading page is
         // stopped.
         if (status == Cr.NS_OK ||
             status == Cr.NS_BINDING_ABORTED) {
           return;
         }
         if (NS_ERROR_GET_MODULE(status) == NS_ERROR_MODULE_SECURITY &&
             getErrorClass(status) == Ci.nsINSSErrorsService.ERROR_CLASS_BAD_CERT) {
           // XXX Is there a point firing the event if the error page is not
           // certerror? If yes, maybe we should add a property to the
           // event to to indicate whether there is a custom page. That would
           // let the embedder have more control over the desired behavior.
           var errorPage = null;
           try {
             errorPage = Services.prefs.getCharPref(CERTIFICATE_ERROR_PAGE_PREF);
           } catch(e) {}
           if (errorPage == 'certerror') {
             sendAsyncMsg('error', { type: 'certerror' });
             return;
           }
         }
         // TODO See nsDocShell::DisplayLoadError for a list of all the error
         // codes (the status param) we should eventually handle here.
         sendAsyncMsg('error', { type: 'other' });
       }
     },
     onSecurityChange: function(webProgress, request, state) {
       if (webProgress != docShell) {
         return;
       }
       var stateDesc;
       if (state & Ci.nsIWebProgressListener.STATE_IS_SECURE) {
         stateDesc = 'secure';
       }
       else if (state & Ci.nsIWebProgressListener.STATE_IS_BROKEN) {
         stateDesc = 'broken';
       }
       else if (state & Ci.nsIWebProgressListener.STATE_IS_INSECURE) {
         stateDesc = 'insecure';
       }
       else {
         debug("Unexpected securitychange state!");
         stateDesc = '???';
       }
       // XXX Until bug 764496 is fixed, this will always return false.
       var isEV = !!(state & Ci.nsIWebProgressListener.STATE_IDENTITY_EV_TOPLEVEL);
       sendAsyncMsg('securitychange', { state: stateDesc, extendedValidation: isEV });
     },
     onStatusChange: function(webProgress, request, status, message) {},
     onProgressChange: function(webProgress, request, curSelfProgress,
                                maxSelfProgress, curTotalProgress, maxTotalProgress) {},
   },
   // Expose the message manager for WebApps and others.
   _messageManagerPublic: {
     sendAsyncMessage: global.sendAsyncMessage.bind(global),
     sendSyncMessage: global.sendSyncMessage.bind(global),
     addMessageListener: global.addMessageListener.bind(global),
     removeMessageListener: global.removeMessageListener.bind(global)
   },
   get messageManager() {
     return this._messageManagerPublic;
   }
 };
 var api = new BrowserElementChild();