diff -r 000000000000 -r 6474c204b198 dom/browser-element/BrowserElementParent.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/browser-element/BrowserElementParent.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,129 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {utils: Cu, interfaces: Ci} = Components;
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+const NS_PREFBRANCH_PREFCHANGE_TOPIC_ID = "nsPref:changed";
+const BROWSER_FRAMES_ENABLED_PREF = "dom.mozBrowserFramesEnabled";
+
+XPCOMUtils.defineLazyModuleGetter(this, "BrowserElementParentBuilder",
+                                  "resource://gre/modules/BrowserElementParent.jsm",
+                                  "BrowserElementParentBuilder");
+
+function debug(msg) {
+  //dump("BrowserElementParent.js - " + msg + "\n");
+}
+
+/**
+ * BrowserElementParent implements one half of <iframe mozbrowser>.  (The other
+ * half is, unsurprisingly, BrowserElementChild.)
+ *
+ * BrowserElementParentFactory detects when we create a windows or docshell
+ * contained inside a <iframe mozbrowser> and creates a BrowserElementParent
+ * object for that window.
+ *
+ * It creates a BrowserElementParent that injects script to listen for
+ * certain event.
+ */
+
+function BrowserElementParentFactory() {
+  this._initialized = false;
+}
+
+BrowserElementParentFactory.prototype = {
+  classID: Components.ID("{ddeafdac-cb39-47c4-9cb8-c9027ee36d26}"),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver,
+                                         Ci.nsISupportsWeakReference]),
+
+  /**
+   * Called on app startup, and also when the browser frames enabled pref is
+   * changed.
+   */
+  _init: function() {
+    if (this._initialized) {
+      return;
+    }
+
+    // If the pref is disabled, do nothing except wait for the pref to change.
+    // (This is important for tests, if nothing else.)
+    if (!this._browserFramesPrefEnabled()) {
+      Services.prefs.addObserver(BROWSER_FRAMES_ENABLED_PREF, this, /* ownsWeak = */ true);
+      return;
+    }
+
+    debug("_init");
+    this._initialized = true;
+
+    // Maps frame elements to BrowserElementParent objects.  We never look up
+    // anything in this map; the purpose is to keep the BrowserElementParent
+    // alive for as long as its frame element lives.
+    this._bepMap = new WeakMap();
+
+    Services.obs.addObserver(this, 'remote-browser-pending', /* ownsWeak = */ true);
+    Services.obs.addObserver(this, 'inprocess-browser-shown', /* ownsWeak = */ true);
+  },
+
+  _browserFramesPrefEnabled: function() {
+    try {
+      return Services.prefs.getBoolPref(BROWSER_FRAMES_ENABLED_PREF);
+    }
+    catch(e) {
+      return false;
+    }
+  },
+
+  _observeInProcessBrowserFrameShown: function(frameLoader) {
+    // Ignore notifications that aren't from a BrowserOrApp
+    if (!frameLoader.QueryInterface(Ci.nsIFrameLoader).ownerIsBrowserOrAppFrame) {
+      return;
+    }
+    debug("In-process browser frame shown " + frameLoader);
+    this._createBrowserElementParent(frameLoader,
+                                     /* hasRemoteFrame = */ false,
+                                     /* pending frame */ false);
+  },
+
+  _observeRemoteBrowserFramePending: function(frameLoader) {
+    // Ignore notifications that aren't from a BrowserOrApp
+    if (!frameLoader.QueryInterface(Ci.nsIFrameLoader).ownerIsBrowserOrAppFrame) {
+      return;
+    }
+    debug("Remote browser frame shown " + frameLoader);
+    this._createBrowserElementParent(frameLoader,
+                                     /* hasRemoteFrame = */ true,
+                                     /* pending frame */ true);
+  },
+
+  _createBrowserElementParent: function(frameLoader, hasRemoteFrame, isPendingFrame) {
+    let frameElement = frameLoader.QueryInterface(Ci.nsIFrameLoader).ownerElement;
+    this._bepMap.set(frameElement, BrowserElementParentBuilder.create(
+      frameLoader, hasRemoteFrame, isPendingFrame));
+  },
+
+  observe: function(subject, topic, data) {
+    switch(topic) {
+    case 'app-startup':
+      this._init();
+      break;
+    case NS_PREFBRANCH_PREFCHANGE_TOPIC_ID:
+      if (data == BROWSER_FRAMES_ENABLED_PREF) {
+        this._init();
+      }
+      break;
+    case 'remote-browser-pending':
+      this._observeRemoteBrowserFramePending(subject);
+      break;
+    case 'inprocess-browser-shown':
+      this._observeInProcessBrowserFrameShown(subject);
+      break;
+    }
+  },
+};
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([BrowserElementParentFactory]);