--- a/browser/components/sidebar/nsSidebar.js
+++ b/browser/components/sidebar/nsSidebar.js
@@ -5,19 +5,16 @@
 
 Components.utils.import("resource://gre/modules/Services.jsm");
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 const DEBUG = false; /* set to false to suppress debug messages */
 
 const SIDEBAR_CONTRACTID        = "@mozilla.org/sidebar;1";
 const SIDEBAR_CID               = Components.ID("{22117140-9c6e-11d3-aaf1-00805f8a4905}");
-const nsISidebar                = Components.interfaces.nsISidebar;
-const nsISidebarExternal        = Components.interfaces.nsISidebarExternal;
-const nsIClassInfo              = Components.interfaces.nsIClassInfo;
 
 // File extension for Sherlock search plugin description files
 const SHERLOCK_FILE_EXT_REGEXP = /\.src$/i;
 
 function nsSidebar()
 {
 }
 
@@ -114,23 +111,17 @@ function (aDescriptionURL)
 // http://msdn.microsoft.com/en-us/library/aa342526%28VS.85%29.aspx .
 // XXX Implement this!
 nsSidebar.prototype.IsSearchProviderInstalled =
 function (aSearchURL)
 {
   return 0;
 }
 
-nsSidebar.prototype.classInfo = XPCOMUtils.generateCI({classID: SIDEBAR_CID,
-                                                       contractID: SIDEBAR_CONTRACTID,
-                                                       classDescription: "Sidebar",
-                                                       interfaces: [nsISidebar, nsISidebarExternal],
-                                                       flags: nsIClassInfo.DOM_OBJECT});
-
-nsSidebar.prototype.QueryInterface = XPCOMUtils.generateQI([nsISidebar, nsISidebarExternal]);
+nsSidebar.prototype.QueryInterface = XPCOMUtils.generateQI([Components.interfaces.nsISupports]);
 
 this.NSGetFactory = XPCOMUtils.generateNSGetFactory([nsSidebar]);
 
 /* static functions */
 if (DEBUG)
     debug = function (s) { dump("-*- sidebar component: " + s + "\n"); }
 else
     debug = function (s) {}

--- a/browser/components/sidebar/nsSidebar.manifest
+++ b/browser/components/sidebar/nsSidebar.manifest
@@ -1,4 +1,2 @@
 component {22117140-9c6e-11d3-aaf1-00805f8a4905} nsSidebar.js
 contract @mozilla.org/sidebar;1 {22117140-9c6e-11d3-aaf1-00805f8a4905}
-category JavaScript-global-property sidebar @mozilla.org/sidebar;1
-category JavaScript-global-property external @mozilla.org/sidebar;1

--- a/browser/metro/components/Sidebar.js
+++ b/browser/metro/components/Sidebar.js
@@ -64,17 +64,16 @@ Sidebar.prototype = {
                                                   [brandName], 1);
       Services.prompt.alert(null, title, msg);
       return false;
     }
     
     return true;
   },
 
-  // =========================== nsISidebar ===========================
   // The suggestedTitle and suggestedCategory parameters are ignored, but remain
   // for backward compatibility.
   addSearchEngine: function addSearchEngine(engineURL, iconURL, suggestedTitle,
                                             suggestedCategory) {
     if (!this._validateSearchEngine(engineURL, iconURL))
       return;
 
     // File extension for Sherlock search plugin description files
@@ -87,17 +86,16 @@ Sidebar.prototype = {
     if (SHERLOCK_FILE_EXT_REGEXP.test(engineURL))
       dataType = Ci.nsISearchEngine.DATA_TEXT;
     else
       dataType = Ci.nsISearchEngine.DATA_XML;
 
     Services.search.addEngine(engineURL, dataType, iconURL, true);
   },
 
-  // =========================== nsISidebarExternal ===========================
   // This function exists to implement window.external.AddSearchProvider(),
   // to match other browsers' APIs.  The capitalization, although nonstandard here,
   // is therefore important.
   AddSearchProvider: function AddSearchProvider(aDescriptionURL) {
     if (!this._validateSearchEngine(aDescriptionURL, ""))
       return;
 
     if (this.inContentProcess) {
@@ -117,25 +115,16 @@ Sidebar.prototype = {
   // stemming from difficulties in determining what domain issued the request.
   // See bug 340604 and
   // http://msdn.microsoft.com/en-us/library/aa342526%28VS.85%29.aspx .
   // XXX Implement this!
   IsSearchProviderInstalled: function IsSearchProviderInstalled(aSearchURL) {
     return 0;
   },
 
-  // =========================== nsIClassInfo ===========================
-  classInfo: XPCOMUtils.generateCI({classID: SIDEBAR_CID,
-                                    contractID: SIDEBAR_CONTRACTID,
-                                    interfaces: [Ci.nsISidebar,
-                                                 Ci.nsISidebarExternal],
-                                    flags: Ci.nsIClassInfo.DOM_OBJECT,
-                                    classDescription: "Sidebar"}),
-
   // =========================== nsISupports ===========================
-  QueryInterface: XPCOMUtils.generateQI([Ci.nsISidebar,
-                                         Ci.nsISidebarExternal]),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsISupports]),
 
   // XPCOMUtils stuff
   classID: SIDEBAR_CID,
 };
 
 this.NSGetFactory = XPCOMUtils.generateNSGetFactory([Sidebar]);

--- a/browser/metro/components/components.manifest
+++ b/browser/metro/components/components.manifest
@@ -17,18 +17,16 @@ contract @mozilla.org/network/protocol/a
 # DirectoryProvider.js
 component {ef0f7a87-c1ee-45a8-8d67-26f586e46a4b} DirectoryProvider.js
 contract @mozilla.org/browser/directory-provider;1 {ef0f7a87-c1ee-45a8-8d67-26f586e46a4b}
 category xpcom-directory-providers browser-directory-provider @mozilla.org/browser/directory-provider;1
 
 # Sidebar.js
 component {22117140-9c6e-11d3-aaf1-00805f8a4905} Sidebar.js
 contract @mozilla.org/sidebar;1 {22117140-9c6e-11d3-aaf1-00805f8a4905}
-category JavaScript-global-property sidebar @mozilla.org/sidebar;1
-category JavaScript-global-property external @mozilla.org/sidebar;1
 category wakeup-request Sidebar @mozilla.org/sidebar;1,nsISidebarExternal,getService,Sidebar:AddSearchProvider
 
 # SessionStore.js
 component {8c1f07d6-cba3-4226-a315-8bd43d67d032} SessionStore.js
 contract @mozilla.org/browser/sessionstore;1 {8c1f07d6-cba3-4226-a315-8bd43d67d032}
 category app-startup SessionStore service,@mozilla.org/browser/sessionstore;1
 
 # BrowserStartup.js

--- a/dom/base/moz.build
+++ b/dom/base/moz.build
@@ -169,8 +169,11 @@ FINAL_LIBRARY = 'gklayout'
 LOCAL_INCLUDES += [
     '/js/xpconnect/src',
     '/js/xpconnect/wrappers',
 ]
 
 for var in ('MOZ_JSDEBUGGER', 'MOZ_B2G_RIL', 'MOZ_B2G_FM'):
     if CONFIG[var]:
         DEFINES[var] = True
+
+if CONFIG['MOZ_BUILD_APP'] in ['browser', 'mobile/android', 'xulrunner']:
+    DEFINES['HAVE_SIDEBAR'] = True

--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -211,16 +211,19 @@
 #include "mozilla/dom/AudioContext.h"
 #include "mozilla/dom/BrowserElementDictionariesBinding.h"
 #include "mozilla/dom/Console.h"
 #include "mozilla/dom/FunctionBinding.h"
 #include "mozilla/dom/WindowBinding.h"
 #include "nsITabChild.h"
 #include "mozilla/dom/MediaQueryList.h"
 #include "mozilla/dom/ScriptSettings.h"
+#ifdef HAVE_SIDEBAR
+#include "mozilla/dom/ExternalBinding.h"
+#endif
 
 #ifdef MOZ_WEBSPEECH
 #include "mozilla/dom/SpeechSynthesis.h"
 #endif
 
 #ifdef MOZ_JSDEBUGGER
 #include "jsdIDebuggerService.h"
 #endif
@@ -1441,16 +1444,18 @@ nsGlobalWindow::CleanUp()
   mHistory = nullptr;
   mFrames = nullptr;
   mWindowUtils = nullptr;
   mApplicationCache = nullptr;
   mIndexedDB = nullptr;
 
   mConsole = nullptr;
 
+  mExternal = nullptr;
+
   mPerformance = nullptr;
 
 #ifdef MOZ_WEBSPEECH
   mSpeechSynthesis = nullptr;
 #endif
 
   ClearControllers();
 
@@ -1756,16 +1761,17 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mMenubar)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mToolbar)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mLocationbar)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPersonalbar)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mStatusbar)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mScrollbars)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCrypto)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mConsole)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mExternal)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsGlobalWindow)
   nsGlobalWindow::CleanupCachedXBLHandlers(tmp);
 
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mContext)
 
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mControllers)
@@ -1814,16 +1820,17 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(ns
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mMenubar)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mToolbar)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mLocationbar)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mPersonalbar)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mStatusbar)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mScrollbars)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mCrypto)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mConsole)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mExternal)
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 #ifdef DEBUG
 void
 nsGlobalWindow::RiskyUnlink()
 {
   NS_CYCLE_COLLECTION_INNERNAME.Unlink(this);
 }
@@ -13492,16 +13499,64 @@ nsGlobalWindow::GetConsole(ErrorResult& 
 
   if (!mConsole) {
     mConsole = new Console(this);
   }
 
   return mConsole;
 }
 
+already_AddRefed<External>
+nsGlobalWindow::GetExternal(ErrorResult& aRv)
+{
+  FORWARD_TO_INNER_OR_THROW(GetExternal, (aRv), aRv, nullptr);
+
+#ifdef HAVE_SIDEBAR
+  if (!mExternal) {
+    AutoJSContext cx;
+    JS::Rooted<JSObject*> jsImplObj(cx);
+    ConstructJSImplementation(cx, "@mozilla.org/sidebar;1",
+                              this, &jsImplObj, aRv);
+    if (aRv.Failed()) {
+      return nullptr;
+    }
+    mExternal = new External(jsImplObj, this);
+  }
+
+  nsRefPtr<External> external = static_cast<External*>(mExternal.get());
+  return external.forget();
+#else
+  aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
+  return nullptr;
+#endif
+}
+
+void
+nsGlobalWindow::GetSidebar(OwningExternalOrWindowProxy& aResult,
+                           ErrorResult& aRv)
+{
+  FORWARD_TO_INNER_OR_THROW(GetSidebar, (aResult, aRv), aRv, );
+
+#ifdef HAVE_SIDEBAR
+  // First check for a named frame named "sidebar"
+  nsCOMPtr<nsIDOMWindow> domWindow = GetChildWindow(NS_LITERAL_STRING("sidebar"));
+  if (domWindow) {
+    aResult.SetAsWindowProxy() = domWindow.forget();
+    return;
+  }
+
+  nsRefPtr<External> external = GetExternal(aRv);
+  if (external) {
+    aResult.SetAsExternal() = external;
+  }
+#else
+  aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
+#endif
+}
+
 #ifdef MOZ_B2G
 void
 nsGlobalWindow::EnableNetworkEvent(uint32_t aType)
 {
   MOZ_ASSERT(IsInnerWindow());
 
   nsCOMPtr<nsIPermissionManager> permMgr =
     do_GetService(NS_PERMISSIONMANAGER_CONTRACTID);

--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -102,20 +102,22 @@ struct nsRect;
 
 class nsWindowSizes;
 
 namespace mozilla {
 class Selection;
 namespace dom {
 class BarProp;
 class Console;
+class External;
 class Function;
 class Gamepad;
 class MediaQueryList;
 class Navigator;
+class OwningExternalOrWindowProxy;
 class SpeechSynthesis;
 class WakeLock;
 namespace indexedDB {
 class IDBFactory;
 } // namespace indexedDB
 } // namespace dom
 } // namespace mozilla
 
@@ -818,16 +820,20 @@ public:
                                       const nsAString& aName,
                                       const nsAString& aOptions,
                                       mozilla::ErrorResult& aError);
   mozilla::dom::Navigator* GetNavigator(mozilla::ErrorResult& aError);
   nsIDOMOfflineResourceList* GetApplicationCache(mozilla::ErrorResult& aError);
 
   mozilla::dom::Console* GetConsole(mozilla::ErrorResult& aRv);
 
+  void GetSidebar(mozilla::dom::OwningExternalOrWindowProxy& aResult,
+                  mozilla::ErrorResult& aRv);
+  already_AddRefed<mozilla::dom::External> GetExternal(mozilla::ErrorResult& aRv);
+
 protected:
   bool AlertOrConfirm(bool aAlert, const nsAString& aMessage,
                       mozilla::ErrorResult& aError);
 
 public:
   void Alert(const nsAString& aMessage, mozilla::ErrorResult& aError);
   bool Confirm(const nsAString& aMessage, mozilla::ErrorResult& aError);
   void Prompt(const nsAString& aMessage, const nsAString& aInitial,
@@ -1450,16 +1456,21 @@ protected:
   nsRefPtr<mozilla::dom::BarProp> mStatusbar;
   nsRefPtr<mozilla::dom::BarProp> mScrollbars;
   nsRefPtr<nsDOMWindowUtils>    mWindowUtils;
   nsString                      mStatus;
   nsString                      mDefaultStatus;
   nsGlobalWindowObserver*       mObserver; // Inner windows only.
   nsCOMPtr<nsIDOMCrypto>        mCrypto;
   nsRefPtr<mozilla::dom::Console> mConsole;
+  // We need to store an nsISupports pointer to this object because the
+  // mozilla::dom::External class doesn't exist on b2g and using the type
+  // forward declared here means that ~nsGlobalWindow wouldn't compile because
+  // it wouldn't see the ~External function's declaration.
+  nsCOMPtr<nsISupports>         mExternal;
 
   nsCOMPtr<nsIDOMStorage>      mLocalStorage;
   nsCOMPtr<nsIDOMStorage>      mSessionStorage;
 
   nsCOMPtr<nsIXPConnectJSObjectHolder> mInnerWindowHolder;
 
   // These member variable are used only on inner windows.
   nsRefPtr<mozilla::EventListenerManager> mListenerManager;

--- a/dom/bindings/BindingUtils.cpp
+++ b/dom/bindings/BindingUtils.cpp
@@ -1983,63 +1983,74 @@ ConstructJSImplementation(JSContext* aCx
 {
   // Get the window to use as a parent and for initialization.
   nsCOMPtr<nsPIDOMWindow> window = do_QueryInterface(aGlobal.GetAsSupports());
   if (!window) {
     aRv.Throw(NS_ERROR_FAILURE);
     return nullptr;
   }
 
+  ConstructJSImplementation(aCx, aContractId, window, aObject, aRv);
+
+  if (aRv.Failed()) {
+    return nullptr;
+  }
+  return window.forget();
+}
+
+void
+ConstructJSImplementation(JSContext* aCx, const char* aContractId,
+                          nsPIDOMWindow* aWindow,
+                          JS::MutableHandle<JSObject*> aObject,
+                          ErrorResult& aRv)
+{
   // Make sure to divorce ourselves from the calling JS while creating and
   // initializing the object, so exceptions from that will get reported
   // properly, since those are never exceptions that a spec wants to be thrown.
   {
     AutoSystemCaller asc;
 
     // Get the XPCOM component containing the JS implementation.
     nsCOMPtr<nsISupports> implISupports = do_CreateInstance(aContractId);
     if (!implISupports) {
       NS_WARNING("Failed to get JS implementation for contract");
       aRv.Throw(NS_ERROR_FAILURE);
-      return nullptr;
+      return;
     }
     // Initialize the object, if it implements nsIDOMGlobalPropertyInitializer.
     nsCOMPtr<nsIDOMGlobalPropertyInitializer> gpi =
       do_QueryInterface(implISupports);
     if (gpi) {
       JS::Rooted<JS::Value> initReturn(aCx);
-      nsresult rv = gpi->Init(window, &initReturn);
+      nsresult rv = gpi->Init(aWindow, &initReturn);
       if (NS_FAILED(rv)) {
         aRv.Throw(rv);
-        return nullptr;
+        return;
       }
       // With JS-implemented WebIDL, the return value of init() is not used to determine
       // if init() failed, so init() should only return undefined. Any kind of permission
       // or pref checking must happen by adding an attribute to the WebIDL interface.
       if (!initReturn.isUndefined()) {
         MOZ_ASSERT(false, "The init() method for JS-implemented WebIDL should not return anything");
         MOZ_CRASH();
       }
     }
     // Extract the JS implementation from the XPCOM object.
     nsCOMPtr<nsIXPConnectWrappedJS> implWrapped =
       do_QueryInterface(implISupports);
     MOZ_ASSERT(implWrapped, "Failed to get wrapped JS from XPCOM component.");
     if (!implWrapped) {
       aRv.Throw(NS_ERROR_FAILURE);
-      return nullptr;
+      return;
     }
     aObject.set(implWrapped->GetJSObject());
     if (!aObject) {
       aRv.Throw(NS_ERROR_FAILURE);
-      return nullptr;
     }
   }
-
-  return window.forget();
 }
 
 bool
 NonVoidByteStringToJsval(JSContext *cx, const nsACString &str,
                          JS::MutableHandle<JS::Value> rval)
 {
     // ByteStrings are not UTF-8 encoded.
     JSString* jsStr = JS_NewStringCopyN(cx, str.Data(), str.Length());

--- a/dom/bindings/BindingUtils.h
+++ b/dom/bindings/BindingUtils.h
@@ -2288,16 +2288,22 @@ GetUnforgeableHolder(JSObject* aGlobal, 
 
 // Given a JSObject* that represents the chrome side of a JS-implemented WebIDL
 // interface, get the nsPIDOMWindow corresponding to the content side, if any.
 // A false return means an exception was thrown.
 bool
 GetWindowForJSImplementedObject(JSContext* cx, JS::Handle<JSObject*> obj,
                                 nsPIDOMWindow** window);
 
+void
+ConstructJSImplementation(JSContext* aCx, const char* aContractId,
+                          nsPIDOMWindow* aWindow,
+                          JS::MutableHandle<JSObject*> aObject,
+                          ErrorResult& aRv);
+
 already_AddRefed<nsPIDOMWindow>
 ConstructJSImplementation(JSContext* aCx, const char* aContractId,
                           const GlobalObject& aGlobal,
                           JS::MutableHandle<JSObject*> aObject,
                           ErrorResult& aRv);
 
 /**
  * Convert an nsCString to jsval, returning true on success.

--- a/dom/bindings/moz.build
+++ b/dom/bindings/moz.build
@@ -85,8 +85,12 @@ if CONFIG['MOZ_AUDIO_CHANNEL_MANAGER']:
     LOCAL_INCLUDES += [
         '/dom/system/gonk',
     ]
 
 FINAL_LIBRARY = 'xul'
 
 SPHINX_TREES['webidl'] = 'docs'
 SPHINX_PYTHON_PACKAGE_DIRS += ['mozwebidlcodegen']
+
+if CONFIG['MOZ_BUILD_APP'] in ['browser', 'mobile/android', 'xulrunner']:
+    # This is needed for Window.webidl
+    DEFINES['HAVE_SIDEBAR'] = True

--- a/dom/interfaces/sidebar/moz.build
+++ b/dom/interfaces/sidebar/moz.build
@@ -1,13 +1,12 @@
 # -*- Mode: python; c-basic-offset: 4; 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/.
 
 XPIDL_SOURCES += [
-    'nsISidebar.idl',
     'nsIWebContentHandlerRegistrar.idl',
 ]
 
 XPIDL_MODULE = 'dom_sidebar'
 

deleted file mode 100644
--- a/dom/interfaces/sidebar/nsISidebar.idl
+++ /dev/null
@@ -1,29 +0,0 @@
-/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
- *
- * 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/. */
-
-#include "nsISupports.idl"
-
-[scriptable, uuid(351887ca-56b2-4458-96fc-88baeb57b6e7)]
-interface nsISidebar : nsISupports
-{
-  void addSearchEngine(in DOMString engineURL, in DOMString iconURL,
-                       in DOMString suggestedTitle, in DOMString suggestedCategory);
-};
-
-[scriptable, uuid(5895076f-e28e-434a-9fdb-a69f94eb323f)]
-interface nsISidebarExternal : nsISupports
-{
-  void AddSearchProvider(in DOMString aDescriptionURL);
-  unsigned long IsSearchProviderInstalled(in DOMString aSearchURL);
-};
-
-%{ C++
-// {577CB744-8CAF-11d3-AAEF-00805F8A4905} 
-#define NS_SIDEBAR_CID \
-{ 0x577cb744, 0x8caf, 0x11d3, { 0xaa, 0xef, 0x0, 0x80, 0x5f, 0x8a, 0x49, 0x5 } }
-
-#define NS_SIDEBAR_CONTRACTID "@mozilla.org/sidebar;1"
-%}

--- a/dom/tests/mochitest/bugs/test_bug857555.html
+++ b/dom/tests/mochitest/bugs/test_bug857555.html
@@ -11,25 +11,23 @@ https://bugzilla.mozilla.org/show_bug.cg
   <script type="application/javascript">
 
   /** Test for Bug 857555 **/
   SimpleTest.waitForExplicitFinish();
 
   addLoadEvent(function() {
     is(content, $("t").contentWindow, "'content' as iframe name should work");
     is(sidebar, $("u").contentWindow, "'sidebar' as iframe name should work");
-    is(external, $("v").contentWindow, "'external' as iframe name should work");
     SimpleTest.finish();
   });
   </script>
 </head>
 <body>
 <a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=857555">Mozilla Bug 857555</a>
 <p id="display"></p>
 <div id="content" style="display: none">
   <iframe name="content" id="t"></iframe>
   <iframe name="sidebar" id="u"></iframe>
-  <iframe name="external" id="v"></iframe>
 </div>
 <pre id="test">
 </pre>
 </body>
 </html>

--- a/dom/tests/mochitest/general/test_interfaces.html
+++ b/dom/tests/mochitest/general/test_interfaces.html
@@ -343,16 +343,18 @@ var interfaceNamesInGlobalScope =
     "Event",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "EventListenerInfo",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "EventSource",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "EventTarget",
 // IMPORTANT: Do not change this list without review from a DOM peer!
+    {name: "External", b2g: false},
+// IMPORTANT: Do not change this list without review from a DOM peer!
     "File",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "FileHandle",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "FileList",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "FileReader",
 // IMPORTANT: Do not change this list without review from a DOM peer!

new file mode 100644
--- /dev/null
+++ b/dom/webidl/External.webidl
@@ -0,0 +1,18 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/.
+ */
+
+[JSImplementation="@mozilla.org/sidebar;1"]
+interface External
+{
+  void AddSearchProvider(DOMString aDescriptionURL);
+  unsigned long IsSearchProviderInstalled(DOMString aSearchURL);
+};
+
+// Mozilla extension
+partial interface External {
+  void addSearchEngine(DOMString engineURL, DOMString iconURL,
+                       DOMString suggestedTitle, DOMString suggestedCategory);
+};

--- a/dom/webidl/Window.webidl
+++ b/dom/webidl/Window.webidl
@@ -60,17 +60,19 @@ typedef any Transferable;
   [Throws] WindowProxy? open(optional DOMString url = "", optional DOMString target = "", optional DOMString features = "");
   // We think the indexed getter is a bug in the spec, it actually needs to live
   // on the WindowProxy
   //getter WindowProxy (unsigned long index);
   //getter object (DOMString name);
 
   // the user agent
   [Throws] readonly attribute Navigator navigator; 
-  //(Not implemented)readonly attribute External external;
+#ifdef HAVE_SIDEBAR
+  [Replaceable, Throws] readonly attribute External external;
+#endif
   [Throws] readonly attribute ApplicationCache applicationCache;
 
   // user prompts
   [Throws] void alert(optional DOMString message = "");
   [Throws] boolean confirm(optional DOMString message = "");
   [Throws] DOMString? prompt(optional DOMString message = "", optional DOMString default = "");
   [Throws] void print();
   //[Throws] any showModalDialog(DOMString url, optional any argument);
@@ -343,16 +345,23 @@ Window implements TouchEventHandlers;
 Window implements OnErrorEventHandlerForWindow;
 
 // ConsoleAPI
 partial interface Window {
   [Replaceable, GetterThrows]
   readonly attribute Console console;
 };
 
+#ifdef HAVE_SIDEBAR
+// Mozilla extension
+partial interface Window {
+  [Replaceable, Throws]
+  readonly attribute (External or WindowProxy) sidebar;
+};
+#endif
 
 [ChromeOnly] interface ChromeWindow {
   [Func="nsGlobalWindow::IsChromeWindow"]
   const unsigned short STATE_MAXIMIZED = 1;
   [Func="nsGlobalWindow::IsChromeWindow"]
   const unsigned short STATE_MINIMIZED = 2;
   [Func="nsGlobalWindow::IsChromeWindow"]
   const unsigned short STATE_NORMAL = 3;

--- a/dom/webidl/moz.build
+++ b/dom/webidl/moz.build
@@ -616,8 +616,13 @@ if CONFIG['MOZ_B2G_BT']:
         'BluetoothDeviceEvent.webidl',
         'BluetoothStatusChangedEvent.webidl',
     ]
 
 if CONFIG['MOZ_BUILD_APP'] in ['browser', 'xulrunner']:
     WEBIDL_FILES += [
         'BrowserFeedWriter.webidl',
     ]
+
+if CONFIG['MOZ_BUILD_APP'] in ['browser', 'mobile/android', 'xulrunner']:
+    WEBIDL_FILES += [
+        'External.webidl',
+    ]

--- a/mobile/android/components/MobileComponents.manifest
+++ b/mobile/android/components/MobileComponents.manifest
@@ -22,18 +22,16 @@ contract @mozilla.org/network/protocol/a
 # DirectoryProvider.js
 component {ef0f7a87-c1ee-45a8-8d67-26f586e46a4b} DirectoryProvider.js
 contract @mozilla.org/browser/directory-provider;1 {ef0f7a87-c1ee-45a8-8d67-26f586e46a4b}
 category xpcom-directory-providers browser-directory-provider @mozilla.org/browser/directory-provider;1
 
 # Sidebar.js
 component {22117140-9c6e-11d3-aaf1-00805f8a4905} Sidebar.js
 contract @mozilla.org/sidebar;1 {22117140-9c6e-11d3-aaf1-00805f8a4905}
-category JavaScript-global-property sidebar @mozilla.org/sidebar;1
-category JavaScript-global-property external @mozilla.org/sidebar;1
 category wakeup-request Sidebar @mozilla.org/sidebar;1,nsISidebarExternal,getService,Sidebar:AddSearchProvider
 
 # SessionStore.js
 component {8c1f07d6-cba3-4226-a315-8bd43d67d032} SessionStore.js
 contract @mozilla.org/browser/sessionstore;1 {8c1f07d6-cba3-4226-a315-8bd43d67d032}
 category app-startup SessionStore service,@mozilla.org/browser/sessionstore;1
 
 # stylesheets

--- a/mobile/android/components/Sidebar.js
+++ b/mobile/android/components/Sidebar.js
@@ -86,17 +86,16 @@ Sidebar.prototype = {
     if (SHERLOCK_FILE_EXT_REGEXP.test(engineURL))
       dataType = Ci.nsISearchEngine.DATA_TEXT;
     else
       dataType = Ci.nsISearchEngine.DATA_XML;
 
     Services.search.addEngine(engineURL, dataType, iconURL, true);
   },
 
-  // =========================== nsISidebarExternal ===========================
   // This function exists to implement window.external.AddSearchProvider(),
   // to match other browsers' APIs.  The capitalization, although nonstandard here,
   // is therefore important.
   AddSearchProvider: function AddSearchProvider(aDescriptionURL) {
     if (!this._validateSearchEngine(aDescriptionURL, ""))
       return;
 
     if (this.inContentProcess) {
@@ -116,25 +115,16 @@ Sidebar.prototype = {
   // stemming from difficulties in determining what domain issued the request.
   // See bug 340604 and
   // http://msdn.microsoft.com/en-us/library/aa342526%28VS.85%29.aspx .
   // XXX Implement this!
   IsSearchProviderInstalled: function IsSearchProviderInstalled(aSearchURL) {
     return 0;
   },
 
-  // =========================== nsIClassInfo ===========================
-  classInfo: XPCOMUtils.generateCI({classID: SIDEBAR_CID,
-                                    contractID: SIDEBAR_CONTRACTID,
-                                    interfaces: [Ci.nsISidebar,
-                                                 Ci.nsISidebarExternal],
-                                    flags: Ci.nsIClassInfo.DOM_OBJECT,
-                                    classDescription: "Sidebar"}),
-
   // =========================== nsISupports ===========================
-  QueryInterface: XPCOMUtils.generateQI([Ci.nsISidebar,
-                                         Ci.nsISidebarExternal]),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsISupports]),
 
   // XPCOMUtils stuff
   classID: SIDEBAR_CID,
 };
 
 this.NSGetFactory = XPCOMUtils.generateNSGetFactory([Sidebar]);