Add a Create method to DesktopNotificationHandler and stubs for the notification objects.

chrome/browser/desktop_notification_handler.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_DESKTOP_NOTIFICATION_HANDLER_H_
 #define CHROME_BROWSER_DESKTOP_NOTIFICATION_HANDLER_H_
 #pragma once
 
 #include "content/browser/renderer_host/render_view_host_observer.h"
 
 class GURL;
 struct DesktopNotificationHostMsg_Show_Params;
 
 // Per-tab Desktop notification handler. Handles desktop notification IPCs
 // coming in from the renderer.
 class DesktopNotificationHandler : public RenderViewHostObserver {
  public:
-  explicit DesktopNotificationHandler(RenderViewHost* render_view_host);
+  static DesktopNotificationHandler* Create(RenderViewHost* render_view_host);
   virtual ~DesktopNotificationHandler();
 
  private:
+  explicit DesktopNotificationHandler(RenderViewHost* render_view_host);
+
   // RenderViewHostObserver implementation.
   virtual bool OnMessageReceived(const IPC::Message& message);
 
   // IPC handlers.
   void OnShow(const DesktopNotificationHostMsg_Show_Params& params);
   void OnCancel(int notification_id);
   void OnRequestPermission(const GURL& origin, int callback_id);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DesktopNotificationHandler);
 };
 
 #endif  // CHROME_BROWSER_DESKTOP_NOTIFICATION_HANDLER_H_