Fixes issues when switching between software and compositing.

content/renderer/browser_plugin/browser_plugin_compositing_helper.h

 // Copyright (c) 2013 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  CONTENT_RENDERER_BROWSER_PLUGIN_BROWSER_PLUGIN_COMPOSITING_HELPER_H_
 #define  CONTENT_RENDERER_BROWSER_PLUGIN_BROWSER_PLUGIN_COMPOSITING_HELPER_H_
 
 #include <string>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/common/content_export.h"
 #include "ui/gfx/size.h"
 
 namespace cc {
 class TextureLayer;
 }
 
 namespace WebKit {
 class WebPluginContainer;
 class WebLayer;
 }
 
 namespace content {
 
-class CONTENT_EXPORT BrowserPluginCompositingHelper {
+class CONTENT_EXPORT BrowserPluginCompositingHelper :
+    public base::RefCounted<BrowserPluginCompositingHelper> {
  public:
   BrowserPluginCompositingHelper(WebKit::WebPluginContainer* container,
                                  int host_routing_id);
-  ~BrowserPluginCompositingHelper();
-
   void EnableCompositing(bool);
+  void OnContainerDestroy();
   void OnBuffersSwapped(const gfx::Size& size,
                         const std::string& mailbox_name,
                         int gpu_route_id,
                         int gpu_host_id);
   void SetContainerSize(const gfx::Size&);
-
+ protected:
+  // Friend RefCounted so that the dtor can be non-public.
+  friend class base::RefCounted<BrowserPluginCompositingHelper>;
  private:
+  ~BrowserPluginCompositingHelper();
+  void FreeMailboxMemory(const std::string& mailbox_name);
+  void MailboxReleased(const std::string& mailbox_name,
+                       int gpu_route_id,
+                       int gpu_host_id,
+                       unsigned sync_point);
   void UpdateUVRect();
 
   int host_routing_id_;
   bool last_mailbox_valid_;
+  bool ack_pending_;
 
   gfx::Size buffer_size_;
   gfx::Size container_size_;
 
   scoped_refptr<cc::TextureLayer> texture_layer_;
   scoped_ptr<WebKit::WebLayer> web_layer_;
   WebKit::WebPluginContainer* container_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_BROWSER_PLUGIN_BROWSER_PLUGIN_COMPOSITING_HELPER_H_