ppapi: Cleanup class/struct forward declarations

ppapi/proxy/serialized_flash_menu.h

 // Copyright (c) 2012 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 PPAPI_PROXY_SERIALIZED_FLASH_MENU_H_
 #define PPAPI_PROXY_SERIALIZED_FLASH_MENU_H_
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "ppapi/proxy/ppapi_proxy_export.h"
 
 namespace base {
 class Pickle;
 class PickleIterator;
 }
 
 struct PP_Flash_Menu;
 
-namespace IPC {
-class Message;
-}
-
 namespace ppapi {
 namespace proxy {
 
 class PPAPI_PROXY_EXPORT SerializedFlashMenu {
  public:
   SerializedFlashMenu();
   ~SerializedFlashMenu();
 
   bool SetPPMenu(const PP_Flash_Menu* menu);
 
   const PP_Flash_Menu* pp_menu() const { return pp_menu_; }
 
   void WriteToMessage(base::Pickle* m) const;
   bool ReadFromMessage(const base::Pickle* m, base::PickleIterator* iter);
 
  private:
   const PP_Flash_Menu* pp_menu_;
   bool own_menu_;
   DISALLOW_COPY_AND_ASSIGN(SerializedFlashMenu);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_SERIALIZED_FLASH_MENU_H_