Refactor gpu::Buffer to allow different types of backing

gpu/command_buffer/service/command_buffer_service.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 GPU_COMMAND_BUFFER_SERVICE_COMMAND_BUFFER_SERVICE_H_
 #define GPU_COMMAND_BUFFER_SERVICE_COMMAND_BUFFER_SERVICE_H_
 
 #include "base/callback.h"
 #include "base/memory/shared_memory.h"
 #include "gpu/command_buffer/common/command_buffer.h"
@@ skipping 61 matching lines @@
   // writer a means of waiting for the reader to make some progress before
   // attempting to write more to the command buffer. Takes ownership of
   // callback.
   virtual void SetPutOffsetChangeCallback(const base::Closure& callback);
   // Sets a callback that is called whenever the get buffer is changed.
   virtual void SetGetBufferChangeCallback(
       const GetBufferChangedCallback& callback);
   virtual void SetParseErrorCallback(const base::Closure& callback);
 
   // Setup the shared memory that shared state should be copied into.
-  bool SetSharedStateBuffer(scoped_ptr<base::SharedMemory> shared_state_shm);
+  void SetSharedStateBuffer(scoped_ptr<BufferBacking> shared_state_buffer);
 
   // Copy the current state into the shared state transfer buffer.
   void UpdateState();
 
-  // Register an existing shared memory object and get an ID that can be used
-  // to identify it in the command buffer. Callee dups the handle until
-  // DestroyTransferBuffer is called.
-  bool RegisterTransferBuffer(int32 id,
-                              scoped_ptr<base::SharedMemory> shared_memory,
-                              size_t size);
+  // Registers an existing shared memory object and get an ID that can be used
+  // to identify it in the command buffer.
+  bool RegisterTransferBuffer(int32 id, scoped_ptr<BufferBacking> buffer);
 
  private:
   int32 ring_buffer_id_;
   scoped_refptr<Buffer> ring_buffer_;
-  scoped_ptr<base::SharedMemory> shared_state_shm_;
+  scoped_ptr<BufferBacking> shared_state_buffer_;
   CommandBufferSharedState* shared_state_;
   int32 num_entries_;
   int32 get_offset_;
   int32 put_offset_;
   base::Closure put_offset_change_callback_;
   GetBufferChangedCallback get_buffer_change_callback_;
   base::Closure parse_error_callback_;
   TransferBufferManagerInterface* transfer_buffer_manager_;
   int32 token_;
   uint32 generation_;
   error::Error error_;
   error::ContextLostReason context_lost_reason_;
 
   DISALLOW_COPY_AND_ASSIGN(CommandBufferService);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_COMMAND_BUFFER_SERVICE_H_