Refactor gpu::Buffer to allow different types of backing

gpu/command_buffer/service/transfer_buffer_manager.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_TRANSFER_BUFFER_MANAGER_H_
 #define GPU_COMMAND_BUFFER_SERVICE_TRANSFER_BUFFER_MANAGER_H_
 
 #include <set>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/containers/hash_tables.h"
 #include "base/memory/shared_memory.h"
 #include "gpu/command_buffer/common/command_buffer_shared.h"
 
 namespace gpu {
 
 class GPU_EXPORT TransferBufferManagerInterface {
  public:
   virtual ~TransferBufferManagerInterface();
 
-  virtual bool RegisterTransferBuffer(
-      int32 id,
-      scoped_ptr<base::SharedMemory> shared_memory,
-      size_t size) = 0;
+  virtual bool RegisterTransferBuffer(int32 id,
+                                      scoped_ptr<BufferBacking> buffer) = 0;
   virtual void DestroyTransferBuffer(int32 id) = 0;
   virtual scoped_refptr<Buffer> GetTransferBuffer(int32 id) = 0;
 };
 
 class GPU_EXPORT TransferBufferManager
     : public TransferBufferManagerInterface {
  public:
   TransferBufferManager();
 
   bool Initialize();
-  virtual bool RegisterTransferBuffer(
-      int32 id,
-      scoped_ptr<base::SharedMemory> shared_memory,
-      size_t size) OVERRIDE;
+  virtual bool RegisterTransferBuffer(int32 id,
+                                      scoped_ptr<BufferBacking> buffer_backing)
+      OVERRIDE;
   virtual void DestroyTransferBuffer(int32 id) OVERRIDE;
   virtual scoped_refptr<Buffer> GetTransferBuffer(int32 id) OVERRIDE;
 
  private:
   virtual ~TransferBufferManager();
 
   typedef base::hash_map<int32, scoped_refptr<Buffer> > BufferMap;
   BufferMap registered_buffers_;
   size_t shared_memory_bytes_allocated_;
 
   DISALLOW_COPY_AND_ASSIGN(TransferBufferManager);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_TRANSFER_BUFFER_MANAGER_H_