gpu: Directly cast ClientBuffer to gfx::GpuMemoryBuffer

gpu/command_buffer/client/gpu_memory_buffer_manager.h

 // Copyright 2014 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_CLIENT_GPU_MEMORY_BUFFER_MANAGER_H_
 #define GPU_COMMAND_BUFFER_CLIENT_GPU_MEMORY_BUFFER_MANAGER_H_
 
 #include <memory>
 
 #include "gpu/gpu_export.h"
@@ skipping 15 matching lines @@
       gfx::BufferFormat format,
       gfx::BufferUsage usage,
       gpu::SurfaceHandle surface_handle) = 0;
 
   // Creates a GpuMemoryBuffer from existing handle.
   virtual std::unique_ptr<gfx::GpuMemoryBuffer> CreateGpuMemoryBufferFromHandle(
       const gfx::GpuMemoryBufferHandle& handle,
       const gfx::Size& size,
       gfx::BufferFormat format) = 0;
 
-  // Returns a GpuMemoryBuffer instance given a ClientBuffer. Returns NULL on
-  // failure.
-  virtual gfx::GpuMemoryBuffer* GpuMemoryBufferFromClientBuffer(
-      ClientBuffer buffer) = 0;
-
   // Associates destruction sync point with |buffer|.
   virtual void SetDestructionSyncToken(gfx::GpuMemoryBuffer* buffer,
                                        const gpu::SyncToken& sync_token) = 0;
 
  protected:
   virtual ~GpuMemoryBufferManager();
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GPU_MEMORY_BUFFER_MANAGER_H_