gpu: Directly cast ClientBuffer to gfx::GpuMemoryBuffer

cc/test/test_gpu_memory_buffer_manager.cc

 // 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.
 
 #include "cc/test/test_gpu_memory_buffer_manager.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/logging.h"
@@ skipping 171 matching lines @@
 
   last_gpu_memory_buffer_id_ += 1;
   std::unique_ptr<gfx::GpuMemoryBuffer> result(new GpuMemoryBufferImpl(
       this, last_gpu_memory_buffer_id_, size, format,
       base::MakeUnique<base::SharedMemory>(handle.handle, false), handle.offset,
       handle.stride));
   buffers_[last_gpu_memory_buffer_id_] = result.get();
   return result;
 }
 
-gfx::GpuMemoryBuffer*
-TestGpuMemoryBufferManager::GpuMemoryBufferFromClientBuffer(
-    ClientBuffer buffer) {
-  return reinterpret_cast<gfx::GpuMemoryBuffer*>(buffer);
-}
-
 void TestGpuMemoryBufferManager::SetDestructionSyncToken(
     gfx::GpuMemoryBuffer* buffer,
     const gpu::SyncToken& sync_token) {}
 
 }  // namespace cc