gpu: Directly cast ClientBuffer to gfx::GpuMemoryBuffer

gpu/ipc/client/gpu_memory_buffer_impl.h

 // Copyright 2013 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_IPC_CLIENT_GPU_MEMORY_BUFFER_IMPL_H_
 #define GPU_IPC_CLIENT_GPU_MEMORY_BUFFER_IMPL_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 16 matching lines @@
   // should match what was used to allocate the |handle|. |callback| is
   // called when instance is deleted, which is not necessarily on the same
   // thread as this function was called on and instance was created on.
   static std::unique_ptr<GpuMemoryBufferImpl> CreateFromHandle(
       const gfx::GpuMemoryBufferHandle& handle,
       const gfx::Size& size,
       gfx::BufferFormat format,
       gfx::BufferUsage usage,
       const DestructionCallback& callback);
 
-  // Type-checking upcast routine. Returns an NULL on failure.
-  static GpuMemoryBufferImpl* FromClientBuffer(ClientBuffer buffer);
-
   // Overridden from gfx::GpuMemoryBuffer:
   gfx::Size GetSize() const override;
   gfx::BufferFormat GetFormat() const override;
   gfx::GpuMemoryBufferId GetId() const override;
   ClientBuffer AsClientBuffer() override;
 
   void set_destruction_sync_token(const gpu::SyncToken& sync_token) {
     destruction_sync_token_ = sync_token;
   }
 
@@ skipping 10 matching lines @@
   bool mapped_;
   gpu::SyncToken destruction_sync_token_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(GpuMemoryBufferImpl);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_IPC_CLIENT_GPU_MEMORY_BUFFER_IMPL_H_