gpu: Cleanup class/struct forward declarations

gpu/command_buffer/client/gpu_control.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_CONTROL_H_
 #define GPU_COMMAND_BUFFER_CLIENT_GPU_CONTROL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <vector>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "gpu/command_buffer/common/capabilities.h"
 #include "gpu/command_buffer/common/command_buffer_id.h"
 #include "gpu/command_buffer/common/constants.h"
 #include "gpu/command_buffer/common/mailbox.h"
 #include "gpu/gpu_export.h"
 
 extern "C" typedef struct _ClientBuffer* ClientBuffer;
 
 namespace base {
 class Lock;
 }
 
-namespace gfx {
-class GpuMemoryBuffer;
-}
-
 namespace gpu {
 class GpuControlClient;
 struct SyncToken;
 
 // Common interface for GpuControl implementations.
 class GPU_EXPORT GpuControl {
  public:
   GpuControl() {}
   virtual ~GpuControl() {}
 
@@ skipping 67 matching lines @@
   // be enqueued first so does not need to be flushed.
   virtual bool CanWaitUnverifiedSyncToken(const SyncToken* sync_token) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(GpuControl);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GPU_CONTROL_H_