gpu: Cleanup class/struct forward declarations

gpu/command_buffer/client/client_test_helper.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.
 
 // Helper classes for implementing gpu client side unit tests.
 
 #ifndef GPU_COMMAND_BUFFER_CLIENT_CLIENT_TEST_HELPER_H_
 #define GPU_COMMAND_BUFFER_CLIENT_CLIENT_TEST_HELPER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "gpu/command_buffer/client/gpu_control.h"
 #include "gpu/command_buffer/common/cmd_buffer_common.h"
 #include "gpu/command_buffer/common/gpu_memory_allocation.h"
 #include "gpu/command_buffer/common/sync_token.h"
 #include "gpu/command_buffer/service/command_buffer_service.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace gpu {
 
-class CommandBufferHelper;
-
 class MockCommandBufferBase : public CommandBufferServiceBase {
  public:
   static const int32_t kTransferBufferBaseId = 0x123;
   static const int32_t kMaxTransferBuffers = 32;
 
   MockCommandBufferBase();
   ~MockCommandBufferBase() override;
 
   State GetLastState() override;
   int32_t GetLastToken() override;
@@ skipping 87 matching lines @@
   MOCK_METHOD1(CanWaitUnverifiedSyncToken, bool(const SyncToken*));
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MockClientGpuControl);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_CLIENT_TEST_HELPER_H_