services: Cleanup class/struct fwd declarations

services/ui/ws/gpu_service_proxy_delegate.h

 // Copyright 2016 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 SERVICES_UI_WS_GPU_SERVICE_PROXY_DELEGATEH_
 #define SERVICES_UI_WS_GPU_SERVICE_PROXY_DELEGATEH_
 
 #include "base/memory/ref_counted.h"
 
-namespace gpu {
-class GpuChannelHost;
-}
-
 namespace ui {
 namespace ws {
 
 class GpuServiceProxyDelegate {
  public:
   virtual ~GpuServiceProxyDelegate() {}
 
   virtual void OnGpuServiceInitialized() = 0;
 };
 
 }  // namespace ws
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_GPU_SERVICE_PROXY_DELEGATEH_