content: Cleanup class/struct forward declarations

content/renderer/gpu/renderer_compositor_frame_sink.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.
 
 #ifndef CONTENT_RENDERER_GPU_RENDERER_COMPOSITOR_FRAME_SINK_H_
 #define CONTENT_RENDERER_GPU_RENDERER_COMPOSITOR_FRAME_SINK_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 12 matching lines @@
 #include "content/renderer/gpu/compositor_forwarding_message_filter.h"
 #include "ipc/ipc_sync_message_filter.h"
 
 namespace IPC {
 class Message;
 }
 
 namespace cc {
 class BeginFrameSource;
 class CompositorFrame;
-class CompositorFrameAck;
 class ContextProvider;
 }
 
 namespace content {
 class FrameSwapMessageQueue;
 
 // This class can be created only on the main thread, but then becomes pinned
 // to a fixed thread when BindToClient is called.
 class RendererCompositorFrameSink
     : NON_EXPORTED_BASE(public cc::CompositorFrameSink),
@@ skipping 58 matching lines @@
   scoped_refptr<RendererCompositorFrameSinkProxy> compositor_frame_sink_proxy_;
   scoped_refptr<IPC::SyncMessageFilter> message_sender_;
   scoped_refptr<FrameSwapMessageQueue> frame_swap_message_queue_;
   std::unique_ptr<cc::BeginFrameSource> begin_frame_source_;
   int routing_id_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_GPU_RENDERER_COMPOSITOR_FRAME_SINK_H_