content: Cleanup class/struct forward declarations

content/renderer/child_frame_compositing_helper.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 CONTENT_RENDERER_CHILD_FRAME_COMPOSITING_HELPER_H_
 #define CONTENT_RENDERER_CHILD_FRAME_COMPOSITING_HELPER_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/shared_memory.h"
 #include "base/memory/weak_ptr.h"
 #include "cc/surfaces/surface_id.h"
 #include "content/common/content_export.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace cc {
 struct SurfaceSequence;
 
-class CompositorFrame;
 class Layer;
 }
 
 namespace blink {
 class WebLayer;
 class WebPluginContainer;
 class WebRemoteFrame;
 }
 
 namespace gfx {
@@ skipping 75 matching lines @@
   std::unique_ptr<blink::WebLayer> web_layer_;
   cc::SurfaceId surface_id_;
   blink::WebRemoteFrame* frame_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildFrameCompositingHelper);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_CHILD_FRAME_COMPOSITING_HELPER_H_