content: Cleanup class/struct forward declarations

content/browser/renderer_host/delegated_frame_host.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_BROWSER_RENDERER_HOST_DELEGATED_FRAME_HOST_H_
 #define CONTENT_BROWSER_RENDERER_HOST_DELEGATED_FRAME_HOST_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 28 matching lines @@
 }
 
 namespace display_compositor {
 class ReadbackYUVInterface;
 }
 
 namespace content {
 
 class DelegatedFrameHost;
 class RenderWidgetHostViewFrameSubscriber;
-class RenderWidgetHostImpl;
 class ResizeLock;
 
 // The DelegatedFrameHostClient is the interface from the DelegatedFrameHost,
 // which manages delegated frames, and the ui::Compositor being used to
 // display them.
 class CONTENT_EXPORT DelegatedFrameHostClient {
  public:
   virtual ui::Layer* DelegatedFrameHostGetLayer() const = 0;
   virtual bool DelegatedFrameHostIsVisible() const = 0;
 
@@ skipping 271 matching lines @@
   // YUV readback pipeline.
   std::unique_ptr<display_compositor::ReadbackYUVInterface>
       yuv_readback_pipeline_;
 
   std::unique_ptr<DelegatedFrameEvictor> delegated_frame_evictor_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_DELEGATED_FRAME_HOST_H_