content: Cleanup class/struct forward declarations

content/browser/renderer_host/render_widget_host_impl.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_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 39 matching lines @@
 struct FrameHostMsg_HittestData_Params;
 struct ViewHostMsg_SelectionBounds_Params;
 struct ViewHostMsg_UpdateRect_Params;
 
 namespace base {
 class RefCountedBytes;
 }
 
 namespace blink {
 class WebInputEvent;
-#if defined(OS_ANDROID)
-class WebLayer;
-#endif
 class WebMouseEvent;
 struct WebCompositionUnderline;
 }
 
-namespace cc {
-class CompositorFrameAck;
-}
-
 #if defined(OS_MACOSX)
 namespace device {
 class PowerSaveBlocker;
 }  // namespace device
 #endif
 
 namespace gfx {
 class Range;
 }
 
@@ skipping 781 matching lines @@
 #endif
 
   base::WeakPtrFactory<RenderWidgetHostImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_IMPL_H_