content: Cleanup class/struct forward declarations

content/browser/web_contents/web_contents_view_aura.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_WEB_CONTENTS_WEB_CONTENTS_VIEW_AURA_H_
 #define CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_AURA_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 13 matching lines @@
 }
 
 namespace ui {
 class DropTargetEvent;
 class TouchSelectionController;
 }
 
 namespace content {
 class GestureNavSimple;
 class OverscrollNavigationOverlay;
-class RenderWidgetHostImpl;
 class RenderWidgetHostViewAura;
-class ShadowLayerDelegate;
 class TouchSelectionControllerClientAura;
 class WebContentsViewDelegate;
 class WebContentsImpl;
 class WebDragDestDelegate;
 
 class CONTENT_EXPORT WebContentsViewAura
     : NON_EXPORTED_BASE(public WebContentsView),
       public RenderViewHostDelegateView,
       public OverscrollControllerDelegate,
       public aura::WindowDelegate,
@@ skipping 166 matching lines @@
   std::unique_ptr<GestureNavSimple> gesture_nav_simple_;
 
   bool init_rwhv_with_null_parent_for_testing_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsViewAura);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_AURA_H_