ash: Cleanup class/struct forward declarations

ash/wm/resize_shadow.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 ASH_WM_RESIZE_SHADOW_H_
 #define ASH_WM_RESIZE_SHADOW_H_
 
 #include <memory>
 
 #include "base/macros.h"
 
 namespace aura {
 class Window;
 }
 namespace gfx {
 class Rect;
 }
-namespace ui {
-class Layer;
-}
 namespace wm {
 class ImageGrid;
 }
 
 namespace ash {
 
 // A class to render the resize edge effect when the user moves their mouse
 // over a sizing edge.  This is just a visual effect; the actual resize is
 // handled by the EventFilter.
 class ResizeShadow {
@@ skipping 23 matching lines @@
   // Hit test value from last call to ShowForHitTest().  Used to prevent
   // repeatedly triggering the same animations for the same hit.
   int last_hit_test_;
 
   DISALLOW_COPY_AND_ASSIGN(ResizeShadow);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_RESIZE_SHADOW_H_