ash: Cleanup class/struct forward declarations

ash/display/shared_display_edge_indicator.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_DISPLAY_SHARED_DISPLAY_EDGE_INDICATOR_H_
 #define ASH_DISPLAY_SHARED_DISPLAY_EDGE_INDICATOR_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
 #include "base/macros.h"
 #include "ui/gfx/animation/animation_delegate.h"
 
 namespace gfx {
 class Rect;
 class ThrobAnimation;
 }
 
 namespace views {
 class View;
-class Widget;
 }
 
 namespace ash {
 
 // SharedDisplayEdgeIndicator is responsible for showing a window that indicates
 // the edge that a window can be dragged into another display.
 class ASH_EXPORT SharedDisplayEdgeIndicator : public gfx::AnimationDelegate {
  public:
   SharedDisplayEdgeIndicator();
   ~SharedDisplayEdgeIndicator() override;
@@ skipping 16 matching lines @@
 
   // Used to transition the opacity.
   std::unique_ptr<gfx::ThrobAnimation> animation_;
 
   DISALLOW_COPY_AND_ASSIGN(SharedDisplayEdgeIndicator);
 };
 
 }  // namespace ash
 
 #endif  // ASH_DISPLAY_SHARED_DISPLAY_EDGE_INDICATOR_H_