ash: Cleanup class/struct forward declarations

ash/rotator/window_rotation.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_WINDOW_ROTATION_H_
 #define ASH_WINDOW_ROTATION_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
 #include "base/macros.h"
 #include "ui/compositor/layer_animation_element.h"
 #include "ui/gfx/geometry/point.h"
 
 namespace ui {
 class InterpolatedTransform;
 class Layer;
 }
 
-namespace aura {
-class RootWindow;
-}
-
 namespace ash {
 
 // A window rotation represents a single transition from one window orientation
 // to another. The  intended usage is that a new instance of the class is
 // created for every transition. It is possible to update the target orientation
 // in the middle of a transition.
 class ASH_EXPORT WindowRotation : public ui::LayerAnimationElement {
  public:
   // |degrees| are clockwise. |layer| is the target of the animation. Does not
   // take ownership of |layer|.
@@ skipping 18 matching lines @@
 
   // The target origin.
   gfx::Point new_origin_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowRotation);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WINDOW_ROTATION_H_