ash: Cleanup class/struct forward declarations

ash/test/mirror_window_test_api.h

 // Copyright (c) 2013 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_TEST_MIRROR_WINDOW_TEST_API_H_
 #define ASH_TEST_MIRROR_WINDOW_TEST_API_H_
 
 #include "base/macros.h"
 
 namespace aura {
 class Window;
 class WindowTreeHost;
 }
 
 namespace gfx {
 class Point;
 }
 
 namespace ash {
-class RootWindowTransformer;
 
 namespace test {
 
 class MirrorWindowTestApi {
  public:
   MirrorWindowTestApi() {}
   ~MirrorWindowTestApi() {}
 
   const aura::WindowTreeHost* GetHost() const;
 
@@ skipping 11 matching lines @@
   gfx::Point GetCursorLocation() const;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MirrorWindowTestApi);
 };
 
 }  // namespace test
 }  // namespace ash
 
 #endif  // ASH_TEST_MIRROR_WINDOW_TEST_API_H_