ash: Cleanup class/struct forward declarations

ash/system/chromeos/rotation/tray_rotation_lock.h

 // Copyright 2014 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_SYSTEM_CHROMEOS_ROTATION_TRAY_ROTATION_LOCK_H_
 #define ASH_SYSTEM_CHROMEOS_ROTATION_TRAY_ROTATION_LOCK_H_
 
 #include "ash/common/shell_observer.h"
 #include "ash/common/system/tray/tray_image_item.h"
 #include "ash/display/screen_orientation_controller_chromeos.h"
 #include "base/macros.h"
 
 namespace ash {
 
-namespace tray {
-class RotationLockDefaultView;
-}  // namespace tray
-
 // TrayRotationLock is a provider of views for the SystemTray. Both a tray view
 // and a default view are provided. Each view indicates the current state of
 // the rotation lock for the display which it appears on. The default view can
 // be interacted with, it toggles the state of the rotation lock.
 // TrayRotationLock is only available on the primary display.
 class ASH_EXPORT TrayRotationLock
     : public TrayImageItem,
       public ScreenOrientationController::Observer,
       public ShellObserver {
  public:
@@ skipping 39 matching lines @@
 
   // True while added as a ShellObserver.
   bool observing_shell_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayRotationLock);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_ROTATION_TRAY_ROTATION_LOCK_H_