ash: Cleanup class/struct forward declarations

ash/common/system/chromeos/power/tray_power.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_COMMON_SYSTEM_CHROMEOS_POWER_TRAY_POWER_H_
 #define ASH_COMMON_SYSTEM_CHROMEOS_POWER_TRAY_POWER_H_
 
 #include <memory>
 
 #include "ash/common/system/chromeos/power/power_status.h"
 #include "ash/common/system/tray/system_tray_item.h"
 #include "base/macros.h"
 
-class SkBitmap;
-
-namespace gfx {
-class Image;
-class ImageSkia;
-}
-
 namespace message_center {
 class MessageCenter;
 }
 
 namespace ash {
 
 class BatteryNotification;
 class DualRoleNotification;
 
 namespace tray {
@@ skipping 84 matching lines @@
   // Has the user already dismissed a low-power notification? Should be set
   // back to false when all power sources are disconnected.
   bool usb_notification_dismissed_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayPower);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_CHROMEOS_POWER_TRAY_POWER_H_