Remove #pragma once from ash

ash/system/tray_update.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_SYSTEM_TRAY_UPDATE_H_
 #define ASH_SYSTEM_TRAY_UPDATE_H_
-#pragma once
 
 #include "ash/system/tray/tray_image_item.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace views {
 class View;
 }
 
 namespace ash {
 
@@ skipping 30 matching lines @@
   // unseen update notification.
   scoped_ptr<tray::UpdateNagger> nagger_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayUpdate);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_UPDATE_H_