Remove #pragma once from ash

ash/system/tray/system_tray.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_SYSTEM_TRAY_H_
 #define ASH_SYSTEM_TRAY_SYSTEM_TRAY_H_
-#pragma once
 
 #include "ash/ash_export.h"
 #include "ash/system/power/power_supply_status.h"
 #include "ash/system/tray/tray_background_view.h"
 #include "ash/system/tray/tray_views.h"
 #include "ash/system/user/login_status.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
@@ skipping 237 matching lines @@
   // Set to true when system notifications should be hidden (e.g. web
   // notification bubble is visible).
   bool hide_notifications_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemTray);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_H_