Remove #pragma once from ash

ash/system/tray/system_tray_bubble.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_BUBBLE_H_
 #define ASH_SYSTEM_TRAY_SYSTEM_TRAY_BUBBLE_H_
-#pragma once
 
 #include "ash/system/tray/tray_bubble_view.h"
 #include "ash/system/user/login_status.h"
 #include "ash/wm/shelf_types.h"
 #include "base/base_export.h"
 #include "base/timer.h"
 #include "ui/views/widget/widget.h"
 
 #include <vector>
 
@@ skipping 76 matching lines @@
   int autoclose_delay_;
   base::OneShotTimer<SystemTrayBubble> autoclose_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemTrayBubble);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_BUBBLE_H_