Remove #pragma once from ash

ash/system/tray_accessibility.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_ACCESSIBILITY_H_
 #define ASH_SYSTEM_TRAY_ACCESSIBILITY_H_
-#pragma once
 
 #include "ash/system/tray/tray_image_item.h"
 
 namespace views {
 class ImageView;
 class View;
 }
 
 namespace ash {
 
@@ skipping 31 matching lines @@
   views::View* detailed_;
   int string_id_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayAccessibility);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_ACCESSIBILITY_H_