Remove #pragma once from ash

ash/system/tray/tray_background_view.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_TRAY_BACKGROUND_VIEW_H_
 #define ASH_SYSTEM_TRAY_TRAY_BACKGROUND_VIEW_H_
-#pragma once
 
 #include "ash/ash_export.h"
 #include "ash/launcher/background_animator.h"
 #include "ash/system/tray/tray_views.h"
 #include "ash/wm/shelf_types.h"
 
 namespace ash {
 namespace internal {
 
 class TrayBackground;
@@ skipping 44 matching lines @@
   internal::BackgroundAnimator hide_background_animator_;
   internal::BackgroundAnimator hover_background_animator_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayBackgroundView);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_TRAY_BACKGROUND_VIEW_H_