Remove #pragma once from ash

ash/desktop_background/desktop_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_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_VIEW_H_
 #define ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_VIEW_H_
-#pragma once
 
 #include "ash/desktop_background/desktop_background_resources.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/views/view.h"
 #include "ui/views/widget/widget_delegate.h"
 
 namespace ash {
 namespace internal {
 
 class DesktopBackgroundView : public views::WidgetDelegateView {
  public:
   DesktopBackgroundView();
   virtual ~DesktopBackgroundView();
 
  private:
   // Overridden from views::View:
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
   virtual bool OnMousePressed(const views::MouseEvent& event) OVERRIDE;
   virtual void OnMouseReleased(const views::MouseEvent& event) OVERRIDE;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopBackgroundView);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_VIEW_H_