Remove #pragma once from ash

ash/screen_ash.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_SCREEN_ASH_H_
 #define ASH_SCREEN_ASH_H_
-#pragma once
 
 #include "ash/ash_export.h"
 #include "base/compiler_specific.h"
 #include "ui/gfx/insets.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/screen_impl.h"
 
 namespace ash {
 
 // Aura implementation of gfx::Screen. Implemented here to avoid circular
@@ skipping 23 matching lines @@
       const gfx::Rect& match_rect) const OVERRIDE;
   virtual gfx::Display GetPrimaryDisplay() const OVERRIDE;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ScreenAsh);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SCREEN_ASH_H_