Remove #pragma once from ash

ash/display/multi_display_manager.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_DISPLAY_MULTI_DISPLAY_MANAGER_H_
 #define ASH_DISPLAY_MULTI_DISPLAY_MANAGER_H_
-#pragma once
 
 #include <vector>
 
 #include "ash/ash_export.h"
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "ui/aura/display_manager.h"
 #include "ui/aura/root_window_observer.h"
 #include "ui/aura/window.h"
 
@@ skipping 60 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(MultiDisplayManager);
 };
 
 extern const aura::WindowProperty<int>* const kDisplayIdKey;
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_DISPLAY_MULTI_DISPLAY_MANAGER_H_