Remove #pragma once from ash

ash/system/network/network_observer.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_NETWORK_NETWORK_OBSERVER_H
 #define ASH_SYSTEM_NETWORK_NETWORK_OBSERVER_H
-#pragma once
 
 #include "base/string16.h"
 
 namespace ash {
 
 struct NetworkIconInfo;
 class NetworkTrayDelegate;
 
 class NetworkTrayDelegate {
  public:
@@ skipping 23 matching lines @@
                                const string16& title,
                                const string16& message,
                                const string16& link_text) = 0;
   // Clears the error notification for |error_type|.
   virtual void ClearNetworkError(ErrorType error_type) = 0;
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_NETWORK_NETWORK_OBSERVER_H