Remove #pragma once from content

content/public/browser/notification_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 CONTENT_PUBLIC_BROWSER_NOTIFICATION_OBSERVER_H_
 #define CONTENT_PUBLIC_BROWSER_NOTIFICATION_OBSERVER_H_
-#pragma once
 
 #include "content/common/content_export.h"
 
 namespace content {
 
 class NotificationDetails;
 class NotificationSource;
 
 // This is the base class for notification observers. When a matching
 // notification is posted to the notification service, Observe is called.
 class CONTENT_EXPORT NotificationObserver {
  public:
   virtual void Observe(int type,
                        const NotificationSource& source,
                        const NotificationDetails& details) = 0;
 
  protected:
   virtual ~NotificationObserver() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_NOTIFICATION_OBSERVER_H_