Remove #pragma once from chrome/browser/extensions

chrome/browser/extensions/settings/settings_observer.h

 // Copyright (c) 2011 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 CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_OBSERVER_H_
 #define CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_OBSERVER_H_
-#pragma once
 
 #include "base/observer_list_threadsafe.h"
 #include "chrome/browser/extensions/settings/settings_namespace.h"
 
 namespace extensions {
 
 // Interface for classes that listen to changes to extension settings.
 class SettingsObserver {
  public:
   // Called when a list of settings have changed for an extension.
   virtual void OnSettingsChanged(
       const std::string& extension_id,
       settings_namespace::Namespace settings_namespace,
       const std::string& changes_json) = 0;
 
   virtual ~SettingsObserver() {}
 };
 
 typedef ObserverListThreadSafe<SettingsObserver>
     SettingsObserverList;
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_OBSERVER_H_