Use PrefChangeRegistrar everywhere

chrome/browser/dom_ui/shown_sections_handler.h

 // Copyright (c) 2010 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_DOM_UI_SHOWN_SECTIONS_HANDLER_H_
 #define CHROME_BROWSER_DOM_UI_SHOWN_SECTIONS_HANDLER_H_
 #pragma once
 
 #include "chrome/browser/dom_ui/dom_ui.h"
 #include "chrome/common/notification_observer.h"
+#include "chrome/browser/prefs/pref_change_registrar.h"
 
 class DOMUI;
 class Value;
 class PrefService;
 
 // Use for the shown sections bitmask.
 // Currently, only the THUMB and APPS sections can be toggled by the user. Other
 // sections are shown automatically if they have data, and hidden otherwise.
 enum Section {
   THUMB = 1,
   APPS = 64
 };
 
 class ShownSectionsHandler : public DOMMessageHandler,
                              public NotificationObserver {
  public:
   explicit ShownSectionsHandler(PrefService* pref_service);
-  virtual ~ShownSectionsHandler();
+  virtual ~ShownSectionsHandler() {}
 
   // Helper to get the current shown sections.
   static int GetShownSections(PrefService* pref_service);
 
   // DOMMessageHandler implementation.
   virtual void RegisterMessages();
 
   // NotificationObserver implementation.
   virtual void Observe(NotificationType type,
                        const NotificationSource& source,
                        const NotificationDetails& details);
 
   // Callback for "getShownSections" message.
   void HandleGetShownSections(const ListValue* args);
 
   // Callback for "setShownSections" message.
   void HandleSetShownSections(const ListValue* args);
 
   static void RegisterUserPrefs(PrefService* pref_service);
 
   static void MigrateUserPrefs(PrefService* pref_service,
                                int old_pref_version,
                                int new_pref_version);
 
  private:
   PrefService* pref_service_;
+  PrefChangeRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(ShownSectionsHandler);
 };
 
 #endif  // CHROME_BROWSER_DOM_UI_SHOWN_SECTIONS_HANDLER_H_