Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/ui/webui/options/media_galleries_handler.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 CHROME_BROWSER_UI_WEBUI_OPTIONS_MEDIA_GALLERIES_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_OPTIONS_MEDIA_GALLERIES_HANDLER_H_
 
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
 #include "content/public/browser/notification_observer.h"
 #include "ui/base/dialogs/select_file_dialog.h"
 
 namespace options {
 
 // Handles messages related to adding or removing media galleries.
 class MediaGalleriesHandler : public OptionsPageUIHandler,
+                              public PrefObserver,
                               public ui::SelectFileDialog::Listener {
  public:
   MediaGalleriesHandler();
   virtual ~MediaGalleriesHandler();
 
   // OptionsPageUIHandler implementation.
   virtual void GetLocalizedValues(base::DictionaryValue* values) OVERRIDE;
   virtual void InitializePage() OVERRIDE;
   virtual void RegisterMessages() OVERRIDE;
 
   // SelectFileDialog::Listener implementation.
   virtual void FileSelected(const FilePath& path, int index, void* params)
       OVERRIDE;
 
-  // NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   // Handles the "addNewGallery" message (no arguments).
   void HandleAddNewGallery(const base::ListValue* args);
   // Handles "forgetGallery" message. The first and only argument is the id of
   // the gallery.
   void HandleForgetGallery(const base::ListValue* args);
 
   // Called when the list of known galleries has changed; updates the page.
   void OnGalleriesChanged();
 
   PrefChangeRegistrar pref_change_registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaGalleriesHandler);
 };
 
 }  // namespace options
 
 #endif  // CHROME_BROWSER_UI_WEBUI_OPTIONS_MEDIA_GALLERIES_HANDLER_H_