Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/ui/app_list/apps_model_builder.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_APP_LIST_APPS_MODEL_BUILDER_H_
 #define CHROME_BROWSER_UI_APP_LIST_APPS_MODEL_BUILDER_H_
 
 #include <string>
 
 #include "base/gtest_prod_util.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ui/app_list/app_list_model.h"
 #include "ui/base/models/list_model_observer.h"
 
 class AppListControllerDelegate;
 class ExtensionAppItem;
 class Profile;
 
 class AppsModelBuilder : public content::NotificationObserver,
+                         public PrefObserver,
                          public ui::ListModelObserver {
  public:
   AppsModelBuilder(Profile* profile,
                    app_list::AppListModel::Apps* model,
                    AppListControllerDelegate* controller);
   virtual ~AppsModelBuilder();
 
   // Populates the model.
   void Build();
 
@@ skipping 17 matching lines @@
   void HighlightApp();
 
   // Returns app instance at given |index|.
   ExtensionAppItem* GetAppAt(size_t index);
 
   // content::NotificationObserver
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // ui::ListModelObserver overrides:
   virtual void ListItemsAdded(size_t start, size_t count) OVERRIDE;
   virtual void ListItemsRemoved(size_t start, size_t count) OVERRIDE;
   virtual void ListItemMoved(size_t index, size_t target_index) OVERRIDE;
   virtual void ListItemsChanged(size_t start, size_t count) OVERRIDE;
 
   Profile* profile_;
   AppListControllerDelegate* controller_;
 
   // Sub apps model of AppListModel that represents apps grid view.
   app_list::AppListModel::Apps* model_;
 
   std::string highlight_app_id_;
 
   // True to ignore |model_| changes.
   bool ignore_changes_;
 
   content::NotificationRegistrar registrar_;
   PrefChangeRegistrar pref_change_registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(AppsModelBuilder);
 };
 
 #endif  // CHROME_BROWSER_UI_APP_LIST_APPS_MODEL_BUILDER_H_