Replace more ObserverList with base::ObserverList.

ui/app_list/app_list_model.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 UI_APP_LIST_APP_LIST_MODEL_H_
 #define UI_APP_LIST_APP_LIST_MODEL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 202 matching lines @@
   scoped_ptr<AppListItem> RemoveItemFromFolder(AppListFolderItem* folder,
                                                AppListItem* item);
 
   scoped_ptr<AppListItemList> top_level_item_list_;
 
   scoped_ptr<SearchBoxModel> search_box_;
   scoped_ptr<SearchResults> results_;
 
   Status status_;
   State state_;
-  ObserverList<AppListModelObserver, true> observers_;
+  base::ObserverList<AppListModelObserver, true> observers_;
   bool folders_enabled_;
   bool custom_launcher_page_enabled_;
   std::string custom_launcher_page_name_;
   bool search_engine_is_google_;
 
   // The current number of subpages the custom launcher page has pushed.
   int custom_launcher_page_subpage_depth_;
 
   DISALLOW_COPY_AND_ASSIGN(AppListModel);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_APP_LIST_MODEL_H_