Replace more ObserverList with base::ObserverList.

ui/app_list/app_list_item_list.h

 // Copyright (c) 2013 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_ITEM_LIST_H_
 #define UI_APP_LIST_APP_LIST_ITEM_LIST_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 88 matching lines @@
   // Returns the index at which to insert an item in |app_list_items_| based on
   // |position| (which must be valid) and |id| (if the positions are equal).
   size_t GetItemSortOrderIndex(const syncer::StringOrdinal& position,
                                const std::string& id);
 
   // Fixes the position of the item at |index| when the position matches the
   // previous item's position. |index| must be > 0.
   void FixItemPosition(size_t index);
 
   ScopedVector<AppListItem> app_list_items_;
-  ObserverList<AppListItemListObserver, true> observers_;
+  base::ObserverList<AppListItemListObserver, true> observers_;
   std::string highlighted_id_;
 
   DISALLOW_COPY_AND_ASSIGN(AppListItemList);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_APP_LIST_ITEM_LIST_H_