Replace more ObserverList with base::ObserverList.

extensions/browser/extension_pref_value_map.h

 // Copyright 2014 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 EXTENSIONS_BROWSER_EXTENSION_PREF_VALUE_MAP_H_
 #define EXTENSIONS_BROWSER_EXTENSION_PREF_VALUE_MAP_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 179 matching lines @@
   // Mapping of which extension set which preference value. The effective
   // preferences values (i.e. the ones with the highest precedence)
   // are stored in ExtensionPrefStores.
   ExtensionEntryMap entries_;
 
   // In normal Profile shutdown, Shutdown() notifies observers that we are
   // being destroyed. In tests, it isn't called, so the notification must
   // be done in the destructor. This bit tracks whether it has been done yet.
   bool destroyed_;
 
-  ObserverList<Observer, true> observers_;
+  base::ObserverList<Observer, true> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionPrefValueMap);
 };
 
 #endif  // EXTENSIONS_BROWSER_EXTENSION_PREF_VALUE_MAP_H_