Replace more ObserverList with base::ObserverList.

chromeos/dbus/fake_cras_audio_client.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 CHROMEOS_DBUS_FAKE_CRAS_AUDIO_CLIENT_H_
 #define CHROMEOS_DBUS_FAKE_CRAS_AUDIO_CLIENT_H_
 
 #include "chromeos/chromeos_export.h"
 #include "chromeos/dbus/cras_audio_client.h"
 
@@ skipping 32 matching lines @@
 
   // Calls SetAudioNodesForTesting() and additionally notifies |observers_|.
   void SetAudioNodesAndNotifyObserversForTesting(
       const AudioNodeList& new_nodes);
 
  private:
   VolumeState volume_state_;
   AudioNodeList node_list_;
   uint64 active_input_node_id_;
   uint64 active_output_node_id_;
-  ObserverList<Observer> observers_;
+  base::ObserverList<Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeCrasAudioClient);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_FAKE_CRAS_AUDIO_CLIENT_H_