Replace more ObserverList with base::ObserverList.

ipc/ipc_test_sink.h

 // Copyright (c) 2011 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 IPC_IPC_TEST_SINK_H_
 #define IPC_IPC_TEST_SINK_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 110 matching lines @@
   // from OnMessageReceived, subsequent filters will not receive the message
   // and the TestSink will not store it.
   void AddFilter(Listener* filter);
 
   // Removes the given filter from the TestSink.
   void RemoveFilter(Listener* filter);
 
  private:
   // The actual list of received messages.
   std::vector<Message> messages_;
-  ObserverList<Listener> filter_list_;
+  base::ObserverList<Listener> filter_list_;
 
   DISALLOW_COPY_AND_ASSIGN(TestSink);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_TEST_SINK_H_