Replace more ObserverList with base::ObserverList.

sync/test/fake_server/fake_server.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 SYNC_TEST_FAKE_SERVER_FAKE_SERVER_H_
 #define SYNC_TEST_FAKE_SERVER_FAKE_SERVER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 188 matching lines @@
   // |error_type_| or |triggered_actionable_error_|) on every other request.
   // |alternate_triggered_errors_| is set if this feature is enabled and
   // |request_counter_| is used to send triggered errors on odd-numbered
   // requests. Note that |request_counter_| can be reset and is not necessarily
   // indicative of the total number of requests handled during the object's
   // lifetime.
   bool alternate_triggered_errors_;
   int request_counter_;
 
   // FakeServer's observers.
-  ObserverList<Observer, true> observers_;
+  base::ObserverList<Observer, true> observers_;
 
   // When true, the server operates normally. When false, a failure is returned
   // on every request. This is used to simulate a network failure on the client.
   bool network_enabled_;
 };
 
 }  // namespace fake_server
 
 #endif  // SYNC_TEST_FAKE_SERVER_FAKE_SERVER_H_