Update from https://crrev.com/333737

mojo/common/message_pump_mojo.h

 // Copyright 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 MOJO_COMMON_MESSAGE_PUMP_MOJO_H_
 #define MOJO_COMMON_MESSAGE_PUMP_MOJO_H_
 
 #include <map>
 #include <utility>
 #include <vector>
@@ skipping 109 matching lines @@
 
   HandleToHandler handlers_;
 
   // An ever increasing value assigned to each Handler::id. Used to detect
   // uniqueness while notifying. That is, while notifying expired timers we copy
   // |handlers_| and only notify handlers whose id match. If the id does not
   // match it means the handler was removed then added so that we shouldn't
   // notify it.
   int next_handler_id_;
 
-  ObserverList<Observer> observers_;
+  base::ObserverList<Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(MessagePumpMojo);
 };
 
 }  // namespace common
 }  // namespace mojo
 
 #endif  // MOJO_COMMON_MESSAGE_PUMP_MOJO_H_