Add OVERRIDE to chrome/common/ and nacl/.

chrome/nacl/nacl_listener.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 CHROME_NACL_NACL_LISTENER_H_
 #define CHROME_NACL_NACL_LISTENER_H_
 #pragma once
 
 #include <vector>
 
 #include "chrome/common/nacl_types.h"
 #include "ipc/ipc_channel.h"
 
 // The NaClListener is an IPC channel listener that waits for a
 // request to start a NaCl module.
 class NaClListener : public IPC::Channel::Listener {
  public:
   NaClListener();
   virtual ~NaClListener();
   // Listen for a request to launch a NaCl module.
   void Listen();
   void set_debug_enabled(bool value) {debug_enabled_ = value;}
 
  private:
   void OnStartSelLdr(std::vector<nacl::FileDescriptor> handles);
-  virtual bool OnMessageReceived(const IPC::Message& msg);
+  virtual bool OnMessageReceived(const IPC::Message& msg) OVERRIDE;
 
   bool debug_enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(NaClListener);
 };
 
 #endif  // CHROME_NACL_NACL_LISTENER_H_