Mojo: Convert OVERRIDE -> override in various subdirectories of mojo/.

mojo/shell/app_child_process.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 MOJO_SHELL_APP_CHILD_PROCESS_H_
 #define MOJO_SHELL_APP_CHILD_PROCESS_H_
 
 #include "base/macros.h"
 #include "mojo/shell/child_process.h"
 
 namespace mojo {
 namespace shell {
 
 // An implementation of |ChildProcess| for a |TYPE_APP| child process, which
 // runs a single app (loaded from the file system) on its main thread.
 class AppChildProcess : public ChildProcess {
  public:
   AppChildProcess();
   virtual ~AppChildProcess();
 
-  virtual void Main() OVERRIDE;
+  virtual void Main() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AppChildProcess);
 };
 
 }  // namespace shell
 }  // namespace mojo
 
 #endif  // MOJO_SHELL_APP_CHILD_PROCESS_H_