replace 'virtual ... OVERRIDE' with '... override'

base/time/default_clock.h

 // Copyright (c) 2012 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 BASE_DEFAULT_CLOCK_H_
 #define BASE_DEFAULT_CLOCK_H_
 
 #include "base/base_export.h"
 #include "base/compiler_specific.h"
 #include "base/time/clock.h"
 
 namespace base {
 
 // DefaultClock is a Clock implementation that uses Time::Now().
 class BASE_EXPORT DefaultClock : public Clock {
  public:
   virtual ~DefaultClock();
 
   // Simply returns Time::Now().
-  virtual Time Now() OVERRIDE;
+  Time Now() override;
 };
 
 }  // namespace base
 
 #endif  // BASE_DEFAULT_CLOCK_H_