Standardize usage of virtual/override/final in content/browser/

content/browser/time_zone_monitor_mac.mm

 // 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.
 
 #include "content/browser/time_zone_monitor.h"
 
 #import <Foundation/Foundation.h>
 
 namespace content {
 
 class TimeZoneMonitorMac : public TimeZoneMonitor {
  public:
   TimeZoneMonitorMac() : TimeZoneMonitor() {
     NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
     notification_observer_ =
         [nc addObserverForName:NSSystemTimeZoneDidChangeNotification
                         object:nil
                          queue:nil
                     usingBlock:^(NSNotification* notification) {
                         NotifyRenderers();
                     }];
   }
 
-  virtual ~TimeZoneMonitorMac() {
+  ~TimeZoneMonitorMac() override {
     NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
     [nc removeObserver:notification_observer_];
   }
 
  private:
   id notification_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(TimeZoneMonitorMac);
 };
 
 // static
 scoped_ptr<TimeZoneMonitor> TimeZoneMonitor::Create() {
   return scoped_ptr<TimeZoneMonitor>(new TimeZoneMonitorMac());
 }
 
 }  // namespace content