Standardize usage of virtual/override/final in chrome/browser/extensions/

chrome/browser/extensions/api/system_indicator/system_indicator_api.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 CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INDICATOR_SYSTEM_INDICATOR_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INDICATOR_SYSTEM_INDICATOR_API_H_
 
 #include "chrome/browser/extensions/api/extension_action/extension_action_api.h"
 #include "extensions/browser/extension_function.h"
 
 class Profile;
 
 namespace extensions {
 
 class SystemIndicatorSetIconFunction : public ExtensionActionSetIconFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("systemIndicator.setIcon", SYSTEMINDICATOR_SETICON)
 
  protected:
-  virtual ~SystemIndicatorSetIconFunction() {}
+  ~SystemIndicatorSetIconFunction() override {}
 };
 
 class SystemIndicatorEnableFunction : public ExtensionActionShowFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("systemIndicator.enable", SYSTEMINDICATOR_ENABLE)
 
  protected:
-  virtual ~SystemIndicatorEnableFunction() {}
+  ~SystemIndicatorEnableFunction() override {}
 };
 
 class SystemIndicatorDisableFunction : public ExtensionActionHideFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("systemIndicator.disable", SYSTEMINDICATOR_DISABLE)
 
  protected:
-  virtual ~SystemIndicatorDisableFunction() {}
+  ~SystemIndicatorDisableFunction() override {}
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INDICATOR_SYSTEM_INDICATOR_API_H_