Standardize usage of virtual/override/final in extensions/

extensions/common/manifest_handlers/icons_handler.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 EXTENSIONS_COMMON_MANIFEST_HANDLERS_ICONS_HANDLER_H_
 #define EXTENSIONS_COMMON_MANIFEST_HANDLERS_ICONS_HANDLER_H_
 
 #include <string>
 
 #include "extensions/common/extension.h"
@@ skipping 19 matching lines @@
       ExtensionIconSet::MatchType match_type);
   static GURL GetIconURL(const Extension* extension,
                          int size,
                          ExtensionIconSet::MatchType match_type);
 };
 
 // Parses the "icons" manifest key.
 class IconsHandler : public ManifestHandler {
  public:
   IconsHandler();
-  virtual ~IconsHandler();
+  ~IconsHandler() override;
 
-  virtual bool Parse(Extension* extension, base::string16* error) override;
-  virtual bool Validate(const Extension* extension,
-                        std::string* error,
-                        std::vector<InstallWarning>* warnings) const override;
+  bool Parse(Extension* extension, base::string16* error) override;
+  bool Validate(const Extension* extension,
+                std::string* error,
+                std::vector<InstallWarning>* warnings) const override;
 
  private:
-  virtual const std::vector<std::string> Keys() const override;
+  const std::vector<std::string> Keys() const override;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_MANIFEST_HANDLERS_ICONS_HANDLER_H_