Standardize usage of virtual/override/final in extensions/

extensions/common/manifest_handlers/oauth2_manifest_handler.h

 // Copyright (c) 2013 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_OAUTH2_MANIFEST_HANDLER_H_
 #define EXTENSIONS_COMMON_MANIFEST_HANDLERS_OAUTH2_MANIFEST_HANDLER_H_
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_handler.h"
 
 namespace extensions {
 
 // OAuth2 info included in the extension.
 struct OAuth2Info : public Extension::ManifestData {
   OAuth2Info();
-  virtual ~OAuth2Info();
+  ~OAuth2Info() override;
 
   std::string client_id;
   std::vector<std::string> scopes;
 
   // Indicates that approval UI can be skipped for a set of whitelisted apps.
   bool auto_approve;
 
   static const OAuth2Info& GetOAuth2Info(const Extension* extension);
 };
 
 // Parses the "oauth2" manifest key.
 class OAuth2ManifestHandler : public ManifestHandler {
  public:
   OAuth2ManifestHandler();
-  virtual ~OAuth2ManifestHandler();
+  ~OAuth2ManifestHandler() override;
 
-  virtual bool Parse(Extension* extension,
-                     base::string16* error) override;
+  bool Parse(Extension* extension, base::string16* error) override;
 
  private:
-  virtual const std::vector<std::string> Keys() const override;
+  const std::vector<std::string> Keys() const override;
 
   DISALLOW_COPY_AND_ASSIGN(OAuth2ManifestHandler);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_MANIFEST_HANDLERS_OAUTH2_MANIFEST_HANDLER_H_