Standardize usage of virtual/override/final in extensions/

extensions/common/manifest_handlers/file_handler_info.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_FILE_HANDLER_INFO_H_
 #define EXTENSIONS_COMMON_MANIFEST_HANDLERS_FILE_HANDLER_INFO_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 14 matching lines @@
   std::set<std::string> extensions;
 
   // MIME types associated with this handler.
   std::set<std::string> types;
 };
 
 typedef std::vector<FileHandlerInfo> FileHandlersInfo;
 
 struct FileHandlers : public Extension::ManifestData {
   FileHandlers();
-  virtual ~FileHandlers();
+  ~FileHandlers() override;
 
   FileHandlersInfo file_handlers;
 
   static const FileHandlersInfo* GetFileHandlers(const Extension* extension);
 };
 
 // Parses the "file_handlers" manifest key.
 class FileHandlersParser : public ManifestHandler {
  public:
   FileHandlersParser();
-  virtual ~FileHandlersParser();
+  ~FileHandlersParser() 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(FileHandlersParser);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_MANIFEST_HANDLERS_FILE_HANDLER_INFO_H_