Standardize usage of virtual/override/final in extensions/

extensions/renderer/static_v8_external_one_byte_string_resource.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_RENDERER_STATIC_V8_EXTERNAL_ONE_BYTE_STRING_RESOURCE_H_
 #define EXTENSIONS_RENDERER_STATIC_V8_EXTERNAL_ONE_BYTE_STRING_RESOURCE_H_
 
 #include "base/compiler_specific.h"
 #include "base/strings/string_piece.h"
 #include "v8/include/v8.h"
 
 namespace extensions {
 
 // A very simple implementation of v8::ExternalAsciiStringResource that just
 // wraps a buffer. The buffer must outlive the v8 runtime instance this resource
 // is used in.
 class StaticV8ExternalOneByteStringResource
     : public v8::String::ExternalOneByteStringResource {
  public:
   explicit StaticV8ExternalOneByteStringResource(
       const base::StringPiece& buffer);
-  virtual ~StaticV8ExternalOneByteStringResource();
+  ~StaticV8ExternalOneByteStringResource() override;
 
-  virtual const char* data() const override;
-  virtual size_t length() const override;
+  const char* data() const override;
+  size_t length() const override;
 
  private:
   base::StringPiece buffer_;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_STATIC_V8_EXTERNAL_ONE_BYTE_STRING_RESOURCE_H_