C++11 override style change for athena

athena/main/athena_renderer_pdf_helper.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 ATHENA_MAIN_ATHENA_RENDERER_PDF_HELPER_H_
 #define ATHENA_MAIN_ATHENA_RENDERER_PDF_HELPER_H_
 
 #include "content/public/renderer/render_frame_observer.h"
 
 namespace athena {
 
 class AthenaRendererPDFHelper : public content::RenderFrameObserver {
  public:
   explicit AthenaRendererPDFHelper(content::RenderFrame* frame);
-  virtual ~AthenaRendererPDFHelper();
+  ~AthenaRendererPDFHelper() override;
 
  private:
   // RenderFrameObserver:
   virtual void DidCreatePepperPlugin(
       content::RendererPpapiHost* host) override;
 
   DISALLOW_COPY_AND_ASSIGN(AthenaRendererPDFHelper);
 };
 
 }  // namespace athena
 
 #endif  // ATHENA_MAIN_ATHENA_RENDERER_PDF_HELPER_H_