C++11 override style change for athena

athena/extensions/shell/athena_shell_app_window_client.h

Index: athena/extensions/shell/athena_shell_app_window_client.h
diff --git a/athena/extensions/shell/athena_shell_app_window_client.h b/athena/extensions/shell/athena_shell_app_window_client.h
index 9aac189b6483da8aae3d498db3a442417020cd38..844ed793427e048c358a639f81864cbc05b29de1 100644
--- a/athena/extensions/shell/athena_shell_app_window_client.h
+++ b/athena/extensions/shell/athena_shell_app_window_client.h
@@ -13,16 +13,16 @@ namespace athena {
 class AthenaShellAppWindowClient : public AthenaAppWindowClientBase {
  public:
   AthenaShellAppWindowClient();
-  virtual ~AthenaShellAppWindowClient();
+  ~AthenaShellAppWindowClient() override;
 
  private:
   // extensions::AppWindowClient
-  virtual extensions::AppWindow* CreateAppWindow(
+  extensions::AppWindow* CreateAppWindow(
       content::BrowserContext* context,
       const extensions::Extension* extension) override;
-  virtual void OpenDevToolsWindow(content::WebContents* web_contents,
+  void OpenDevToolsWindow(content::WebContents* web_contents,
                                   const base::Closure& callback) override;
-  virtual bool IsCurrentChannelOlderThanDev() override;
+  bool IsCurrentChannelOlderThanDev() override;
 
   DISALLOW_COPY_AND_ASSIGN(AthenaShellAppWindowClient);
 };