Update {virtual,override,final} to follow C++11 style in ash.

ash/system/chromeos/screen_security/screen_capture_tray_item.h

Index: ash/system/chromeos/screen_security/screen_capture_tray_item.h
diff --git a/ash/system/chromeos/screen_security/screen_capture_tray_item.h b/ash/system/chromeos/screen_security/screen_capture_tray_item.h
index 8143464a328a50ebdc15c14ead54e4292dabb8bb..5c6ed8aeac9141b1e992bb9e4064453d7b1374f4 100644
--- a/ash/system/chromeos/screen_security/screen_capture_tray_item.h
+++ b/ash/system/chromeos/screen_security/screen_capture_tray_item.h
@@ -18,22 +18,22 @@ class ASH_EXPORT ScreenCaptureTrayItem : public ScreenTrayItem,
                                          public ScreenCaptureObserver {
  public:
   explicit ScreenCaptureTrayItem(SystemTray* system_tray);
-  virtual ~ScreenCaptureTrayItem();
+  ~ScreenCaptureTrayItem() override;
 
  private:
   // Overridden from SystemTrayItem.
-  virtual views::View* CreateTrayView(user::LoginStatus status) override;
-  virtual views::View* CreateDefaultView(user::LoginStatus status) override;
+  views::View* CreateTrayView(user::LoginStatus status) override;
+  views::View* CreateDefaultView(user::LoginStatus status) override;
 
   // Overridden from ScreenTrayItem.
-  virtual void CreateOrUpdateNotification() override;
-  virtual std::string GetNotificationId() override;
+  void CreateOrUpdateNotification() override;
+  std::string GetNotificationId() override;
 
   // Overridden from ScreenCaptureObserver.
-  virtual void OnScreenCaptureStart(
+  void OnScreenCaptureStart(
       const base::Closure& stop_callback,
       const base::string16& screen_capture_status) override;
-  virtual void OnScreenCaptureStop() override;
+  void OnScreenCaptureStop() override;
 
   base::string16 screen_capture_status_;