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

ash/system/chromeos/supervised/tray_supervised_user.h

Index: ash/system/chromeos/supervised/tray_supervised_user.h
diff --git a/ash/system/chromeos/supervised/tray_supervised_user.h b/ash/system/chromeos/supervised/tray_supervised_user.h
index 4880d41eaf87461cb12e9fc25780b725f21125ed..3c2b0ce831c02704fd5bc8122d7728cec4da9d4b 100644
--- a/ash/system/chromeos/supervised/tray_supervised_user.h
+++ b/ash/system/chromeos/supervised/tray_supervised_user.h
@@ -20,22 +20,22 @@ class ASH_EXPORT TraySupervisedUser : public SystemTrayItem,
                                       public CustodianInfoTrayObserver {
  public:
   explicit TraySupervisedUser(SystemTray* system_tray);
-  virtual ~TraySupervisedUser();
+  ~TraySupervisedUser() override;
 
   // If message is not empty updates content of default view, otherwise hides
   // tray items.
   void UpdateMessage();
 
   // Overridden from SystemTrayItem.
-  virtual views::View* CreateDefaultView(user::LoginStatus status) override;
-  virtual void DestroyDefaultView() override;
-  virtual void UpdateAfterLoginStatusChange(user::LoginStatus status) override;
+  views::View* CreateDefaultView(user::LoginStatus status) override;
+  void DestroyDefaultView() override;
+  void UpdateAfterLoginStatusChange(user::LoginStatus status) override;
 
   // Overridden from ViewClickListener.
-  virtual void OnViewClicked(views::View* sender) override;
+  void OnViewClicked(views::View* sender) override;
 
   // Overridden from CustodianInfoTrayObserver:
-  virtual void OnCustodianInfoChanged() override;
+  void OnCustodianInfoChanged() override;
 
  private:
   friend class TraySupervisedUserTest;