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

ash/system/chromeos/multi_user/user_switch_util_unittest.cc

Index: ash/system/chromeos/multi_user/user_switch_util_unittest.cc
diff --git a/ash/system/chromeos/multi_user/user_switch_util_unittest.cc b/ash/system/chromeos/multi_user/user_switch_util_unittest.cc
index becf95f42823152310c1fb9b8db739aef1b104d2..adb0bad0fe8b26f37337c8c65afc16a22612df12 100644
--- a/ash/system/chromeos/multi_user/user_switch_util_unittest.cc
+++ b/ash/system/chromeos/multi_user/user_switch_util_unittest.cc
@@ -24,9 +24,9 @@ class TrySwitchingUserTest : public ash::test::AshTestBase {
         stop_capture_callback_hit_count_(0),
         stop_share_callback_hit_count_(0),
         switch_callback_hit_count_(0) {}
-  virtual ~TrySwitchingUserTest() {}
+  ~TrySwitchingUserTest() override {}
 
-  virtual void SetUp() override {
+  void SetUp() override {
     test::AshTestBase::SetUp();
     TrayItemView::DisableAnimationsForTest();
     SystemTray* system_tray =  Shell::GetInstance()->GetPrimarySystemTray();