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

ash/system/chromeos/session/tray_session_length_limit_unittest.cc

 // 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.
 
 #include "ash/system/chromeos/session/tray_session_length_limit.h"
 
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray.h"
 #include "ash/test/ash_test_base.h"
 #include "ash/test/test_system_tray_delegate.h"
 #include "base/time/time.h"
 #include "ui/message_center/message_center.h"
 #include "ui/message_center/notification.h"
 #include "ui/message_center/notification_types.h"
 
 namespace ash {
 namespace test {
 
 class TraySessionLengthLimitTest : public AshTestBase {
  public:
   TraySessionLengthLimitTest() {}
-  virtual ~TraySessionLengthLimitTest() {}
+  ~TraySessionLengthLimitTest() override {}
 
-  virtual void SetUp() override {
+  void SetUp() override {
     AshTestBase::SetUp();
     SystemTray* system_tray =
         Shell::GetPrimaryRootWindowController()->GetSystemTray();
     tray_session_length_limit_ = new TraySessionLengthLimit(system_tray);
     system_tray->AddTrayItem(tray_session_length_limit_);
   }
 
-  virtual void TearDown() override {
-    AshTestBase::TearDown();
-  }
+  void TearDown() override { AshTestBase::TearDown(); }
 
  protected:
   void UpdateSessionLengthLimitInMin(int mins) {
     GetSystemTrayDelegate()->SetSessionLengthLimitForTest(
         base::TimeDelta::FromMinutes(mins));
     tray_session_length_limit_->OnSessionLengthLimitChanged();
   }
 
   message_center::Notification* GetNotification() {
     const message_center::NotificationList::Notifications& notifications =
@@ skipping 104 matching lines @@
   // re-appear and be re-read.
   UpdateSessionLengthLimitInMin(15);
   notification = GetNotification();
   EXPECT_TRUE(notification);
   EXPECT_TRUE(notification->rich_notification_data().
               should_make_spoken_feedback_for_popup_updates);
 }
 
 }  // namespace test
 }  // namespace ash