kiosk: Fix OobeScreenWaiter get wrong current screen

chrome/browser/ui/webui/chromeos/login/oobe_ui.cc

 // Copyright (c) 2012 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 "chrome/browser/ui/webui/chromeos/login/oobe_ui.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 582 matching lines @@
                 new_screen) != std::end(kDimOverlayScreenIds);
   if (!chrome::IsRunningInMash()) {
     ash::ScreenDimmer* screen_dimmer = ash::ScreenDimmer::GetForContainer(
         ash::kShellWindowId_LockScreenContainersContainer);
     screen_dimmer->set_at_bottom(true);
     screen_dimmer->SetDimming(should_dim);
   } else {
     NOTIMPLEMENTED();
   }
 
+  current_screen_ = new_screen;
   FOR_EACH_OBSERVER(Observer,
                     observer_list_,
                     OnCurrentScreenChanged(current_screen_, new_screen));
-  current_screen_ = new_screen;
 }
 
 }  // namespace chromeos