arc: Prevent showing Opt-in UI when it is not expected.

chrome/browser/chromeos/arc/arc_auth_service.cc

Index: chrome/browser/chromeos/arc/arc_auth_service.cc
diff --git a/chrome/browser/chromeos/arc/arc_auth_service.cc b/chrome/browser/chromeos/arc/arc_auth_service.cc
index 58f9a48b753f1bd729de483e9859e22e348e6e31..ed8322b5492e76e9447249f769d40035f91dd0ad 100644
--- a/chrome/browser/chromeos/arc/arc_auth_service.cc
+++ b/chrome/browser/chromeos/arc/arc_auth_service.cc
@@ -412,6 +412,7 @@ void ArcAuthService::RemoveObserver(Observer* observer) {
 
 void ArcAuthService::CloseUI() {
   FOR_EACH_OBSERVER(Observer, observer_list_, OnOptInUIClose());
+  SetUIPage(UIPage::NO_PAGE, base::string16());
   if (!disable_ui_for_testing)
     ArcAuthNotification::Hide();
 }