Added Aura notification that relaunch and powerwash is required in case of downgrade.

ash/system/tray/system_tray_notifier.cc

Index: ash/system/tray/system_tray_notifier.cc
diff --git a/ash/system/tray/system_tray_notifier.cc b/ash/system/tray/system_tray_notifier.cc
index 1a55f8a1af8731457174bcf5eebbee9922eaba81..cc4bbb03ae177fd3f02c3c745f309a93a5b14367 100644
--- a/ash/system/tray/system_tray_notifier.cc
+++ b/ash/system/tray/system_tray_notifier.cc
@@ -285,11 +285,10 @@ void SystemTrayNotifier::NotifyLocaleChanged(
       OnLocaleChanged(delegate, cur_locale, from_locale, to_locale));
 }
 
-void SystemTrayNotifier::NotifyUpdateRecommended(
-    UpdateObserver::UpdateSeverity severity) {
+void SystemTrayNotifier::NotifyUpdateRecommended(const UpdateInfo& info) {
   FOR_EACH_OBSERVER(UpdateObserver,
                     update_observers_,
-                    OnUpdateRecommended(severity));
+                    OnUpdateRecommended(info));
 }
 
 void SystemTrayNotifier::NotifyUserUpdate() {