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

ash/system/tray/default_system_tray_delegate.cc

Index: ash/system/tray/default_system_tray_delegate.cc
diff --git a/ash/system/tray/default_system_tray_delegate.cc b/ash/system/tray/default_system_tray_delegate.cc
index fda48075ec2a16db115abc50ec9a13f781bd3346..af594ed5e4358805ed87f6eea087da9f1a694418 100644
--- a/ash/system/tray/default_system_tray_delegate.cc
+++ b/ash/system/tray/default_system_tray_delegate.cc
@@ -90,7 +90,11 @@ bool DefaultSystemTrayDelegate::IsUserSupervised() const {
   return false;
 }
 
-bool DefaultSystemTrayDelegate::SystemShouldUpgrade() const {
+bool DefaultSystemTrayDelegate::SystemShouldUpgrade(UpdateInfo* info) const {
+  if (info) {
+    info->severity = UpdateInfo::UPDATE_NORMAL;
+    info->is_factory_reset_required = false;
+  }
   return true;
 }