Added UMA metrics for the system update UI in the status area.

ash/metrics/user_metrics_recorder.cc

Index: ash/metrics/user_metrics_recorder.cc
diff --git a/ash/metrics/user_metrics_recorder.cc b/ash/metrics/user_metrics_recorder.cc
index 137199a08e16c2fc12c938a58620d7122d4706ed..648b25177223ef98e5afb998644c3205288a255f 100644
--- a/ash/metrics/user_metrics_recorder.cc
+++ b/ash/metrics/user_metrics_recorder.cc
@@ -503,6 +503,10 @@ void UserMetricsRecorder::RecordUserMetricsAction(UserMetricsAction action) {
     case UMA_STATUS_AREA_SIGN_OUT:
       base::RecordAction(base::UserMetricsAction("StatusArea_SignOut"));
       break;
+    case UMA_STATUS_AREA_UPDATE_DEFAULT_SELECTED:
+      base::RecordAction(
+          base::UserMetricsAction("StatusArea_Update_Default_Selected"));
+      break;
     case UMA_STATUS_AREA_VPN_ADD_BUILT_IN_CLICKED:
       base::RecordAction(base::UserMetricsAction("StatusArea_VPN_AddBuiltIn"));
       break;