Add user action for changing the active window in Ash overview mode

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 328333ec53e3bab8793e6dc9d9e59abbdb110058..8aab4ff31a4557662f5dcbcf3f681aa8ad680186 100644
--- a/ash/metrics/user_metrics_recorder.cc
+++ b/ash/metrics/user_metrics_recorder.cc
@@ -577,6 +577,10 @@ void UserMetricsRecorder::RecordUserMetricsAction(UserMetricsAction action) {
       base::RecordAction(
           base::UserMetricsAction("WindowSelector_Overview"));
       break;
+    case ash::UMA_WINDOW_OVERVIEW_ACTIVE_WINDOW_CHANGED:
+      base::RecordAction(
+          base::UserMetricsAction("WindowSelector_ActiveWindowChanged"));
+      break;
     case ash::UMA_WINDOW_OVERVIEW_ENTER_KEY:
       base::RecordAction(
           base::UserMetricsAction("WindowSelector_OverviewEnterKey"));