Add device policy to disallow shutdown

ash/metrics/user_metrics_recorder.h

Index: ash/metrics/user_metrics_recorder.h
diff --git a/ash/metrics/user_metrics_recorder.h b/ash/metrics/user_metrics_recorder.h
index 11d274adde7ac2ded4e213f5b155846d3bf4bb7d..06d881fc69eb2b8d50d02792eac86e4a150d5af7 100644
--- a/ash/metrics/user_metrics_recorder.h
+++ b/ash/metrics/user_metrics_recorder.h
@@ -109,6 +109,9 @@ enum UserMetricsAction {
   // Window selection started by beginning an alt+tab cycle. This does not count
   // each step through an alt+tab cycle.
   UMA_WINDOW_CYCLE,
+
+  // Reboot action triggered by the user
+  UMA_ACCEL_RESTART_POWER_BUTTON,
 };
 
 // User Metrics Recorder provides a repeating callback (RecordPeriodicMetrics)