@Override
    @CallSuper
    public void onCreate() {
        super.onCreate();
        mNotificationManager =
                (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    }
Called by the system when the service is first created. Do not call this method directly.
Overrides must call {@code super.onCreate()}.
customtabs/src/android/support/customtabs/trusted/TrustedWebActivityService.java