function announceClosed(opts) {
      var mdSelect = opts.selectCtrl;
      if (mdSelect) {
        var menuController = opts.selectEl.controller('mdSelectMenu');
        mdSelect.setSelectValueText(menuController ? menuController.getSelectedLabels() : '');
        mdSelect.triggerClose();
      }
    }
To notify listeners that the Select menu has closed,
trigger the [optional] user-defined expression