he menu is open.
       *
       * @attribute opened
       * @type boolean
       * @default false
       */
      opened: false

    },

    eventDelegates: {
      'tap': 'toggleOverlay'
    },

    overlayListeners: {
      'core-overlay-open': 'openAction'
    },

    get dropdown() {
      if (!this._dropdown) {
        this._dropdown = this.querySelector('.dropdown');
        for (var l in this.overlayListeners) {
          this.addElementListener(this._dropdown, l, this.overlayListeners[l]);
       