   */
      _manager: {
        type: Object,
        value: Polymer.IronOverlayManager
      },

      /**
       * The node being focused.
       * @type {?Node}
       */
      _focusedChild: {
        type: Object
      }

    },

    listeners: {
      'iron-resize': '_onIronResize'
    },

    /**
     * The backdrop element.
     * @type {Element}
     */
    get backdropElement() {
      return this._manager.backdropElement;
    },

    /**
     * Returns the node to give focus to.
     * @type {Nod