other
        // behaviors can override this.
        type: Object
      },

      /**
       * Set to true to enable restoring of focus when overlay is closed.
       */
      restoreFocusOnClose: {
        type: Boolean,
        value: false
      },

      /**
       * Set to true to keep overlay always on top.
       */
      alwaysOnTop: {
        type: Boolean
      },

      /**
       * Shortcut to access to the overlay manager.
       * @private
       * @type {Polymer.IronOverlayManagerClass}
    