 = event.path ? event.path[0] : event.target;
      if (target.id) {
        this._ariaDescribedBy = this._appendStringWithSpace(this._ariaDescribedBy, target.id);
      } else {
        var id = 'paper-input-add-on-' + Math.floor((Math.random() * 100000));
        target.id = id;
        this._ariaDescribedBy = this._appendStringWithSpace(this._ariaDescribedBy, id);
      }
    },

    /**
     * Validates the input element and sets an error style if needed.
     *
     * @return {boolean}
     */
    vali