withCredentials;
      this.request.headers = this.headers;

      if (this.method.toUpperCase() === 'POST') {
        this.request.body = json;
      } else {
        this.request.params = json;
      }

      // Allow for a presubmit hook
      var event = this.fire('iron-form-presubmit', {}, {cancelable: true});
      if(!event.defaultPrevented) {
        this.request.generateRequest();
        this.fire('iron-form-submit', json);
      }
    },

    /**
     * Handler that is called when the native form