     } 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);
        }
      },

      _getValidatableElements: function() {
        return this._findElements(this._form, true);
      },

      _getSubmittableElements: function() {
        return this._findElements(t