ent) {
      this.fire('iron-form-error', event.detail);
    },

    _registerElement: function(e) {
      // Get the actual element that fired the event
      var element = Polymer.dom(e).rootTarget;

      element._parentForm = this;
      this._customElements.push(element);

      // Save the original value of this input.
      this._customElementsInitialValues.push(
          this._usesCheckedInsteadOfValue(element) ? element.checked : element.value);
    },

    _unregisterElement: function(e) {
      