vent iron-form-error
     */
    listeners: {
      'iron-form-element-register': '_registerElement',
      'iron-form-element-unregister': '_unregisterElement',
      'submit': '_onSubmit',
      'reset': '_onReset'
    },

    registered: function() {
      // Dear reader: I apologize for what you're about to experience. You see,
      // Safari does not respect `required` on input elements, so it never
      // has any browser validation bubbles to show. And we have to feature
      // detect that, since