constructor(onDismissClick, opt_domHelper) {
    super(
        firebaseui.auth.soy2.page.anonymousUserMismatch, undefined,
        opt_domHelper, 'anonymousUserMismatch');
    this.onDismissClick_ = onDismissClick;
  }
@param {function()} onDismissClick Callback to invoke when dismiss button
    is clicked.
@param {?goog.dom.DomHelper=} opt_domHelper Optional DOM helper.