onCancel = function() {
    component.dispose();
    // On cancel, return to widget start page.
    firebaseui.auth.widget.handler.common.handleSignInStart(app, container);
  }
Handles password recovery.

@param {firebaseui.auth.AuthUI} app The current FirebaseUI instance whose
    configuration is used.
@param {Element} container The container DOM element.
@param {string=} opt_email The email address of the account.
@param {boolean=} opt_disableCancel Whether to disable the cancel link.
@param {string=} opt_infoBarMessage The message to show on info bar.