isDisplayNameRequired() {
    // Get provided sign-in options for specified provider.
    const signInOptions = this.getSignInOptionsForProvider_(
        firebase.auth.EmailAuthProvider.PROVIDER_ID);

    if (signInOptions &&
        typeof signInOptions['requireDisplayName'] !== 'undefined') {
      return /** @type {boolean} */ (!!signInOptions['requireDisplayName']);
    }
    return true;
  }
@return {boolean} Whether the display name should be displayed. Defaults
    to true.