getEmailLinkSignInActionCodeSettings() {
    if (this.isEmailLinkSignInAllowed()) {
      const actionCodeSettings = {
        'url': util.getCurrentUrl(),
        'handleCodeInApp': true,
      };
      // Get provided sign-in options for specified provider.
      const signInOptions = this.getSignInOptionsForProvider_(
          firebase.auth.EmailAuthProvider.PROVIDER_ID);
      if (signInOptions &&
          typeof signInOptions['emailLinkSignIn'] === 'function') {
        googObject.extend(
            actionCodeSettings,
            signInOptions['emailLinkSignIn']());
      }
      // URL could be provided using a relative path.
      actionCodeSettings['url'] = Uri.resolve(
          util.getCurrentUrl(),
          actionCodeSettings['url']).toString();
      return actionCodeSettings;
    }
    return null;
  }
@return {?firebase.auth.ActionCodeSettings} The ActionCodeSettings if
    email link sign-in is enabled. Null is returned otherwise.