autoUpgradeAnonymousUsers() {
    const autoUpgradeAnonymousUsers =
        !!this.config_.get('autoUpgradeAnonymousUsers');
    // Confirm signInFailure callback is provided when anonymous upgrade is
    // enabled. This is required to provide a means of recovery for merge
    // conflict flows.
    if (autoUpgradeAnonymousUsers && !this.getSignInFailureCallback()) {
      log.error('Missing "signInFailure" callback: ' +
          '"signInFailure" callback needs to be provided when ' +
          '"autoUpgradeAnonymousUsers" is set to true.');
    }
    return autoUpgradeAnonymousUsers;
  }
@return {boolean} Whether to auto upgrade anonymous users.