init_(
      opt_onEmptyResponse, opt_onAccountSelected, opt_onAddAccount,
      opt_providers, opt_language, opt_uiConfig) {
    this.onEmptyResponse_ = opt_onEmptyResponse;
    this.initialized_ = true;
    if (this.acResult_ == null) {
      opt_onEmptyResponse();
    } else if (this.acResult_ instanceof Account) {
      opt_onAccountSelected(
          /** @type {!Account} */ (this.acResult_));
    } else if (this.acResult_ == 'Add account') {
      opt_onAddAccount(this.available_);
    } else {
      throw new Error('unknown accountchooser result.');
    }
  }
@see firebaseui.auth.acClient.init
@private