constructor(googleyolo) {
    /**
     * @private {?SmartLockApi|undefined} The One-Tap instance reference. If no
     *     reference is available, googleyolo will be lazy loaded dynamically.
     */
    this.googleyolo_ = googleyolo || getGoogleAccountsId();
    /**
     * @private {boolean} Whether googleyolo UI has already been initialized.
     */
    this.initialized_ = false;
    /**
     * @private {?function(?SmartLockCredential)} The callback to trigger when
     *     a credential is available or the flow is cancelled.
     */
    this.callback_ = null;
  }
@param {?SmartLockApi=} googleyolo The optional googleyolo reference.
    If no reference provided, the global googleyolo instance is used. If
    that is not available, all supported operations will be no-ops.