constructor() {
    /**
     * @type {string=} The url to pass to the fetchLater() call.
     */
    this.targetUrl;

    /**
     * @type {string=} The uuid to wait for. Must also be part of `targetUrl`.
     */
    this.uuid;

    /**
     * @type {number=} The activateAfter field of DeferredRequestInit to pass
     * to the fetchLater() call.
     * https://whatpr.org/fetch/1647.html#dictdef-deferredrequestinit
     */
    this.activateAfter;

    /**
     * @type {string=} The method field of DeferredRequestInit to pass to the
     * fetchLater() call.
     * https://whatpr.org/fetch/1647.html#dictdef-deferredrequestinit
     */
    this.method;

    /**
     * @type {string=} The referrer field of DeferredRequestInit to pass to the
     * fetchLater() call.
     * https://whatpr.org/fetch/1647.html#requestinit
     */
    this.referrer;

    /**
     * @type {string=} One of the `BeaconDataType` to tell the iframe how to
     * generate the body for its fetchLater() call.
     */
    this.bodyType;

    /**
     * @type {number=} The size to tell the iframe how to generate the body of
     * its fetchLater() call.
     */
    this.bodySize;

    /**
     * @type {bool} Whether to set allow="deferred-fetch" attribute for the
     * iframe. Combing with a Permissions-Policy header, this will enable
     * fetchLater() being used in a cross-origin iframe.
     */
    this.allowDeferredFetch;

    /**
     * @type {FetchLaterIframeExpectation=} The expectation on the iframe's
     * behavior.
     */
    this.expect;
  }
The options to configure a fetchLater() call in an iframe.
@record