/**
 * Create and cache the iframe.
 *
 * We're caching by domain, in case multiple hub sites are referenced
 * from a single satellite domain.
 *
 * We're returning a promise to avoid a race condition.  If two calls
 * go out for the same iframe, and the second happens before the iframe
 * has loaded, we want the second to also be beholden to the iframe's
 * loading.  The promise is what ensures the iframe has loaded, so we'll
 * need to return that for all subsequent calls.
 */
export declare const getIframe: (iframeUrl: string) => Promise<HTMLIFrameElement>;
/**
 * For testing purposes:
 */
export declare const resetIframes: () => void;