Function preconnectToOrigin

src/preconnect.js:334–345

(document)

 * @return {Promise} When work is done.
 */
export function preconnectToOrigin(document) {
  return whenDocumentComplete(document).then(() => {
    const win = document.defaultView;
    if (win) {
      const preconnect = Services.preconnectFor(win);
      const info = Services.documentInfoForDoc(document.documentElement);
      const ampdoc = Services.ampdoc(document);
      preconnect.url(ampdoc, info.sourceUrl);
      preconnect.url(ampdoc, info.canonicalUrl);
    }
  });
}