Function preloadBootstrap

src/3p-frame.js:203–210

(win, type, ampdoc, preconnect)

 * @param {!./preconnect.PreconnectService} preconnect
 */
export function preloadBootstrap(win, type, ampdoc, preconnect) {
  const url = getBootstrapBaseUrl(win, ampdoc);
  preconnect.preload(ampdoc, url, 'document');

  // While the URL may point to a custom domain, this URL will always be
  // fetched by it.
  preconnect.preload(ampdoc, getBootstrapUrl(type), 'script');
}

/**
 * Returns the base URL for 3p bootstrap iframes.