Function installFriendlyIframeEmbed

src/friendly-iframe-embed.js:136–250

(
  iframe,
  container,
  spec,
  opt_preinstallCallback // TODO(#22733): remove "window" argument.
)

 * @return {!Promise<!FriendlyIframeEmbed>}
 */
export function installFriendlyIframeEmbed(
  iframe,
  container,
  spec,
  opt_preinstallCallback // TODO(#22733): remove "window" argument.
) {
  /** @const {!Window} */
  const win = getTopWindow(getWin(iframe));
  /** @const {!./service/extensions-impl.Extensions} */
  const extensionsService = Services.extensionsFor(win);
  /** @const {!./service/ampdoc-impl.AmpDocService} */
  const ampdocService = Services.ampdocServiceFor(win);

  setStyle(iframe, 'visibility', 'hidden');
  iframe.setAttribute('referrerpolicy', 'unsafe-url');
  iframe.setAttribute('marginheight', '0');
  iframe.setAttribute('marginwidth', '0');

  const extensions = spec.extensions || [];

  // Pre-load extensions.
  preloadFriendlyIframeEmbedExtensions(win, extensions);

  const html = spec.skipHtmlMerge ? spec.html : mergeHtml(spec);
  // Receive the signal when iframe is ready: it's document is formed.
  iframe.onload = () => {
    // Chrome does not reflect the iframe readystate.
    iframe.readyState = 'complete';
  };
  const registerViolationListener = () => {
    iframe.contentWindow.addEventListener(
      'securitypolicyviolation',
      (violationEvent) => {
        dev().warn('FIE', 'security policy violation', violationEvent);
      }
    );
  };
  let loadedPromise;
  if (isSrcdocSupported()) {
    iframe.srcdoc = html;
    loadedPromise = loadPromise(iframe);
    container.appendChild(iframe);
    registerViolationListener();
  } else {
    iframe.src = 'about:blank';
    container.appendChild(iframe);
    const childDoc = iframe.contentWindow.document;
    registerViolationListener();
    childDoc.open();
    childDoc.write(devAssert(html));
    // With document.write, `iframe.onload` arrives almost immediately, thus
    // we need to wait for child's `window.onload`.
    loadedPromise = loadPromise(iframe.contentWindow);
    childDoc.close();
  }

  // Wait for document ready signal.
  // This is complicated due to crbug.com/649201 on Chrome and a similar issue