Function installStylesLegacy

testing/iframe.js:301–332

* @param {!Document} doc * @param {string} cssText * @param {function()} cb

(doc, cssText, cb)

 * @param {function()} cb
 */
function installStylesLegacy(doc, cssText, cb) {
  const style = doc.createElement('style');
  style.textContent = cssText;
  doc.head.appendChild(style);

  // Styles aren't always available synchronously. E.g. if there is a
  // pending style download, it will have to finish before the new
  // style is visible.
  // For this reason we poll until the style becomes available.
  // Sync case.
  const styleLoaded = () => {
    const sheets = doc.styleSheets;
    for (let i = 0; i < sheets.length; i++) {
      const sheet = sheets[i];
      if (sheet.ownerNode == style) {
        return true;
      }
    }
    return false;
  };

  if (styleLoaded()) {
    cb();
  } else {
    const interval = setInterval(() => {
      if (styleLoaded()) {
        clearInterval(interval);
        cb();
      }
    }, 4);
  }
}

export function createServedIframe(src) {
  return new Promise(function (resolve, reject) {