Function wait

test/fixtures/wpt/common/security-features/resources/common.sub.js:703–705

(ms)

 */
async function requestViaSendBeacon(url) {
  function wait(ms) {
    return new Promise(resolve => step_timeout(resolve, ms));
  }
  if (!navigator.sendBeacon(url)) {
    // If mixed-content check fails, it should return false.
    throw new Error('sendBeacon() fails.');