speculation-rules/prerender/resources/background-sync.https.html

<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/speculation-rules/prerender/resources/utils.js"></script>
<script src="/speculation-rules/prerender/resources/deferred-promise-utils.js"></script>
<script>

// The main test page (restriction-background-sync.https.html)
// loads the initiator page, then the initiator page will prerender itself
// with the `prerendering` parameter.
const params = new URLSearchParams(location.search);
const isPrerendering = params.has('prerendering');

if (!isPrerendering) {
  const rule_extras = {'target_hint': getTargetHint()};
  loadInitiatorPage(rule_extras);
} else {
  async function loadPrerenderPage() {
    const prerenderEventCollector = new PrerenderEventCollector();
    const scope = `resources/`;
    const registration = await navigator.serviceWorker.getRegistration(scope);
    const register_promise = registration.periodicSync.register(
        'periodic', { minInterval: 1000 });
    prerenderEventCollector.start(register_promise, 'periodicSync.register');
  }
  loadPrerenderPage();
}

</script>