chromium/third_party/blink/web_tests/external/wpt/speculation-rules/prerender/resources/push.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>

const params = new URLSearchParams(location.search);

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

if (!isPrerendering) {
  loadInitiatorPage();
} else {
  async function loadPrerenderPage() {
    const prerenderEventCollector = new PrerenderEventCollector();
    const scope = `resources/`;
    const registration = await navigator.serviceWorker.getRegistration(scope);
    const subscribe_promise = registration.pushManager.subscribe({
          userVisibleOnly: true,
          applicationServerKey: new TextEncoder().encode('0987654321')
    });
    prerenderEventCollector.start(subscribe_promise, 'pushManager.subscribe');
  }
  loadPrerenderPage();
}

</script>