LayoutTests/http/tests/navigation/resources/page-cache-helper-for-sharedworker.html

This page should go back. If a test outputs the contents of this
page, then the test page failed to enter the page cache.
<script>
var channel = new BroadcastChannel('shared-worker');
async function doTest(counter)
{
    if (!counter)
        counter = 0;
    else if (counter >= 100)
        return;

    channel.postMessage('ping');
    await new Promise((resolve, reject) => {
         let myTimer = setTimeout(resolve, 1000);
         channel.onmessage = async () => {
             clearTimeout(myTimer);
             // We received a message from shared worker, let's call doTest to retry.
             await new Promise(resolve => setTimeout(resolve, 50));
             doTest(++counter).then(resolve, reject);
         };
    });

    const sw2 = new SharedWorker('shared-worker-script.js?2');
    sw2.port.postMessage({ action: 'setState', state: 'hungry' });
    await new Promise(resolve => sw2.port.onmessage = resolve);
}

window.addEventListener("load", async () => {
    await doTest();
    history.back();
}, false);
</script>