chromium/fuchsia_web/webengine/test/data/web_worker.html

<!DOCTYPE html>
<meta charset="utf-8">
<!-- Disable favicon fetching. -->
<link rel="icon" href="data:;base64,=">
<title>create a web worker</title>
<script>
    const params = new URLSearchParams(location.search);
    const worker = new Worker(params.get('worker_url'));
    worker.addEventListener("message", (event) => {
        document.title = event.data;
    });
</script>