third_party/web_platform_tests/XMLHttpRequest/open-url-worker-simple.htm

 <!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>XMLHttpRequest: relative URLs in worker scripts resolved by script URL</title>
    <link rel="stylesheet" href="/resources/testharness.css" />
    <script src="/resources/testharness.js"></script>
    <script src="/resources/testharnessreport.js"></script>
    <link rel="help" href="https://xhr.spec.whatwg.org/#the-open()-method" data-tested-assertations="following::OL[1]/LI[3] following::OL[1]/LI[3]/ol[1]/li[1]" />
</head>
<body>
    <div id="log"></div>
    <script type="text/javascript">
        var test = async_test()
        var worker = new Worker("resources/workerxhr-simple.js")
    	worker.onmessage = function (e) {
            test.step(function(){
                assert_equals(e.data, 'PASSED')
                test.done()
            })
        }
        worker.postMessage('start')
    </script>
</body>
</html>