LayoutTests/http/tests/navigation/cross-origin-iframe-location-hash-reexecute-onload.html

<html>
<head>
<script src="/js-test-resources/js-test.js"></script>
</head>
<body>
<script>
description("This tests that the load event is only fired twice when the location hash is changed in an embedded iframe's window.load.");
jsTestIsAsync = true;

let onloadCount = 0;

window.addEventListener("message", () => {
    if (onloadCount == 2)
        testPassed("onload fired twice.");
    else
        testFailed("onload fired " + onloadCount + " time(s).");

    finishJSTest();
});

function onloadFired() {
    onloadCount++;
}
</script>
<iframe src="http://localhost:8000/navigation/resources/change-location-hash-onload.html" onload="onloadFired()"></iframe>
</body>
</html>