<!DOCTYPE html>
<html>
<body>
<script>
if (window.testRunner)
    testRunner.dumpAsText();

function mutationCallback(mutations, observer) {
    mutations[0].addedNodes[-1];
}

var mutationObserver = new MutationObserver(mutationCallback);
mutationObserver.observe(document.body, {childList: true});
document.body.appendChild(document.createTextNode("PASS. WebKit didn't crash"));
</script>
</body>
</html>