<script>
var doc = document.implementation.createHTMLDocument('a');
var b = document.createElement('b');
// Give it a node list cache on document
b.childNodes;

// Attach it to doc to update m_document
doc.adoptNode(b);
doc.body.appendChild(b);
doc.body.removeChild(b);
</script>
<p>Close the document to see if there's an assertion failure.</p>