document.implementation.createDocument with current document's DOCTYPE.
On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
PASS doc = document.implementation.createDocument(null, null, document.doctype) did not throw exception.
PASS doc.doctype is doctype
PASS doc.firstChild is doctype
PASS document.doctype is null
PASS successfullyParsed is true
TEST COMPLETE
PASS successfullyParsed is true
TEST COMPLETE