1 Tests the element upgrade algorithm.
3 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
6 PASS host.firstChild instanceof A is true
7 PASS element instanceof B is true
9 PASS element instanceof C is false
10 PASS Object.getPrototypeOf(element) is HTMLElement.prototype
11 PASS host.firstChild instanceof D is false
12 PASS document.querySelector(":unresolved") is host.firstChild
13 PASS upgradedOrder is ["e1","e2","e3","e4","e5"]
14 PASS successfullyParsed is true