ToT, eg r426630, fails these tests because they don't retrieve the constructor's prototype but instead cache it. There's also follow-on steps for invalid prototypes which look up a built-in constructor in a particular global.
I think the remaining failures there are because the upstream test is buggy--yurak noticed it asserts the prototype is HTMLParagraphElement (ie the interface object and not the interface prototype object.)
Comment 1 by dominicc@chromium.org
, Oct 20 2016