Description

IE 11 as well as Edge (even 17-18) often crash on the traversing: contents() for <frame /> test with the "Permission denied" error. IE crashes way often than Edge. This is probably related to my Sizzle removal PR (#4395) but I wasn't able to pinpoint the exact reason so far. The error points to line 174 in src/selector.js. An example failing run: https://swarm.jquery.org/result/3337866.

It's hard to debug as it's clearly a race condition. If I run this test in isolation, it always passes.

I think I've seen a similar failure on the 3.4-stable branch as well but it was happening way less often.

We should figure this out before the 4.0.0 release.

Link to test case

N/A, it's a core test already in the repo.