See https://github.com/w3c/web-platform-tests/pull/9390 for tests.
Looks like we're failing all the checks at:
The tests seem to expect window.opener to no longer be replaceable. This seems like risky behavior change and I am not sure we want to do this. I had aligned WebKit with the spec via Bug 181505 already (to fix issues with Gmail).
Chris, I assume per https://github.com/whatwg/html/pull/3448#issuecomment-363208579 you now agree with this bug, right?
(In reply to Anne van Kesteren from comment #3)
> Chris, I assume per
> https://github.com/whatwg/html/pull/3448#issuecomment-363208579 you now
> agree with this bug, right?
I think so although I haven't had time to investigate why it is failing.