Our support for @supports is pretty good (see https://bugs.webkit.org/show_bug.cgi?id=137569).
I think we should enable it everywhere, and thus remove the compile time guard.
Created attachment 239571 [details]
Created attachment 239573 [details]
I'm not sure why the patch isn't applying. It works fine here.
Created attachment 239575 [details]
Created attachment 239576 [details]
Comment on attachment 239576 [details]
It's interesting that the "skips" were removed from the WinCairo port, but no the actual Apple Windows port. I think these should be enabled on Apple Windows as well.
*** Bug 116554 has been marked as a duplicate of this bug. ***