You can see the results here: https://build.webkit.org/builders/Apple%20Win%207%20Release%20%28Tests%29/builds/48839 Unfortunately I have no idea which revision caused this serious regression, because the Windows bot seems to be unmaintained, because it exits early since approximately a month ago.
marked as failure in r177779 to try to make the bot not to exit early
+info: ------ these tests fail on r176885: https://build.webkit.org/results/Apple%20Win%207%20Release%20%28Tests%29/r176885%20%2848624%29/results.html nobody knows what happens between r176677-r176885, because bots exited early due to crashes caused by r176677 and fixed by r176885 these tests passed on r176674: https://build.webkit.org/builders/Apple%20Win%207%20Release%20%28Tests%29/builds/48553
CSS Regions were removed in Bug 174978.