This fails in STP 178 http://wpt.live/css/css-variables/variable-definition.html but according to Bug 250506 https://github.com/WebKit/WebKit/commit/7a3b462e1d002afff41928f1324c7a9477426d19 It seems it was passing. So this regressed in between 7a3b462 and now.
<rdar://problem/115467218>
Though at the same time when I try locally this is working. I'm confused.
<rdar://problem/115467388>