Fyrd/caniuse — pull request #459 by MayhemYDG (2014-02-26 16:45:50+00:00)
Title: CSS variables are disabled on non-release builds

https://bugzilla.mozilla.org/show_bug.cgi?id=957833

Looks like I missed that part, teehee.
https://bugzilla.mozilla.org/show_bug.cgi?id=773296#c182