https://bugs.freedesktop.org/show_bug.cgi?id=65193
--- Comment #2 from Alexandre Demers alexandre.f.demers@gmail.com --- (In reply to comment #1)
It seems the identified failed assertion is not the prime root of Gnome Shell and KDE not launching. A previous commit must be the culprit for the other problem (I'm tracking it down right now). However, commit 5de41575a127eb8a6a0fe5c71a73b372f9b89f53 does prevent glxgears from running as it should.
Forget about what I just said, I made a mistake, wrongly resync before last build. Retesting right away.