From the log it looks like there's something wrong with the window causing XGetWindowAttributes to fail. It does this first in CompositorOGL , and then I'm guessing it happens in X11CompositorWidget too . Without the window attributes we wouldn't have a visual which would give us a bad format which causes all the X11WindowSurface creation to fail . It looks like there should be better error handling in X11CompositorWidget to make it clear that XGetWindowAttributes failed. Something is going wrong in the initialization of the window/display in X11CompositorWidget, but I'm not sure if that is from a regression from bug 1289251 or is unrelated. When there is no gpu-process X11CompositorWidget should not be doing anything new with x11 windows/displays than what was already done before.  http://searchfox.org/mozilla-central/source/gfx/gl/GLContextProviderGLX.cpp#1253  http://searchfox.org/mozilla-central/source/widget/gtk/X11CompositorWidget.cpp#32  http://searchfox.org/mozilla-central/source/widget/nsShmImage.cpp#186  http://searchfox.org/mozilla-central/source/widget/gtk/WindowSurfaceX11.cpp#26
25 automation job failures were associated with this bug in the last 7 days. Repository breakdown: * autoland: 14 * try: 5 * mozilla-inbound: 4 * mozilla-central: 1 * fx-team: 1 Platform breakdown: * linux64: 24 * osx-10-10: 1 For more details, see: https://brasstacks.mozilla.com/orangefactor/?display=Bug&bugid=1304659&startday=2016-10-24&endday=2016-10-30&tree=all
Went away around October 28.
9 failures in 864 pushes (0.01 failures/push) were associated with this bug in the last 7 days. Repository breakdown: * try: 6 * mozilla-central: 3 Platform breakdown: * windows10-64-vm: 9 For more details, see: https://brasstacks.mozilla.com/orangefactor/?display=Bug&bugid=1304659&startday=2017-06-05&endday=2017-06-11&tree=all