Crash report: https://crash-stats.mozilla.org/report/index/3971757c-a34b-45a9-a721-204220201026

MOZ_CRASH Reason: MOZ_CRASH(GFX_CRASH)

Top 10 frames of crashing thread:

0 xul.dll CrashStatsLogForwarder::CrashAction gfx/thebes/gfxPlatform.cpp:410
1 xul.dll mozilla::gfx::Log<1, mozilla::gfx::CriticalLogger>::Flush gfx/2d/Logging.h:277
2 xul.dll mozilla::gfx::Log<1, mozilla::gfx::CriticalLogger>::~Log gfx/2d/Logging.h:270
3 xul.dll mozilla::layers::SyncObjectD3D11Client::SynchronizeInternal gfx/layers/d3d11/TextureD3D11.cpp:1747
4 xul.dll mozilla::layers::SyncObjectD3D11ClientContentDevice::Synchronize gfx/layers/d3d11/TextureD3D11.cpp:1837
5 xul.dll mozilla::layers::CompositorBridgeChild::NotifyFinishedAsyncEndLayerTransaction gfx/layers/ipc/CompositorBridgeChild.cpp:1239
6 xul.dll mozilla::layers::PaintThread::AsyncPaintTask gfx/layers/PaintThread.cpp:243
7 xul.dll mozilla::detail::RunnableFunction<`lambda at /builds/worker/checkouts/gecko/gfx/layers/PaintThread.cpp:198:30'>::Run xpcom/threads/nsThreadUtils.h:577
8 xul.dll nsThread::ProcessNextEvent xpcom/threads/nsThread.cpp:1197
9 xul.dll mozilla::ipc::MessagePumpForNonMainThreads::Run ipc/glue/MessagePump.cpp:302

https://bugzilla.mozilla.org/show_bug.cgi?id=1595994 would have changed the signature of this crash, but it's pre-existing.
Failure to take the lock have happened for a while.

Closing because no crashes reported for 12 weeks.