Reduced with m-c:
BuildID=20191230214931
SourceStamp=03ed5ed6cba7190608c548578e9d79d82b0ccf83

Assertion failure: !layerClip || !aLayer->Combines3DTransformWithAncestors() (The layer with a clip should not participate a 3D rendering context), at gfx/layers/composite/LayerManagerComposite.cpp:372

#0 mozilla::layers::LayerManagerComposite::PostProcessLayers src\gfx\layers\composite\LayerManagerComposite.cpp:370
#1 mozilla::layers::LayerManagerComposite::PostProcessLayers src\gfx\layers\composite\LayerManagerComposite.cpp:435
#2 mozilla::layers::LayerManagerComposite::PostProcessLayers src\gfx\layers\composite\LayerManagerComposite.cpp:435
#3 mozilla::layers::LayerManagerComposite::PostProcessLayers src\gfx\layers\composite\LayerManagerComposite.cpp:435
#4 mozilla::layers::LayerManagerComposite::PostProcessLayers src\gfx\layers\composite\LayerManagerComposite.cpp:435
#5 mozilla::layers::LayerManagerComposite::PostProcessLayers src\gfx\layers\composite\LayerManagerComposite.cpp:340
#6 mozilla::layers::LayerManagerComposite::UpdateAndRender src\gfx\layers\composite\LayerManagerComposite.cpp:587
#7 mozilla::layers::LayerManagerComposite::EndTransaction src\gfx\layers\composite\LayerManagerComposite.cpp:564
#8 mozilla::layers::CompositorBridgeParent::CompositeToTarget src\gfx\layers\ipc\CompositorBridgeParent.cpp:1035
#9 mozilla::layers::CompositorVsyncScheduler::Composite src\gfx\layers\ipc\CompositorVsyncScheduler.cpp:250
#10 mozilla::detail::RunnableMethodImpl<mozilla::layers::CompositorVsyncScheduler *,void (mozilla::layers::CompositorVsyncScheduler::*)(mozilla::layers::BaseTransactionId<mozilla::VsyncIdType>, mozilla::TimeStamp),1,mozilla::RunnableKind::Cancelable,mozilla::layers::BaseTransactionId<mozilla::VsyncIdType>,mozilla::TimeStamp>::Run src\obj-firefox\dist\include\nsThreadUtils.h:1217
#11 MessageLoop::RunTask src\ipc\chromium\src\base\message_loop.cc:442
#12 MessageLoop::DeferOrRunPendingTask src\ipc\chromium\src\base\message_loop.cc:450
#13 MessageLoop::DoWork src\ipc\chromium\src\base\message_loop.cc:523
#14 base::MessagePumpForUI::DoRunLoop src\ipc\chromium\src\base\message_pump_win.cc:203
#15 base::MessagePumpWin::Run src\ipc\chromium\src\base\message_pump_win.h:79
#16 MessageLoop::RunInternal src\ipc\chromium\src\base\message_loop.cc:315
#17 MessageLoop::RunHandler src\ipc\chromium\src\base\message_loop.cc:308
#18 MessageLoop::Run src\ipc\chromium\src\base\message_loop.cc:290
#19 base::Thread::ThreadMain src\ipc\chromium\src\base\thread.cc:192
#20 `anonymous namespace'::ThreadFunc src\ipc\chromium\src\base\platform_thread_win.cc:19
#21 __asan::AsanThread::ThreadStart Z:\task_1576855953\fetches\llvm-project\llvm\projects\compiler-rt\lib\asan\asan_thread.cc:262
#22 BaseThreadInitThunk+0x13 (C:\WINDOWS\System32\KERNEL32.DLL+0x180017bd3)
#23 patched_BaseThreadInitThunk src\mozglue\dllservices\WindowsDllBlocklist.cpp:582
#24 RtlUserThreadStart+0x20 (C:\WINDOWS\SYSTEM32\ntdll.dll+0x18006ced0)

bug 1727672