Assertion failure: ancestorTransform.IsIdentity(), at src/gfx/layers/composite/AsyncCompositionManager.cpp:483 #0 mozilla::layers::AsyncCompositionManager::AlignFixedAndStickyLayers(mozilla::layers::Layer*, mozilla::layers::Layer*, unsigned long, mozilla::gfx::Matrix4x4Typed<mozilla::LayerPixel, mozilla::ParentLayerPixel> const&, mozilla::gfx::Matrix4x4Typed<mozilla::LayerPixel, mozilla::ParentLayerPixel> const&, mozilla::gfx::MarginTyped<mozilla::ScreenPixel, float> const&, std::map<mozilla::layers::Layer*, mozilla::layers::AsyncCompositionManager::ClipParts, std::less<mozilla::layers::Layer*>, std::allocator<std::pair<mozilla::layers::Layer* const, mozilla::layers::AsyncCompositionManager::ClipParts> > >*) src/gfx/layers/composite/AsyncCompositionManager.cpp:551:31 #1 mozilla::layers::AsyncCompositionManager::AlignFixedAndStickyLayers(mozilla::layers::Layer*, mozilla::layers::Layer*, unsigned long, mozilla::gfx::Matrix4x4Typed<mozilla::LayerPixel, mozilla::ParentLayerPixel> const&, mozilla::gfx::Matrix4x4Typed<mozilla::LayerPixel, mozilla::ParentLayerPixel> const&, mozilla::gfx::MarginTyped<mozilla::ScreenPixel, float> const&, std::map<mozilla::layers::Layer*, mozilla::layers::AsyncCompositionManager::ClipParts, std::less<mozilla::layers::Layer*>, std::allocator<std::pair<mozilla::layers::Layer* const, mozilla::layers::AsyncCompositionManager::ClipParts> > >*) src/gfx/layers/composite/AsyncCompositionManager.cpp:463:7 #2 mozilla::layers::AsyncCompositionManager::AlignFixedAndStickyLayers(mozilla::layers::Layer*, mozilla::layers::Layer*, unsigned long, mozilla::gfx::Matrix4x4Typed<mozilla::LayerPixel, mozilla::ParentLayerPixel> const&, mozilla::gfx::Matrix4x4Typed<mozilla::LayerPixel, mozilla::ParentLayerPixel> const&, mozilla::gfx::MarginTyped<mozilla::ScreenPixel, float> const&, std::map<mozilla::layers::Layer*, mozilla::layers::AsyncCompositionManager::ClipParts, std::less<mozilla::layers::Layer*>, std::allocator<std::pair<mozilla::layers::Layer* const, mozilla::layers::AsyncCompositionManager::ClipParts> > >*) src/gfx/layers/composite/AsyncCompositionManager.cpp:463:7 #3 mozilla::layers::AsyncCompositionManager::ApplyAsyncContentTransformToTree(mozilla::layers::Layer*, bool*)::$_4::operator()(mozilla::layers::Layer*) const src/gfx/layers/composite/AsyncCompositionManager.cpp:1052:13 #4 _ZN7mozilla6layersL11ForEachNodeINS0_15ForwardIteratorEPNS0_5LayerEZNS0_23AsyncCompositionManager32ApplyAsyncContentTransformToTreeES4_PbE3$_3ZNS5_32ApplyAsyncContentTransformToTreeES4_S6_E3$_4EENS_8EnableIfIXaasr6IsSameIDTclfp0_fp_EEvEE5valuesr6IsSameIDTclfp1_fp_EEvEE5valueEvE4TypeET0_RKT1_RKT2_ src/gfx/layers/TreeTraversal.h:142:5 #5 _ZN7mozilla6layersL11ForEachNodeINS0_15ForwardIteratorEPNS0_5LayerEZNS0_23AsyncCompositionManager32ApplyAsyncContentTransformToTreeES4_PbE3$_3ZNS5_32ApplyAsyncContentTransformToTreeES4_S6_E3$_4EENS_8EnableIfIXaasr6IsSameIDTclfp0_fp_EEvEE5valuesr6IsSameIDTclfp1_fp_EEvEE5valueEvE4TypeET0_RKT1_RKT2_ src/gfx/layers/TreeTraversal.h:142:5 #6 _ZN7mozilla6layersL11ForEachNodeINS0_15ForwardIteratorEPNS0_5LayerEZNS0_23AsyncCompositionManager32ApplyAsyncContentTransformToTreeES4_PbE3$_3ZNS5_32ApplyAsyncContentTransformToTreeES4_S6_E3$_4EENS_8EnableIfIXaasr6IsSameIDTclfp0_fp_EEvEE5valuesr6IsSameIDTclfp1_fp_EEvEE5valueEvE4TypeET0_RKT1_RKT2_ src/gfx/layers/TreeTraversal.h:142:5 #7 mozilla::layers::AsyncCompositionManager::ApplyAsyncContentTransformToTree(mozilla::layers::Layer*, bool*) src/gfx/layers/composite/AsyncCompositionManager.cpp:886:3 #8 mozilla::layers::AsyncCompositionManager::TransformShadowTree(mozilla::TimeStamp, mozilla::BaseTimeDuration<mozilla::TimeDurationValueCalculator>, mozilla::layers::AsyncCompositionManager::TransformsToSkip) src/gfx/layers/composite/AsyncCompositionManager.cpp:1316:9 #9 mozilla::layers::CompositorBridgeParent::CompositeToTarget(mozilla::gfx::DrawTarget*, mozilla::gfx::IntRectTyped<mozilla::gfx::UnknownUnits> const*) src/gfx/layers/ipc/CompositorBridgeParent.cpp:1041:48 #10 mozilla::layers::CompositorVsyncScheduler::Composite(mozilla::TimeStamp) src/gfx/layers/ipc/CompositorVsyncScheduler.cpp:243:27 #11 mozilla::detail::RunnableMethodImpl<mozilla::layers::CompositorVsyncScheduler*, void (mozilla::layers::CompositorVsyncScheduler::*)(mozilla::TimeStamp), true, (mozilla::RunnableKind)1, mozilla::TimeStamp>::Run() src/obj-firefox/dist/include/nsThreadUtils.h:1216:13 #12 MessageLoop::RunTask(already_AddRefed<nsIRunnable>) src/ipc/chromium/src/base/message_loop.cc:452:9 #13 MessageLoop::DeferOrRunPendingTask(MessageLoop::PendingTask&&) src/ipc/chromium/src/base/message_loop.cc:460:5 #14 MessageLoop::DoWork() src/ipc/chromium/src/base/message_loop.cc:535:13 #15 base::MessagePumpDefault::Run(base::MessagePump::Delegate*) src/ipc/chromium/src/base/message_pump_default.cc:36:31 #16 MessageLoop::RunInternal() src/ipc/chromium/src/base/message_loop.cc:326:10 #17 MessageLoop::Run() src/ipc/chromium/src/base/message_loop.cc:299:3 #18 base::Thread::ThreadMain() src/ipc/chromium/src/base/thread.cc:181:16 #19 ThreadFunc(void*) src/ipc/chromium/src/base/platform_thread_posix.cc:38:13 #20 start_thread (/lib/x86_64-linux-gnu/libpthread.so.0+0x76b9) #21 clone /build/glibc-Cl5G7W/glibc-2.23/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:109

I don't know much about how this works but it seems to be from code written in 1288210. Botond, any idea?

This is very similar to the scenario in bug 1430787. I can't really comment on it usefully until Markus answers the questions I asked in bug 1430787 comment 7 and bug 1430787 comment 9.

I am running into this assertion while browsing around webcompat.com in a debug build of Fennec.

This is going to be fixed by bug 1430787.