Reduced with m-c:
BuildID=20191004213811
SourceStamp=74c62117e3e5215f69a07e5ba0adddae33773060

Assertion failure: cachedStyles[i]->EqualForCachedAnonymousContentStyle(*cs) (cached anonymous content styles should be identical to those we would compute normally), at src/layout/base/nsCSSFrameConstructor.cpp:4026

#0 nsCSSFrameConstructor::GetAnonymousContent(nsIContent*, nsIFrame*, nsTArray<nsIAnonymousContentCreator::ContentInfo>&) src/layout/base/nsCSSFrameConstructor.cpp:4006:38
#1 nsCSSFrameConstructor::BeginBuildingScrollFrame(nsFrameConstructorState&, nsIContent*, mozilla::ComputedStyle*, nsContainerFrame*, mozilla::PseudoStyleType, bool, nsContainerFrame*&) src/layout/base/nsCSSFrameConstructor.cpp:4267:7
#2 nsCSSFrameConstructor::BuildScrollFrame(nsFrameConstructorState&, nsIContent*, mozilla::ComputedStyle*, nsIFrame*, nsContainerFrame*, nsContainerFrame*&) src/layout/base/nsCSSFrameConstructor.cpp:4340:48
#3 nsCSSFrameConstructor::ConstructFrameFromItemInternal(nsCSSFrameConstructor::FrameConstructionItem&, nsFrameConstructorState&, nsContainerFrame*, nsFrameList&) src/layout/base/nsCSSFrameConstructor.cpp:3663:7
#4 nsCSSFrameConstructor::ConstructFramesFromItem(nsFrameConstructorState&, nsCSSFrameConstructor::FrameConstructionItemList::Iterator&, nsContainerFrame*, nsFrameList&) src/layout/base/nsCSSFrameConstructor.cpp:5753:3
#5 nsCSSFrameConstructor::ConstructFramesFromItemList(nsFrameConstructorState&, nsCSSFrameConstructor::FrameConstructionItemList&, nsContainerFrame*, bool, nsFrameList&) src/layout/base/nsCSSFrameConstructor.cpp:9619:5
#6 nsCSSFrameConstructor::ProcessChildren(nsFrameConstructorState&, nsIContent*, mozilla::ComputedStyle*, nsContainerFrame*, bool, nsFrameList&, bool, PendingBinding*, nsIFrame*) src/layout/base/nsCSSFrameConstructor.cpp:9788:3
#7 nsCSSFrameConstructor::ConstructBlock(nsFrameConstructorState&, nsIContent*, nsContainerFrame*, nsContainerFrame*, mozilla::ComputedStyle*, nsContainerFrame**, nsFrameList&, nsIFrame*, PendingBinding*) src/layout/base/nsCSSFrameConstructor.cpp:10681:3
#8 nsCSSFrameConstructor::ConstructNonScrollableBlockWithConstructor(nsFrameConstructorState&, nsCSSFrameConstructor::FrameConstructionItem&, nsContainerFrame*, nsStyleDisplay const*, nsFrameList&, nsBlockFrame* (*)(mozilla::PresShell*, mozilla::ComputedStyle*)) src/layout/base/nsCSSFrameConstructor.cpp:4687:3
#9 nsCSSFrameConstructor::ConstructNonScrollableBlock(nsFrameConstructorState&, nsCSSFrameConstructor::FrameConstructionItem&, nsContainerFrame*, nsStyleDisplay const*, nsFrameList&) src/layout/base/nsCSSFrameConstructor.cpp:4658:10
#10 nsCSSFrameConstructor::ConstructFrameFromItemInternal(nsCSSFrameConstructor::FrameConstructionItem&, nsFrameConstructorState&, nsContainerFrame*, nsFrameList&) src/layout/base/nsCSSFrameConstructor.cpp:3638:16
#11 nsCSSFrameConstructor::ConstructFramesFromItem(nsFrameConstructorState&, nsCSSFrameConstructor::FrameConstructionItemList::Iterator&, nsContainerFrame*, nsFrameList&) src/layout/base/nsCSSFrameConstructor.cpp:5753:3
#12 nsCSSFrameConstructor::ConstructFramesFromItemList(nsFrameConstructorState&, nsCSSFrameConstructor::FrameConstructionItemList&, nsContainerFrame*, bool, nsFrameList&) src/layout/base/nsCSSFrameConstructor.cpp:9619:5
#13 nsCSSFrameConstructor::ProcessChildren(nsFrameConstructorState&, nsIContent*, mozilla::ComputedStyle*, nsContainerFrame*, bool, nsFrameList&, bool, PendingBinding*, nsIFrame*) src/layout/base/nsCSSFrameConstructor.cpp:9788:3
#14 nsCSSFrameConstructor::ConstructBlock(nsFrameConstructorState&, nsIContent*, nsContainerFrame*, nsContainerFrame*, mozilla::ComputedStyle*, nsContainerFrame**, nsFrameList&, nsIFrame*, PendingBinding*) src/layout/base/nsCSSFrameConstructor.cpp:10681:3
#15 nsCSSFrameConstructor::ConstructDocElementFrame(mozilla::dom::Element*, nsILayoutHistoryState*) src/layout/base/nsCSSFrameConstructor.cpp:2418:5
#16 nsCSSFrameConstructor::ContentRangeInserted(nsIContent*, nsIContent*, nsILayoutHistoryState*, nsCSSFrameConstructor::InsertionKind) src/layout/base/nsCSSFrameConstructor.cpp:7088:9
#17 nsCSSFrameConstructor::RecreateFramesForContent(nsIContent*, nsCSSFrameConstructor::InsertionKind) src/layout/base/nsCSSFrameConstructor.cpp:8761:7
#18 mozilla::RestyleManager::ProcessRestyledFrames(nsStyleChangeList&) src/layout/base/RestyleManager.cpp:1567:25
#19 mozilla::RestyleManager::DoProcessPendingRestyles(mozilla::ServoTraversalFlags) src/layout/base/RestyleManager.cpp:3115:9
#20 mozilla::PresShell::DoFlushPendingNotifications(mozilla::ChangesToFlush) src/layout/base/PresShell.cpp:4111:39
#21 nsRefreshDriver::Tick(mozilla::layers::BaseTransactionId<mozilla::VsyncIdType>, mozilla::TimeStamp) src/layout/base/nsRefreshDriver.cpp:1983:22
#22 mozilla::RefreshDriverTimer::TickRefreshDrivers(mozilla::layers::BaseTransactionId<mozilla::VsyncIdType>, mozilla::TimeStamp, nsTArray<RefPtr<nsRefreshDriver> >&) src/layout/base/nsRefreshDriver.cpp:350:7
#23 mozilla::RefreshDriverTimer::Tick(mozilla::layers::BaseTransactionId<mozilla::VsyncIdType>, mozilla::TimeStamp) src/layout/base/nsRefreshDriver.cpp:367:5
#24 mozilla::VsyncRefreshDriverTimer::RefreshDriverVsyncObserver::TickRefreshDriver(mozilla::layers::BaseTransactionId<mozilla::VsyncIdType>, mozilla::TimeStamp) src/layout/base/nsRefreshDriver.cpp:727:16
#25 mozilla::VsyncRefreshDriverTimer::RefreshDriverVsyncObserver::NotifyVsync(mozilla::VsyncEvent const&) src/layout/base/nsRefreshDriver.cpp:622:9
#26 mozilla::layout::VsyncChild::RecvNotify(mozilla::VsyncEvent const&) src/layout/ipc/VsyncChild.cpp:65:16
#27 mozilla::layout::PVsyncChild::OnMessageReceived(IPC::Message const&) src/obj-firefox/ipc/ipdl/PVsyncChild.cpp:187:54
#28 mozilla::ipc::PBackgroundChild::OnMessageReceived(IPC::Message const&) src/obj-firefox/ipc/ipdl/PBackgroundChild.cpp:5876:32
#29 mozilla::ipc::MessageChannel::DispatchAsyncMessage(mozilla::ipc::ActorLifecycleProxy*, IPC::Message const&) src/ipc/glue/MessageChannel.cpp:2185:25
#30 mozilla::ipc::MessageChannel::DispatchMessage(IPC::Message&&) src/ipc/glue/MessageChannel.cpp:2109:9
#31 mozilla::ipc::MessageChannel::RunMessage(mozilla::ipc::MessageChannel::MessageTask&) src/ipc/glue/MessageChannel.cpp:1954:3
#32 mozilla::ipc::MessageChannel::MessageTask::Run() src/ipc/glue/MessageChannel.cpp:1985:13
#33 nsThread::ProcessNextEvent(bool, bool*) src/xpcom/threads/nsThread.cpp:1225:14
#34 NS_ProcessNextEvent(nsIThread*, bool) src/xpcom/threads/nsThreadUtils.cpp:486:10
#35 mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) src/ipc/glue/MessagePump.cpp:88:21
#36 MessageLoop::RunInternal() src/ipc/chromium/src/base/message_loop.cc:315:10
#37 MessageLoop::Run() src/ipc/chromium/src/base/message_loop.cc:290:3
#38 nsBaseAppShell::Run() src/widget/nsBaseAppShell.cpp:137:27
#39 XRE_RunAppShell() src/toolkit/xre/nsEmbedFunctions.cpp:934:20
#40 mozilla::ipc::MessagePumpForChildProcess::Run(base::MessagePump::Delegate*) src/ipc/glue/MessagePump.cpp:238:9
#41 MessageLoop::RunInternal() src/ipc/chromium/src/base/message_loop.cc:315:10
#42 MessageLoop::Run() src/ipc/chromium/src/base/message_loop.cc:290:3
#43 XRE_InitChildProcess(int, char**, XREChildData const*) src/toolkit/xre/nsEmbedFunctions.cpp:769:34
#44 content_process_main(mozilla::Bootstrap*, int, char**) src/browser/app/../../ipc/contentproc/plugin-container.cpp:56:28
#45 main src/browser/app/nsBrowserApp.cpp:272:18

A Pernosco session is available here: https://pernos.co/debug/dsJfw4cfXOv6aqVUFEZUdQ/index.html
Note: The session will expire in 7 days.

The fuzzers are hitting this fairly frequently.

Please ping me to get the Pernosco session reactivated.

Cam, do you have cycles to look at this and unblock the fuzzers?

(In reply to Tyson Smith [:tsmith] from comment #2)

The fuzzers are hitting this fairly frequently.

Tyson, are we no longer using the fuzzblocker tag on that kind of bugs so they can be prioritized? We shouldn't be blocking fuzzers :(

(In reply to Emilio Cobos Álvarez (:emilio) from comment #3)

Tyson, are we no longer using the fuzzblocker tag on that kind of bugs so they can be prioritized? We shouldn't be blocking fuzzers :(

Yes we are still using fuzzblocker. This issue is frequent but I wouldn't consider it a fuzzblocker at this point. Hopefully it can be fixed sooner than later but it's not worth sounding the alarm :)

https://hg.mozilla.org/mozilla-central/rev/44a3e5f050de

Is there a real-world user impact to this bug which would justify backport consideration or can this fix ride Fx72 to release?

Too late for 71 at this point.