Bug 221634

imported/w3c/web-platform-tests/shadow-dom/declarative/declarative-shadow-dom-attachment.tentative.html Is consistently crashing on BigSur Debug Wk1 and Wk2. History: https://results.webkit.org/?suite=layout-tests&test=imported%2Fw3c%2Fweb-platform-tests%2Fshadow-dom%2Fdeclarative%2Fdeclarative-shadow-dom-attachment.tentative.html Crash Log: ASSERTION FAILED: m_haveAddedMediaUsageManagerSession ./html/MediaElementSession.cpp(1172) : virtual void WebCore::MediaElementSession::updateMediaUsageIfChanged() 1 0x10c3fdc69 WTFCrash 2 0x12d2a0d0b WTFCrashWithInfo(int, char const*, char const*, int) 3 0x1309d3119 WebCore::MediaElementSession::updateMediaUsageIfChanged() 4 0x12ecde360 auto WebCore::MediaSessionManagerCocoa::scheduleSessionStatusUpdate()::$_8::operator()()::'lambda'(auto&)::operator()<WebCore::PlatformMediaSession>(auto&) const 5 0x12ecde313 WTF::Detail::CallableWrapper<WebCore::MediaSessionManagerCocoa::scheduleSessionStatusUpdate()::$_8::operator()()::'lambda'(auto&), void, WebCore::PlatformMediaSession&>::call(WebCore::PlatformMediaSession&) 6 0x13152697a WTF::Function<void (WebCore::PlatformMediaSession&)>::operator()(WebCore::PlatformMediaSession&) const 7 0x1315240aa WebCore::PlatformMediaSessionManager::forEachSession(WTF::Function<void (WebCore::PlatformMediaSession&)> const&) 8 0x12ecddfbb WebCore::MediaSessionManagerCocoa::scheduleSessionStatusUpdate()::$_8::operator()() 9 0x12ecddf0e WTF::Detail::CallableWrapper<WebCore::MediaSessionManagerCocoa::scheduleSessionStatusUpdate()::$_8, void>::call() 10 0x12d2b60a2 WTF::Function<void ()>::operator()() const 11 0x12d66c7b5 WebCore::GenericTaskQueue<WebCore::Timer>::enqueueTask(WTF::Function<void ()>&&)::'lambda'()::operator()() const 12 0x12d66c5ee WTF::Detail::CallableWrapper<WebCore::GenericTaskQueue<WebCore::Timer>::enqueueTask(WTF::Function<void ()>&&)::'lambda'(), void>::call() 13 0x12d2b60a2 WTF::Function<void ()>::operator()() const 14 0x131488d6f WebCore::TaskDispatcher<WebCore::Timer>::dispatchOneTask() 15 0x131488a45 WebCore::TaskDispatcher<WebCore::Timer>::sharedTimerFired() 16 0x1314903e1 WebCore::TaskDispatcher<WebCore::Timer>::sharedTimer()::$_2::operator()() const 17 0x13149039e WTF::Detail::CallableWrapper<WebCore::TaskDispatcher<WebCore::Timer>::sharedTimer()::$_2, void>::call() 18 0x12d2b60a2 WTF::Function<void ()>::operator()() const 19 0x12d2f907e WebCore::Timer::fired() 20 0x1314e67e4 WebCore::ThreadTimers::sharedTimerFiredInternal() 21 0x1314f3211 WebCore::ThreadTimers::setSharedTimer(WebCore::SharedTimer*)::$_0::operator()() const 22 0x1314f31be WTF::Detail::CallableWrapper<WebCore::ThreadTimers::setSharedTimer(WebCore::SharedTimer*)::$_0, void>::call() 23 0x12d2b60a2 WTF::Function<void ()>::operator()() const 24 0x1314a3eeb WebCore::MainThreadSharedTimer::fired() 25 0x131566886 WebCore::timerFired(__CFRunLoopTimer*, void*) 26 0x7fff2047390d __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ 27 0x7fff204733e8 __CFRunLoopDoTimer 28 0x7fff20472f42 __CFRunLoopDoTimers 29 0x7fff2045957f __CFRunLoopRun 30 0x7fff204586ce CFRunLoopRunSpecific 31 0x10b15ac7a runTest(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) Able to reproduce issue using command: run-webkit-tests imported/w3c/web-platform-tests/shadow-dom/declarative/declarative-shadow-dom-attachment.tentative.html --debug --iterations 1000 -f