Multiple tests are crashing in macOS Debug after 296189@main. 1 0x3002422cc WTF::SingleThreadIntegralWrapper<unsigned int>::assertThread() const 2 0x300242244 WTF::SingleThreadIntegralWrapper<unsigned int>::operator++() 3 0x30024221c WTF::CanMakeCheckedPtrBase<WTF::SingleThreadIntegralWrapper<unsigned int>, unsigned int>::incrementCheckedPtrCount() const 4 0x3022ee728 WTF::CheckedRef<WebCore::ScrollerMac, WTF::RawPtrTraits<WebCore::ScrollerMac>>::CheckedRef(WebCore::ScrollerMac&) 5 0x3022ee6ec WTF::CheckedRef<WebCore::ScrollerMac, WTF::RawPtrTraits<WebCore::ScrollerMac>>::CheckedRef(WebCore::ScrollerMac&) 6 0x3022e4de0 WebCore::ScrollerPairMac::checkedHorizontalScroller() 7 0x3022e589c WebCore::ScrollerPairMac::updateValues() 8 0x3023dc9b0 WebCore::ScrollingTreeScrollingNodeDelegateMac::updateScrollbarLayers() 9 0x12c59e358 WebKit::ScrollingTreeFrameScrollingNodeRemoteMac::repositionRelatedLayers() 10 0x306124330 WebCore::ScrollingTreeScrollingNode::applyLayerPositions() 11 0x3060e4b40 WebCore::ScrollingTree::applyLayerPositionsRecursive(WebCore::ScrollingTreeNode&) 12 0x3060e4afc WebCore::ScrollingTree::applyLayerPositionsInternal() 13 0x12c59e01c WebKit::RemoteScrollingTree::tryToApplyLayerPositions() 14 0x12b9a1498 WebKit::RemoteLayerTreeEventDispatcher::delayedRenderingUpdateDetectionTimerFired() 15 0x12b9b40d4 WebKit::RemoteLayerTreeEventDispatcher::scheduleDelayedRenderingUpdateDetectionTimer(WTF::Seconds)::$_0::operator()() const 16 0x12b9b3e60 WTF::Detail::CallableWrapper<WebKit::RemoteLayerTreeEventDispatcher::scheduleDelayedRenderingUpdateDetectionTimer(WTF::Seconds)::$_0, void>::call() 17 0x129233084 WTF::Function<void ()>::operator()() const 18 0x129232fbc WTF::RunLoop::Timer::fired() 19 0x10b95e988 WTF::RunLoop::TimerBase::start(WTF::Seconds, bool)::$_0::operator()(__CFRunLoopTimer*, void*) const 20 0x10b95e928 WTF::RunLoop::TimerBase::start(WTF::Seconds, bool)::$_0::__invoke(__CFRunLoopTimer*, void*) 21 0x180f5ee14 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ 22 0x180f5ead4 __CFRunLoopDoTimer 23 0x180f5e610 __CFRunLoopDoTimers 24 0x180f44a18 __CFRunLoopRun 25 0x180f43c58 CFRunLoopRunSpecific 26 0x180fbd714 CFRunLoopRun 27 0x10b95d760 WTF::RunLoop::run() 28 0x10b95af70 WTF::RunLoop::create(WTF::ASCIILiteral, WTF::ThreadType, WTF::Thread::QOS)::$_0::operator()() const 29 0x10b95aef0 WTF::Detail::CallableWrapper<WTF::RunLoop::create(WTF::ASCIILiteral, WTF::ThreadType, WTF::Thread::QOS)::$_0, void>::call() 30 0x10b88cdcc WTF::Function<void ()>::operator()() const 31 0x10b9eff90 WTF::Thread::entryPoint(WTF::Thread::NewThreadContext*) Test result: https://ews-build.webkit.org/#/builders/122/builds/25609 History: https://results.webkit.org/?suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&test=http%2Ftests%2Fcache%2Fdisk-cache%2Fshattered-deduplication.html&test=http%2Ftests%2Fswipe%2Fswipe-back-with-outstanding-load-cancellation.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-overscroll-behavior%2Foverscroll-behavior.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-scroll-snap%2Fsnap-at-user-scroll-end.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-values%2Fviewport-units-keyframes.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcssom-view%2Fadd-background-attachment-fixed-during-smooth-scroll.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcssom-view%2Fbackground-change-during-smooth-scroll.html