Got this backtrace on ToT (linux) while loading many media files at the same time.

#0 0x7fbf546f428d base::debug::StackTrace::StackTrace()
#1 0x7fbf546f265c base::debug::StackTrace::StackTrace()
#2 0x7fbf546f3c45 base::debug::(anonymous namespace)::StackDumpSignalHandler()
#3 0x7fbf54d4d330 <unknown>
#4 0x7fbf40f9960c blink::AudioDestination::IsRenderingThread()
#5 0x7fbf40f997da blink::AudioDestination::RequestRenderOnWebThread()
#6 0x7fbf40f9ba4b _ZN4base8internal13FunctorTraitsIMN5blink16AudioDestinationEFvmmddmEvE6InvokeIPS3_JRKmSA_RKdSC_SA_EEEvS5_OT_DpOT0_
#7 0x7fbf40f9b913 _ZN4base8internal12InvokeHelperILb0EvE8MakeItSoIRKMN5blink16AudioDestinationEFvmmddmEJPS5_RKmSC_RKdSE_SC_EEEvOT_DpOT0_
#8 0x7fbf40f9b846 _ZN4base8internal7InvokerINS0_9BindStateIMN5blink16AudioDestinationEFvmmddmEJN3WTF17UnretainedWrapperIS4_LNS7_22FunctionThreadAffinityE0EEEmmddmEEEFvvEE7RunImplIRKS6_RKNSt3__15tupleIJSA_mmddmEEEJLm0ELm1ELm2ELm3ELm4ELm5EEEEvOT_OT0_NS_13IndexSequenceIJXspT1_EEEE
#9 0x7fbf40f9b5dc _ZN4base8internal7InvokerINS0_9BindStateIMN5blink16AudioDestinationEFvmmddmEJN3WTF17UnretainedWrapperIS4_LNS7_22FunctionThreadAffinityE0EEEmmddmEEEFvvEE3RunEPNS0_13BindStateBaseE
#10 0x7fbf40f7d81d _ZNKR4base8CallbackIFvvELNS_8internal8CopyModeE1ELNS2_10RepeatModeE1EE3RunEv
#11 0x7fbf40f7d7b9 WTF::Function<>::operator()()
#12 0x7fbf40f7ba45 blink::(anonymous namespace)::RunCrossThreadClosure()
#13 0x7fbf40f7e1ce _ZN4base8internal13FunctorTraitsIPFvNSt3__110unique_ptrIN3WTF8FunctionIFvvELNS4_22FunctionThreadAffinityE0EEENS2_14default_deleteIS8_EEEEEvE6InvokeIJSB_EEEvSD_DpOT_
#14 0x7fbf40f7e060 _ZN4base8internal12InvokeHelperILb0EvE8MakeItSoIRKPFvNSt3__110unique_ptrIN3WTF8FunctionIFvvELNS6_22FunctionThreadAffinityE0EEENS4_14default_deleteISA_EEEEEJSD_EEEvOT_DpOT0_
#15 0x7fbf40f7df54 _ZN4base8internal7InvokerINS0_9BindStateIPFvNSt3__110unique_ptrIN3WTF8FunctionIFvvELNS5_22FunctionThreadAffinityE0EEENS3_14default_deleteIS9_EEEEEJNS0_13PassedWrapperISC_EEEEES7_E7RunImplIRKSE_RKNS3_5tupleIJSG_EEEJLm0EEEEvOT_OT0_NS_13IndexSequenceIJXspT1_EEEE
#16 0x7fbf40f7de8c _ZN4base8internal7InvokerINS0_9BindStateIPFvNSt3__110unique_ptrIN3WTF8FunctionIFvvELNS5_22FunctionThreadAffinityE0EEENS3_14default_deleteIS9_EEEEEJNS0_13PassedWrapperISC_EEEEES7_E3RunEPNS0_13BindStateBaseE
#17 0x7fbf5469f941 _ZNO4base8CallbackIFvvELNS_8internal8CopyModeE0ELNS2_10RepeatModeE0EE3RunEv
#18 0x7fbf546f8da7 base::debug::TaskAnnotator::RunTask()
#19 0x7fbf4145628a blink::scheduler::TaskQueueManager::ProcessTaskFromWorkQueue()
#20 0x7fbf4145141a blink::scheduler::TaskQueueManager::DoWork()
#21 0x7fbf4145e307 _ZN4base8internal13FunctorTraitsIMN5blink9scheduler16TaskQueueManagerEFvbEvE6InvokeIRKNS_7WeakPtrIS4_EEJRKbEEEvS6_OT_DpOT0_
#22 0x7fbf4145e265 _ZN4base8internal12InvokeHelperILb1EvE8MakeItSoIRKMN5blink9scheduler16TaskQueueManagerEFvbERKNS_7WeakPtrIS6_EEJRKbEEEvOT_OT0_DpOT1_
#23 0x7fbf4145e1dd _ZN4base8internal7InvokerINS0_9BindStateIMN5blink9scheduler16TaskQueueManagerEFvbEJNS_7WeakPtrIS5_EEbEEEFvvEE7RunImplIRKS7_RKNSt3__15tupleIJS9_bEEEJLm0ELm1EEEEvOT_OT0_NS_13IndexSequenceIJXspT1_EEEE
#24 0x7fbf4145e0ec _ZN4base8internal7InvokerINS0_9BindStateIMN5blink9scheduler16TaskQueueManagerEFvbEJNS_7WeakPtrIS5_EEbEEEFvvEE3RunEPNS0_13BindStateBaseE
#25 0x7fbf5469f941 _ZNO4base8CallbackIFvvELNS_8internal8CopyModeE0ELNS2_10RepeatModeE0EE3RunEv
#26 0x7fbf546f8da7 base::debug::TaskAnnotator::RunTask()
#27 0x7fbf547b145d base::MessageLoop::RunTask()
#28 0x7fbf547b16e7 base::MessageLoop::DeferOrRunPendingTask()
#29 0x7fbf547b246a base::MessageLoop::DoWork()
#30 0x7fbf547b8d68 base::MessagePumpDefault::Run()
#31 0x7fbf547b0d84 base::MessageLoop::Run()
#32 0x7fbf548656ed base::RunLoop::Run()
#33 0x7fbf54931074 base::Thread::Run()
#34 0x7fbf54931c92 base::Thread::ThreadMain()
#35 0x7fbf54912e61 base::(anonymous namespace)::ThreadFunc()
#36 0x7fbf54d45184 start_thread
#37 0x7fbf3e407ffd clone
  r8: 7ed6b8a7b9a25500  r9: 00002a47c442abfe r10: 00002a47c442abb0 r11: 00002a47c442abb8
 r12: 0000000000000000 r13: 0000000000000000 r14: 00007fbf2269c9c0 r15: 00007fbf2269c700
  di: 00002b707fd12c48  si: 0000000000000200  bp: 00007fbf22698310  bx: 0000000000000000
  dx: 0000000000000200  ax: 0000000000000000  cx: 00007fbf54b28700  sp: 00007fbf226982e0
  ip: 00007fbf40f9960c efl: 0000000000010206 cgf: 0000000000000033 erf: 0000000000000004
 trp: 000000000000000e msk: 0000000000000000 cr2: 0000000000000000
[end of stack trace]

I don't have a reliable repro yet, but I can provide more details if needed.