I've begun seeing a check fail in ResourceProvider::TransferResource, where the source is not allocated. So far seen in Mojo FYI runs of mash_browser_tests.

fsamuel@ cc-ed for help triaging.


[0808/010202.634452:FATAL:resource_provider.cc(1692)] Check failed: source->allocated. 
#0 0x0000034bfb1c base::debug::StackTrace::StackTrace()
#1 0x0000034d860c logging::LogMessage::~LogMessage()
#2 0x000004acea23 cc::ResourceProvider::TransferResource()
#3 0x000004ace738 cc::ResourceProvider::PrepareSendToParent()
#4 0x000004a7dfc4 cc::LayerTreeHostImpl::DrawLayers()
#5 0x000004b17b48 cc::SingleThreadProxy::DoComposite()
#6 0x000004b18810 cc::SingleThreadProxy::ScheduledActionDrawIfPossible()
#7 0x000004b27b24 cc::Scheduler::DrawIfPossible()
#8 0x000004b24cfb cc::Scheduler::ProcessScheduledActions()
#9 0x000004b249c0 cc::Scheduler::OnBeginImplFrameDeadline()
#10 0x000000696b44 _ZN4base8internal7InvokerINS0_9BindStateIMN12_GLOBAL__N_116SimpleHttpServer10ConnectionEFvvEJNS_7WeakPtrIS5_EEEEEFvvEE7RunOnceEPNS0_13BindStateBaseE
#11 0x000000696b44 _ZN4base8internal7InvokerINS0_9BindStateIMN12_GLOBAL__N_116SimpleHttpServer10ConnectionEFvvEJNS_7WeakPtrIS5_EEEEEFvvEE7RunOnceEPNS0_13BindStateBaseE
#12 0x0000034c02b0 base::debug::TaskAnnotator::RunTask()
#13 0x0000034dfca9 base::MessageLoop::RunTask()
#14 0x0000034dffce base::MessageLoop::DeferOrRunPendingTask()
#15 0x0000034e02a9 base::MessageLoop::DoWork()
#16 0x0000034e27f9 base::MessagePumpLibevent::Run()
#17 0x0000034df712 base::MessageLoop::Run()
#18 0x000003509b3a base::RunLoop::Run()
#19 0x0000034b0c42 (anonymous namespace)::StartEmbeddedService()
#20 0x000002193b0d _ZN4base8internal7InvokerINS0_9BindStateIPFvN4mojo16InterfaceRequestIN5blink5mojom19KeyboardLockServiceEEEEJEEES9_E3RunEPNS0_13BindStateBaseEOS8_
#21 0x000001e92256 service_manager::RunStandaloneService()
#22 0x0000034b0a8e RunMashBrowserTests()
#23 0x0000034b0627 main
#24 0x7ffa330c2f45 __libc_start_main
#25 0x0000005874b3 <unknown>
Received signal 6
#0 0x0000034bfb1c base::debug::StackTrace::StackTrace()
#1 0x0000034bf611 base::debug::(anonymous namespace)::StackDumpSignalHandler()
#2 0x7ffa33479330 <unknown>
#3 0x7ffa330d7c37 gsignal
#4 0x7ffa330db028 abort
#5 0x0000034be315 [0808/010202.806822:INFO:service_process_launcher.cc(191)] Launched child process pid=16555, instance=, name=test_ime_driver, user_id=99ee5d0a-49b8-414d-be20-76c5981d733d
base::debug::BreakDebugger()
#6 0x0000034d8ab2 logging::LogMessage::~LogMessage()
#7 0x000004acea23 cc::ResourceProvider::TransferResource()
#8 0x000004ace738 [0808/010202.830461:ERROR:layer_tree_host_impl.cc(2415)] Forcing zero-copy tile initialization as worker context is missing
cc::ResourceProvider::PrepareSendToParent()
#9 0x000004a7dfc4 cc::LayerTreeHostImpl::DrawLayers()[0808/010202.846863:ERROR:shell_delegate_mus.cc(50)] Not implemented reached in virtual bool ash::ShellDelegateMus::CanShowWindowForUser(aura::Window *) const
#10 0x000004b17b48 [0808/010202.851439:ERROR:layer_tree_host_impl.cc(2415)] Forcing zero-copy tile initialization as worker context is missing
cc::SingleThreadProxy::DoComposite()
#11 0x000004b18810 [0808/010202.861262:ERROR:shell_delegate_mus.cc(113)] Not implemented reached in virtual ash::GPUSupport *ash::ShellDelegateMus::CreateGPUSupport()
[0808/010202.861458:ERROR:shell_delegate_mus.cc(102)] Not implemented reached in virtual std::unique_ptr<PaletteDelegate> ash::ShellDelegateMus::CreatePaletteDelegate()
[0808/010202.861479:ERROR:shell_delegate_mus.cc(60)] Not implemented reached in virtual void ash::ShellDelegateMus::PreInit()
[0808/010202.862951:INFO:service_process_launcher.cc(191)] Launched child process pid=16579, instance=, name=content_packaged_services, user_id=6ea5c91a-102a-48cf-b3e8-2766c8e27b2a
cc::SingleThreadProxy::ScheduledActionDrawIfPossible()
#12 0x000004b27b24 [0808/010202.869013:INFO:service_process_launcher.cc(191)] Launched child process pid=16588, instance=, name=font_service, user_id=505C0EE9-3013-43C0-82B0-A84F50CF8D84
cc::Scheduler::DrawIfPossible()
#13 0x000004b24cfb cc::Scheduler::ProcessScheduledActions()
#14 0x000004b249c0 cc::Scheduler::OnBeginImplFrameDeadline()
#15 0x000000696b44 _ZN4base8internal7InvokerINS0_9BindStateIMN12_GLOBAL__N_116SimpleHttpServer10ConnectionEFvvEJNS_7WeakPtrIS5_EEEEEFvvEE7RunOnceEPNS0_13BindStateBaseE
#16[0808/010202.893068:INFO:service_process_launcher.cc(191)] Launched child process pid=16607, instance=, name=ui, user_id=1fbcffa3-c6e4-4a97-afed-f792f9d9b5e8
 0x000000696b44 _ZN4base8internal7InvokerINS0_9BindStateIMN12_GLOBAL__N_116SimpleHttpServer10ConnectionEFvvEJNS_7WeakPtrIS5_EEEEEFvvEE7RunOnceEPNS0_13BindStateBaseE
#17 0x0000034c02b0 base::debug::TaskAnnotator::RunTask()
#18 0x0000034dfca9 base::MessageLoop::RunTask()
#19 0x0000034dffce base::MessageLoop::DeferOrRunPendingTask()
#20 0x0000034e02a9 [0808/010202.922417:ERROR:layer_tree_host_impl.cc(2415)] Forcing zero-copy tile initialization as worker context is missing
base::MessageLoop::DoWork()
#21 0x0000034e27f9 [0808/010202.936589:ERROR:shell_delegate_mus.cc(50)] Not implemented reached in virtual bool ash::ShellDelegateMus::CanShowWindowForUser(aura::Window *) const
base::MessagePumpLibevent::Run()
#22 0x0000034df712 [0808/010202.938551:ERROR:layer_tree_host_impl.cc(2415)] Forcing zero-copy tile initialization as worker context is missing
base::MessageLoop::Run()
#23 0x000003509b3a base::RunLoop::Run()
#24 0x0000034b0c42 (anonymous namespace)::StartEmbeddedService()
#25 0x000002193b0d _ZN4base8internal7InvokerINS0_9BindStateIPFvN4mojo16InterfaceRequestIN5blink5mojom19KeyboardLockServiceEEEEJEEES9_E3RunEPNS0_13BindStateBaseEOS8_
#26 0x000001e92256 service_manager::RunStandaloneService()
#27 0x0000034b0a8e RunMashBrowserTests()
#28 0x0000034b0627 main
#29 0x7ffa330c2f45 __libc_start_main
#30 0x0000005874b3 <unknown>
  r8: ffff9226e707dc50  r9: ffff9226e707dc40 r10: 0000000000000008 r11: 0000000000000206
 r12: 00007ffe6cbaa880 r13: 00007ffe6cbaa870 r14: 00007ffe6cbaa878 r15: 00007ffe6cbaa3d0
  di: 0000000000003f8d  si: 0000000000003f8d  bp: 00007ffe6cbaa3c0  bx: 00007ffe6cbaa3d0
  dx: 0000000000000006  ax: 0000000000000000  cx: ffffffffffffffff  sp: 00007ffe6cbaa288
  ip: 00007ffa330d7c37 efl: 0000000000000206 cgf: 0000000000000033 erf: 0000000000000000
 trp: 0000000000000000 msk: 0000000000000000 cr2: 0000000000000000
[end of stack trace]

Example logs: https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.fyi%2FMojo_ChromiumOS%2F20776%2F%2B%2Frecipes%2Fsteps%2Fmash_browser_tests%2F0%2Fstdout