The |browser_context_| member of ExtensionMessageFilter is read in OnMessageReceived() on the IO thread but reset to null during shutdown on the UI thread. This is racy and causing browser tests to fail flakily on the TSan bots.

Example: https://chromium-swarm.appspot.com/task?id=3ea27d1191c6bf10

WARNING: ThreadSanitizer: data race (pid=21144)
  Write of size 8 at 0x7b240000cb90 by main thread:
    #0 extensions::ExtensionMessageFilter::ShutdownOnUIThread() extensions/browser/extension_message_filter.cc:83:20 (extensions_browsertests+0x1a7f335)
    #1 Invoke<void (extensions::ExtensionMessageFilter::*)(), extensions::ExtensionMessageFilter *> base/bind_internal.h:507:12 (extensions_browsertests+0x1a830f8)
    #2 MakeItSo<void (extensions::ExtensionMessageFilter::*const &)(), extensions::ExtensionMessageFilter *> base/bind_internal.h:607 (extensions_browsertests+0x1a830f8)
    #3 RunImpl<void (extensions::ExtensionMessageFilter::*const &)(), const std::__1::tuple<base::internal::UnretainedWrapper<extensions::ExtensionMessageFilter> > &, 0> base/bind_internal.h:680 (extensions_browsertests+0x1a830f8)
    #4 base::internal::Invoker<base::internal::BindState<void (extensions::ExtensionMessageFilter::*)(), base::internal::UnretainedWrapper<extensions::ExtensionMessageFilter> >, void ()>::Run(base::internal::BindStateBase*) base/bind_internal.h:662 (extensions_browsertests+0x1a830f8)
    #5 Run base/callback.h:129:12 (extensions_browsertests+0x66cedf6)
    #6 Notify<> base/callback_list.h:216 (extensions_browsertests+0x66cedf6)
    #7 KeyedServiceShutdownNotifier::Shutdown() components/keyed_service/core/keyed_service_shutdown_notifier.cc:19 (extensions_browsertests+0x66cedf6)
    #8 KeyedServiceFactory::ContextShutdown(base::SupportsUserData*) components/keyed_service/core/keyed_service_factory.cc:113:17 (extensions_browsertests+0x66ce474)
    #9 BrowserContextKeyedServiceFactory::BrowserContextShutdown(content::BrowserContext*) components/keyed_service/content/browser_context_keyed_service_factory.cc:84:24 (extensions_browsertests+0x66ca330)
    #10 BrowserContextKeyedServiceFactory::ContextShutdown(base::SupportsUserData*) components/keyed_service/content/browser_context_keyed_service_factory.cc:118:3 (extensions_browsertests+0x66ca4cc)
    #11 DependencyManager::DestroyContextServices(base::SupportsUserData*) components/keyed_service/core/dependency_manager.cc:91:14 (extensions_browsertests+0x66cb0de)
    #12 BrowserContextDependencyManager::DestroyBrowserContextServices(content::BrowserContext*) components/keyed_service/content/browser_context_dependency_manager.cc:52:22 (extensions_browsertests+0x66c9c40)
    #13 extensions::ShellBrowserMainParts::PostMainMessageLoopRun() extensions/shell/browser/shell_browser_main_parts.cc:287:51 (extensions_browsertests+0x44da79e)
    #14 content::BrowserMainLoop::ShutdownThreadsAndCleanUp() content/browser/browser_main_loop.cc:1056:13 (extensions_browsertests+0x2a96b7a)
    #15 content::BrowserMainRunnerImpl::Shutdown() content/browser/browser_main_runner_impl.cc:217:17 (extensions_browsertests+0x2a9a432)
    #16 content::BrowserMain(content::MainFunctionParams const&) content/browser/browser_main.cc:49:16 (extensions_browsertests+0x2a91a7d)
    #17 RunBrowserProcessMain content/app/content_main_runner_impl.cc:596:10 (extensions_browsertests+0x448e069)
    #18 content::ContentMainRunnerImpl::Run() content/app/content_main_runner_impl.cc:947 (extensions_browsertests+0x448e069)
    #19 content::ContentServiceManagerMainDelegate::RunEmbedderProcess() content/app/content_service_manager_main_delegate.cc:53:32 (extensions_browsertests+0x35960ff)
    #20 service_manager::Main(service_manager::MainParams const&) services/service_manager/embedder/main.cc:452:29 (extensions_browsertests+0x657007f)
    #21 content::ContentMain(content::ContentMainParams const&) content/app/content_main.cc:19:10 (extensions_browsertests+0x35973be)
    #22 content::BrowserTestBase::SetUp() content/public/test/browser_test_base.cc:330:3 (extensions_browsertests+0x6a6353a)
    #23 extensions::AppShellTest::SetUp() extensions/shell/test/shell_test.cc:47:29 (extensions_browsertests+0x1a430ec)
    #24 testing::Test::Run() third_party/googletest/src/googletest/src/gtest.cc (extensions_browsertests+0x357b6eb)
    #25 testing::TestInfo::Run() third_party/googletest/src/googletest/src/gtest.cc:2667:11 (extensions_browsertests+0x357c3ac)
    #26 testing::TestCase::Run() third_party/googletest/src/googletest/src/gtest.cc:2785:28 (extensions_browsertests+0x357cc36)
    #27 testing::internal::UnitTestImpl::RunAllTests() third_party/googletest/src/googletest/src/gtest.cc:5047:43 (extensions_browsertests+0x358d1d6)
    #28 testing::UnitTest::Run() third_party/googletest/src/googletest/src/gtest.cc (extensions_browsertests+0x358caba)
    #29 RUN_ALL_TESTS third_party/googletest/src/googletest/include/gtest/gtest.h:2329:46 (extensions_browsertests+0x6a76385)
    #30 base::TestSuite::Run() base/test/test_suite.cc:277 (extensions_browsertests+0x6a76385)
    #31 extensions::AppShellTestLauncherDelegate::RunTestSuite(int, char**) extensions/shell/test/shell_test_launcher_delegate.cc:15:38 (extensions_browsertests+0x1a43223)
    #32 content::LaunchTests(content::TestLauncherDelegate*, unsigned long, int, char**) content/public/test/test_launcher.cc:637:31 (extensions_browsertests+0x6a69d81)
    #33 main extensions/shell/test/shell_tests_main.cc:17:10 (extensions_browsertests+0x1a43471)

  Previous read of size 8 at 0x7b240000cb90 by thread T2:
    #0 extensions::ExtensionMessageFilter::OnMessageReceived(IPC::Message const&) extensions/browser/extension_message_filter.cc:122:8 (extensions_browsertests+0x1a7f7c4)
    #1 DispatchMessage content/public/browser/browser_message_filter.cc:93:24 (extensions_browsertests+0x28cf22d)
    #2 content::BrowserMessageFilter::Internal::OnMessageReceived(IPC::Message const&) content/public/browser/browser_message_filter.cc:73 (extensions_browsertests+0x28cf22d)
    #3 TryFiltersImpl ipc/message_filter_router.cc:22:21 (extensions_browsertests+0x4e04e00)
    #4 IPC::MessageFilterRouter::TryFilters(IPC::Message const&) ipc/message_filter_router.cc:87 (extensions_browsertests+0x4e04e00)
    #5 IPC::ChannelProxy::Context::TryFilters(IPC::Message const&) ipc/ipc_channel_proxy.cc:86:31 (extensions_browsertests+0x4df6974)
    #6 IPC::ChannelProxy::Context::OnMessageReceived(IPC::Message const&) ipc/ipc_channel_proxy.cc:121:8 (extensions_browsertests+0x4df6bc0)
    #7 IPC::ChannelMojo::OnMessageReceived(IPC::Message const&) ipc/ipc_channel_mojo.cc:263:14 (extensions_browsertests+0x4df2efc)
    #8 non-virtual thunk to IPC::ChannelMojo::OnMessageReceived(IPC::Message const&) ipc/ipc_channel_mojo.cc (extensions_browsertests+0x4df30b4)
    #9 IPC::internal::MessagePipeReader::Receive(base::span<unsigned char const, 18446744073709551615ul>, base::Optional<std::__1::vector<mojo::StructPtr<mojo::native::SerializedHandle>, std::__1::allocator<mojo::StructPtr<mojo::native::SerializedHandle> > > >) ipc/ipc_message_pipe_reader.cc:113:14 (extensions_browsertests+0x4dfb176)
    #10 IPC::mojom::ChannelStubDispatch::Accept(IPC::mojom::Channel*, mojo::Message*) gen/ipc/ipc.mojom.cc:289:13 (extensions_browsertests+0x4e05a5a)
    #11 IPC::mojom::ChannelStub<mojo::RawPtrImplRefTraits<IPC::mojom::Channel> >::Accept(mojo::Message*) gen/ipc/ipc.mojom.h:324:12 (extensions_browsertests+0x4dfb45f)
    #12 mojo::InterfaceEndpointClient::HandleValidatedMessage(mojo::Message*) mojo/public/cpp/bindings/lib/interface_endpoint_client.cc:419:32 (extensions_browsertests+0x45a5be1)
    #13 mojo::InterfaceEndpointClient::HandleIncomingMessageThunk::Accept(mojo::Message*) mojo/public/cpp/bindings/lib/interface_endpoint_client.cc:133:18 (extensions_browsertests+0x45a58ba)
    #14 mojo::FilterChain::Accept(mojo::Message*) mojo/public/cpp/bindings/lib/filter_chain.cc:40:17 (extensions_browsertests+0x45a807d)
    #15 mojo::InterfaceEndpointClient::HandleIncomingMessage(mojo::Message*) mojo/public/cpp/bindings/lib/interface_endpoint_client.cc:306:19 (extensions_browsertests+0x45a6e94)
    #16 IPC::(anonymous namespace)::ChannelAssociatedGroupController::Accept(mojo::Message*) ipc/ipc_mojo_bootstrap.cc:821:20 (extensions_browsertests+0x4dff946)
    #17 non-virtual thunk to IPC::(anonymous namespace)::ChannelAssociatedGroupController::Accept(mojo::Message*) ipc/ipc_mojo_bootstrap.cc (extensions_browsertests+0x4e000c4)
    #18 mojo::FilterChain::Accept(mojo::Message*) mojo/public/cpp/bindings/lib/filter_chain.cc:40:17 (extensions_browsertests+0x45a807d)
    #19 mojo::Connector::ReadSingleMessage(unsigned int*) mojo/public/cpp/bindings/lib/connector.cc:457:51 (extensions_browsertests+0x45a3c45)
    #20 mojo::Connector::ReadAllAvailableMessages() mojo/public/cpp/bindings/lib/connector.cc:486:10 (extensions_browsertests+0x45a46ea)
    #21 OnHandleReadyInternal mojo/public/cpp/bindings/lib/connector.cc:387:3 (extensions_browsertests+0x45a4575)
    #22 mojo::Connector::OnWatcherHandleReady(unsigned int) mojo/public/cpp/bindings/lib/connector.cc:364 (extensions_browsertests+0x45a4575)
    #23 Invoke<void (mojo::Connector::*)(unsigned int), mojo::Connector *, unsigned int> base/bind_internal.h:507:12 (extensions_browsertests+0x45a4c8f)
    #24 MakeItSo<void (mojo::Connector::*const &)(unsigned int), mojo::Connector *, unsigned int> base/bind_internal.h:607 (extensions_browsertests+0x45a4c8f)
    #25 RunImpl<void (mojo::Connector::*const &)(unsigned int), const std::__1::tuple<base::internal::UnretainedWrapper<mojo::Connector> > &, 0> base/bind_internal.h:680 (extensions_browsertests+0x45a4c8f)
    #26 base::internal::Invoker<base::internal::BindState<void (mojo::Connector::*)(unsigned int), base::internal::UnretainedWrapper<mojo::Connector> >, void (unsigned int)>::Run(base::internal::BindStateBase*, unsigned int) base/bind_internal.h:662 (extensions_browsertests+0x45a4c8f)
    #27 Run base/callback.h:129:12 (extensions_browsertests+0x27d2022)
    #28 mojo::SimpleWatcher::DiscardReadyState(base::RepeatingCallback<void (unsigned int)> const&, unsigned int, mojo::HandleSignalsState const&) mojo/public/cpp/system/simple_watcher.h:194 (extensions_browsertests+0x27d2022)
    #29 Invoke<void (*const &)(const base::RepeatingCallback<void (unsigned int)> &, unsigned int, const mojo::HandleSignalsState &), const base::RepeatingCallback<void (unsigned int)> &, unsigned int, const mojo::HandleSignalsState &> base/bind_internal.h:407:12 (extensions_browsertests+0x27d2065)
    #30 MakeItSo<void (*const &)(const base::RepeatingCallback<void (unsigned int)> &, unsigned int, const mojo::HandleSignalsState &), const base::RepeatingCallback<void (unsigned int)> &, unsigned int, const mojo::HandleSignalsState &> base/bind_internal.h:607 (extensions_browsertests+0x27d2065)
    #31 RunImpl<void (*const &)(const base::RepeatingCallback<void (unsigned int)> &, unsigned int, const mojo::HandleSignalsState &), const std::__1::tuple<base::RepeatingCallback<void (unsigned int)> > &, 0> base/bind_internal.h:680 (extensions_browsertests+0x27d2065)
    #32 base::internal::Invoker<base::internal::BindState<void (*)(base::RepeatingCallback<void (unsigned int)> const&, unsigned int, mojo::HandleSignalsState const&), base::RepeatingCallback<void (unsigned int)> >, void (unsigned int, mojo::HandleSignalsState const&)>::Run(base::internal::BindStateBase*, unsigned int, mojo::HandleSignalsState const&) base/bind_internal.h:662 (extensions_browsertests+0x27d2065)
    #33 Run base/callback.h:129:12 (extensions_browsertests+0x46e3d86)
    #34 mojo::SimpleWatcher::OnHandleReady(int, unsigned int, mojo::HandleSignalsState const&) mojo/public/cpp/system/simple_watcher.cc:274 (extensions_browsertests+0x46e3d86)
    #35 Invoke<void (mojo::SimpleWatcher::*)(int, unsigned int, const mojo::HandleSignalsState &), const base::WeakPtr<mojo::SimpleWatcher> &, const int &, const unsigned int &, const mojo::HandleSignalsState &> base/bind_internal.h:507:12 (extensions_browsertests+0x46e417c)
    #36 MakeItSo<void (mojo::SimpleWatcher::*const &)(int, unsigned int, const mojo::HandleSignalsState &), const base::WeakPtr<mojo::SimpleWatcher> &, const int &, const unsigned int &, const mojo::HandleSignalsState &> base/bind_internal.h:627 (extensions_browsertests+0x46e417c)
    #37 RunImpl<void (mojo::SimpleWatcher::*const &)(int, unsigned int, const mojo::HandleSignalsState &), const std::__1::tuple<base::WeakPtr<mojo::SimpleWatcher>, int, unsigned int, mojo::HandleSignalsState> &, 0, 1, 2, 3> base/bind_internal.h:680 (extensions_browsertests+0x46e417c)
    #38 base::internal::Invoker<base::internal::BindState<void (mojo::SimpleWatcher::*)(int, unsigned int, mojo::HandleSignalsState const&), base::WeakPtr<mojo::SimpleWatcher>, int, unsigned int, mojo::HandleSignalsState>, void ()>::Run(base::internal::BindStateBase*) base/bind_internal.h:662 (extensions_browsertests+0x46e417c)
    #39 Run base/callback.h:99:12 (extensions_browsertests+0x45f4ac7)
    #40 base::debug::TaskAnnotator::RunTask(char const*, base::PendingTask*) base/debug/task_annotator.cc:101 (extensions_browsertests+0x45f4ac7)
    #41 base::MessageLoop::RunTask(base::PendingTask*) base/message_loop/message_loop.cc:453:46 (extensions_browsertests+0x45f2735)
    #42 DeferOrRunPendingTask base/message_loop/message_loop.cc:464:5 (extensions_browsertests+0x45f30c8)
    #43 base::MessageLoop::DoWork() base/message_loop/message_loop.cc:522 (extensions_browsertests+0x45f30c8)
    #44 base::MessagePumpLibevent::Run(base::MessagePump::Delegate*) base/message_loop/message_pump_libevent.cc:210:31 (extensions_browsertests+0x46d4e04)
    #45 Run base/message_loop/message_loop.cc:405:12 (extensions_browsertests+0x45f2140)
    #46 non-virtual thunk to base::MessageLoop::Run(bool) base/message_loop/message_loop.cc (extensions_browsertests+0x45f2140)
    #47 base::RunLoop::Run() base/run_loop.cc:102:14 (extensions_browsertests+0x4622f1a)
    #48 base::Thread::Run(base::RunLoop*) base/threading/thread.cc:255:13 (extensions_browsertests+0x467da89)
    #49 content::BrowserProcessSubThread::IOThreadRun(base::RunLoop*) content/browser/browser_process_sub_thread.cc:178:11 (extensions_browsertests+0x2aa4176)
    #50 content::BrowserProcessSubThread::Run(base::RunLoop*) content/browser/browser_process_sub_thread.cc:128:7 (extensions_browsertests+0x2aa40d8)
    #51 base::Thread::ThreadMain() base/threading/thread.cc:337:3 (extensions_browsertests+0x467dcec)
    #52 base::(anonymous namespace)::ThreadFunc(void*) base/threading/platform_thread_posix.cc:76:13 (extensions_browsertests+0x46d093d)

  Location is heap block of size 136 at 0x7b240000cb10 allocated by main thread:
    #0 operator new(unsigned long) /b/swarming/w/ir/kitchen-workdir/src/third_party/llvm/compiler-rt/lib/tsan/rtl/tsan_new_delete.cc:65:3 (extensions_browsertests+0x19c46ed)
    #1 extensions::ShellContentBrowserClient::RenderProcessWillLaunch(content::RenderProcessHost*, mojo::InterfaceRequest<service_manager::mojom::Service>*) extensions/shell/browser/shell_content_browser_client.cc:105:7 (extensions_browsertests+0x44dab64)
    #2 content::RenderProcessHostImpl::Init() content/browser/renderer_host/render_process_host_impl.cc:1587:34 (extensions_browsertests+0x2f0c100)
    #3 InitRenderView content/browser/frame_host/render_frame_host_manager.cc:1912:40 (extensions_browsertests+0x2cce51c)
    #4 content::RenderFrameHostManager::ReinitializeRenderFrame(content::RenderFrameHostImpl*) content/browser/frame_host/render_frame_host_manager.cc:2063 (extensions_browsertests+0x2cce51c)
    #5 content::RenderFrameHostManager::GetFrameHostForNavigation(content::NavigationRequest const&) content/browser/frame_host/render_frame_host_manager.cc:637:10 (extensions_browsertests+0x2ccdc26)
    #6 content::RenderFrameHostManager::DidCreateNavigationRequest(content::NavigationRequest*) content/browser/frame_host/render_frame_host_manager.cc:488:35 (extensions_browsertests+0x2ccd4b3)
    #7 content::FrameTreeNode::CreatedNavigationRequest(std::__1::unique_ptr<content::NavigationRequest, std::__1::default_delete<content::NavigationRequest> >) content/browser/frame_host/frame_tree_node.cc:451:21 (extensions_browsertests+0x2c5e949)
    #8 content::NavigatorImpl::Navigate(std::__1::unique_ptr<content::NavigationRequest, std::__1::default_delete<content::NavigationRequest> >, content::ReloadType, content::RestoreType) content/browser/frame_host/navigator_impl.cc:382:20 (extensions_browsertests+0x2c90d72)
    #9 content::NavigationControllerImpl::NavigateWithoutEntry(content::NavigationController::LoadURLParams const&) content/browser/frame_host/navigation_controller_impl.cc:2403:22 (extensions_browsertests+0x2c68a72)
    #10 content::NavigationControllerImpl::LoadURLWithParams(content::NavigationController::LoadURLParams const&) content/browser/frame_host/navigation_controller_impl.cc:772:3 (extensions_browsertests+0x2c68210)
    #11 content::NavigationControllerImpl::LoadURL(GURL const&, content::Referrer const&, ui::PageTransition, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) content/browser/frame_host/navigation_controller_impl.cc:738:3 (extensions_browsertests+0x2c680ed)
    #12 extensions::ExtensionHost::LoadInitialURL() extensions/browser/extension_host.cc:210:35 (extensions_browsertests+0x1a7c5a9)
    #13 extensions::ExtensionHost::CreateRenderViewNow() extensions/browser/extension_host.cc:153:3 (extensions_browsertests+0x1a7be5a)
    #14 extensions::SerialExtensionHostQueue::ProcessOneHost() extensions/browser/serial_extension_host_queue.cc:79:19 (extensions_browsertests+0x1adac00)
    #15 Invoke<void (extensions::SerialExtensionHostQueue::*)(), const base::WeakPtr<extensions::SerialExtensionHostQueue> &> base/bind_internal.h:507:12 (extensions_browsertests+0x1adad4a)
    #16 MakeItSo<void (extensions::SerialExtensionHostQueue::*const &)(), const base::WeakPtr<extensions::SerialExtensionHostQueue> &> base/bind_internal.h:627 (extensions_browsertests+0x1adad4a)
    #17 RunImpl<void (extensions::SerialExtensionHostQueue::*const &)(), const std::__1::tuple<base::WeakPtr<extensions::SerialExtensionHostQueue> > &, 0> base/bind_internal.h:680 (extensions_browsertests+0x1adad4a)
    #18 base::internal::Invoker<base::internal::BindState<void (extensions::SerialExtensionHostQueue::*)(), base::WeakPtr<extensions::SerialExtensionHostQueue> >, void ()>::Run(base::internal::BindStateBase*) base/bind_internal.h:662 (extensions_browsertests+0x1adad4a)
    #19 Run base/callback.h:99:12 (extensions_browsertests+0x45f4ac7)
    #20 base::debug::TaskAnnotator::RunTask(char const*, base::PendingTask*) base/debug/task_annotator.cc:101 (extensions_browsertests+0x45f4ac7)
    #21 base::MessageLoop::RunTask(base::PendingTask*) base/message_loop/message_loop.cc:453:46 (extensions_browsertests+0x45f2735)
    #22 DeferOrRunPendingTask base/message_loop/message_loop.cc:464:5 (extensions_browsertests+0x45f30c8)
    #23 base::MessageLoop::DoWork() base/message_loop/message_loop.cc:522 (extensions_browsertests+0x45f30c8)
    #24 HandleDispatch base/message_loop/message_pump_glib.cc:263:25 (extensions_browsertests+0x45f8a57)
    #25 base::(anonymous namespace)::WorkSourceDispatch(_GSource*, int (*)(void*), void*) base/message_loop/message_pump_glib.cc:109 (extensions_browsertests+0x45f8a57)
    #26 g_main_context_dispatch <null> (libglib-2.0.so.0+0x48e03)
    #27 Run base/message_loop/message_loop.cc:405:12 (extensions_browsertests+0x45f2140)
    #28 non-virtual thunk to base::MessageLoop::Run(bool) base/message_loop/message_loop.cc (extensions_browsertests+0x45f2140)
    #29 base::RunLoop::Run() base/run_loop.cc:102:14 (extensions_browsertests+0x4622f1a)
    #30 ExtensionTestMessageListener::WaitUntilSatisfied() extensions/test/extension_test_message_listener.cc:48:12 (extensions_browsertests+0x968a594)
    #31 extensions::UsbApiTest_GetUserSelectedDevices_Test::RunTestOnMainThread() extensions/browser/api/usb/usb_apitest.cc:296:3 (extensions_browsertests+0x1a1794c)
    #32 content::BrowserTestBase::ProxyRunTestOnMainThreadLoop() content/public/test/browser_test_base.cc:414:5 (extensions_browsertests+0x6a63a4a)
    #33 Invoke<void (content::BrowserTestBase::*)(), content::BrowserTestBase *> base/bind_internal.h:507:12 (extensions_browsertests+0x6a644b8)
    #34 MakeItSo<void (content::BrowserTestBase::*const &)(), content::BrowserTestBase *> base/bind_internal.h:607 (extensions_browsertests+0x6a644b8)
    #35 RunImpl<void (content::BrowserTestBase::*const &)(), const std::__1::tuple<base::internal::UnretainedWrapper<content::BrowserTestBase> > &, 0> base/bind_internal.h:680 (extensions_browsertests+0x6a644b8)
    #36 base::internal::Invoker<base::internal::BindState<void (content::BrowserTestBase::*)(), base::internal::UnretainedWrapper<content::BrowserTestBase> >, void ()>::Run(base::internal::BindStateBase*) base/bind_internal.h:662 (extensions_browsertests+0x6a644b8)
    #37 Run base/callback.h:129:12 (extensions_browsertests+0x44da604)
    #38 extensions::ShellBrowserMainParts::PreMainMessageLoopRun() extensions/shell/browser/shell_browser_main_parts.cc:258 (extensions_browsertests+0x44da604)
    #39 content::BrowserMainLoop::PreMainMessageLoopRun() content/browser/browser_main_loop.cc:1006:13 (extensions_browsertests+0x2a96550)
    #40 Invoke<int (content::BrowserMainLoop::*)(), content::BrowserMainLoop *> base/bind_internal.h:507:12 (extensions_browsertests+0x2a99698)
    #41 MakeItSo<int (content::BrowserMainLoop::*const &)(), content::BrowserMainLoop *> base/bind_internal.h:607 (extensions_browsertests+0x2a99698)
    #42 RunImpl<int (content::BrowserMainLoop::*const &)(), const std::__1::tuple<base::internal::UnretainedWrapper<content::BrowserMainLoop> > &, 0> base/bind_internal.h:680 (extensions_browsertests+0x2a99698)
    #43 base::internal::Invoker<base::internal::BindState<int (content::BrowserMainLoop::*)(), base::internal::UnretainedWrapper<content::BrowserMainLoop> >, int ()>::Run(base::internal::BindStateBase*) base/bind_internal.h:662 (extensions_browsertests+0x2a99698)
    #44 Run base/callback.h:129:12 (extensions_browsertests+0x30873fe)
    #45 content::StartupTaskRunner::RunAllTasksNow() content/browser/startup_task_runner.cc:43 (extensions_browsertests+0x30873fe)
    #46 content::BrowserMainLoop::CreateStartupTasks() content/browser/browser_main_loop.cc:917:25 (extensions_browsertests+0x2a94794)
    #47 content::BrowserMainRunnerImpl::Initialize(content::MainFunctionParams const&) content/browser/browser_main_runner_impl.cc:141:15 (extensions_browsertests+0x2a99c2a)
    #48 content::BrowserMain(content::MainFunctionParams const&) content/browser/browser_main.cc:43:32 (extensions_browsertests+0x2a91a4a)
    #49 RunBrowserProcessMain content/app/content_main_runner_impl.cc:596:10 (extensions_browsertests+0x448e069)
    #50 content::ContentMainRunnerImpl::Run() content/app/content_main_runner_impl.cc:947 (extensions_browsertests+0x448e069)
    #51 content::ContentServiceManagerMainDelegate::RunEmbedderProcess() content/app/content_service_manager_main_delegate.cc:53:32 (extensions_browsertests+0x35960ff)
    #52 service_manager::Main(service_manager::MainParams const&) services/service_manager/embedder/main.cc:452:29 (extensions_browsertests+0x657007f)
    #53 content::ContentMain(content::ContentMainParams const&) content/app/content_main.cc:19:10 (extensions_browsertests+0x35973be)
    #54 content::BrowserTestBase::SetUp() content/public/test/browser_test_base.cc:330:3 (extensions_browsertests+0x6a6353a)
    #55 extensions::AppShellTest::SetUp() extensions/shell/test/shell_test.cc:47:29 (extensions_browsertests+0x1a430ec)
    #56 testing::Test::Run() third_party/googletest/src/googletest/src/gtest.cc (extensions_browsertests+0x357b6eb)
    #57 testing::TestInfo::Run() third_party/googletest/src/googletest/src/gtest.cc:2667:11 (extensions_browsertests+0x357c3ac)
    #58 testing::TestCase::Run() third_party/googletest/src/googletest/src/gtest.cc:2785:28 (extensions_browsertests+0x357cc36)
    #59 testing::internal::UnitTestImpl::RunAllTests() third_party/googletest/src/googletest/src/gtest.cc:5047:43 (extensions_browsertests+0x358d1d6)
    #60 testing::UnitTest::Run() third_party/googletest/src/googletest/src/gtest.cc (extensions_browsertests+0x358caba)
    #61 RUN_ALL_TESTS third_party/googletest/src/googletest/include/gtest/gtest.h:2329:46 (extensions_browsertests+0x6a76385)
    #62 base::TestSuite::Run() base/test/test_suite.cc:277 (extensions_browsertests+0x6a76385)
    #63 extensions::AppShellTestLauncherDelegate::RunTestSuite(int, char**) extensions/shell/test/shell_test_launcher_delegate.cc:15:38 (extensions_browsertests+0x1a43223)
    #64 content::LaunchTests(content::TestLauncherDelegate*, unsigned long, int, char**) content/public/test/test_launcher.cc:637:31 (extensions_browsertests+0x6a69d81)
    #65 main extensions/shell/test/shell_tests_main.cc:17:10 (extensions_browsertests+0x1a43471)

  Thread T2 'Chrome_IOThread' (tid=21156, running) created by main thread at:
    #0 pthread_create /b/swarming/w/ir/kitchen-workdir/src/third_party/llvm/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:965:3 (extensions_browsertests+0x195a725)
    #1 base::(anonymous namespace)::CreateThread(unsigned long, bool, base::PlatformThread::Delegate*, base::PlatformThreadHandle*, base::ThreadPriority) base/threading/platform_thread_posix.cc:115:13 (extensions_browsertests+0x46d04c7)
    #2 base::PlatformThread::CreateWithPriority(unsigned long, base::PlatformThread::Delegate*, base::PlatformThreadHandle*, base::ThreadPriority) base/threading/platform_thread_posix.cc:200:10 (extensions_browsertests+0x46d03c5)
    #3 base::Thread::StartWithOptions(base::Thread::Options const&) base/threading/thread.cc:112:15 (extensions_browsertests+0x467d5ae)
    #4 content::BrowserProcessSubThread::CreateIOThread() content/browser/browser_process_sub_thread.cc:91:19 (extensions_browsertests+0x2aa3eee)
    #5 content::ContentMainRunnerImpl::Run() content/app/content_main_runner_impl.cc:927:29 (extensions_browsertests+0x448de85)
    #6 content::ContentServiceManagerMainDelegate::RunEmbedderProcess() content/app/content_service_manager_main_delegate.cc:53:32 (extensions_browsertests+0x35960ff)
    #7 service_manager::Main(service_manager::MainParams const&) services/service_manager/embedder/main.cc:452:29 (extensions_browsertests+0x657007f)
    #8 content::ContentMain(content::ContentMainParams const&) content/app/content_main.cc:19:10 (extensions_browsertests+0x35973be)
    #9 content::BrowserTestBase::SetUp() content/public/test/browser_test_base.cc:330:3 (extensions_browsertests+0x6a6353a)
    #10 extensions::AppShellTest::SetUp() extensions/shell/test/shell_test.cc:47:29 (extensions_browsertests+0x1a430ec)
    #11 testing::Test::Run() third_party/googletest/src/googletest/src/gtest.cc (extensions_browsertests+0x357b6eb)
    #12 testing::TestInfo::Run() third_party/googletest/src/googletest/src/gtest.cc:2667:11 (extensions_browsertests+0x357c3ac)
    #13 testing::TestCase::Run() third_party/googletest/src/googletest/src/gtest.cc:2785:28 (extensions_browsertests+0x357cc36)
    #14 testing::internal::UnitTestImpl::RunAllTests() third_party/googletest/src/googletest/src/gtest.cc:5047:43 (extensions_browsertests+0x358d1d6)
    #15 testing::UnitTest::Run() third_party/googletest/src/googletest/src/gtest.cc (extensions_browsertests+0x358caba)
    #16 RUN_ALL_TESTS third_party/googletest/src/googletest/include/gtest/gtest.h:2329:46 (extensions_browsertests+0x6a76385)
    #17 base::TestSuite::Run() base/test/test_suite.cc:277 (extensions_browsertests+0x6a76385)
    #18 extensions::AppShellTestLauncherDelegate::RunTestSuite(int, char**) extensions/shell/test/shell_test_launcher_delegate.cc:15:38 (extensions_browsertests+0x1a43223)
    #19 content::LaunchTests(content::TestLauncherDelegate*, unsigned long, int, char**) content/public/test/test_launcher.cc:637:31 (extensions_browsertests+0x6a69d81)
    #20 main extensions/shell/test/shell_tests_main.cc:17:10 (extensions_browsertests+0x1a43471)

SUMMARY: ThreadSanitizer: data race extensions/browser/extension_message_filter.cc:83:20 in extensions::ExtensionMessageFilter::ShutdownOnUIThread()