I see two types of failures. One is because we're trying to create multiple UICursorFactoryOzones (filed at  bug 916180 ), the other looks to be because a connection is getting closed unexpectedly. This most likely indicates we need test_ws running. Here's output:

#0 0x55abe00d648f base::debug::StackTrace::StackTrace()
#1 0x55abe003e68b logging::LogMessage::~LogMessage()
#2 0x55abe17d2088 cc::mojo_embedder::AsyncLayerTreeFrameSink::OnMojoConnectionError()
#3 0x55abdd9f53fc _ZN4base8internal7InvokerINS0_9BindStateIMN8download16DownloadItemImplEFvNS3_23DownloadInterruptReasonERKNS_8FilePathEEJNS_7WeakPtrIS4_EEEEEFvS5_S8_EE3RunEPNS0_13BindStateBaseES5_S8_
#4 0x55abdfd21c59 mojo::InterfaceEndpointClient::NotifyError()
#5 0x55abdfd27d97 mojo::internal::MultiplexRouter::ProcessNotifyErrorTask()
#6 0x55abdfd24ebb mojo::internal::MultiplexRouter::ProcessTasks()
#7 0x55abdfd2690e mojo::internal::MultiplexRouter::Accept()
#8 0x55abdfd20336 mojo::FilterChain::Accept()
#9 0x55abdfd1e379 mojo::Connector::ReadSingleMessage()
#10 0x55abdfd1ed71 mojo::Connector::ReadAllAvailableMessages()
#11 0x55abdfd1ec19 mojo::Connector::OnHandleReadyInternal()
#12 0x55abdda09107 mojo::SimpleWatcher::DiscardReadyState()
#13 0x55abe011d442 mojo::SimpleWatcher::OnHandleReady()
#14 0x55abde50f231 _ZN4base8internal7InvokerINS0_9BindStateIMN3viz14GpuServiceImplEFvN3gfx21GenericSharedMemoryIdEiRKN3gpu9SyncTokenEEJNS_7WeakPtrIS4_EES6_iS8_EEEFvvEE7RunImplISC_NSt3__15tupleIJSE_S6_iS8_EEEJLm0ELm1ELm2ELm3EEEEvOT_OT0_NSJ_16integer_sequenceImJXspT1_EEEE
#15 0x55abe00f87c1 base::debug::TaskAnnotator::RunTask()
#16 0x55abe00491f0 base::MessageLoopImpl::RunTask()
#17 0x55abe00497e3 base::MessageLoopImpl::DoWork()
#18 0x55abe00f32d9 base::MessagePumpLibevent::Run()
#19 0x55abe0048d98 base::MessageLoopImpl::Run()
#20 0x55abe00699c9 base::RunLoop::Run()
#21 0x55abdd653b3d content::(anonymous namespace)::AuraWindowVideoCaptureDeviceBrowserTest::WaitForFrameWithColor()
#22 0x55abdd646dcf content::ContentCaptureDeviceBrowserTestBase::AllocateAndStartAndWaitForFirstFrame()
#23 0x55abdd653f77 content::(anonymous namespace)::AuraWindowVideoCaptureDeviceBrowserTest_DeliversRefreshFramesUponRequest_Test::RunTestOnMainThread()
#24 0x55abdfc58779 content::BrowserTestBase::ProxyRunTestOnMainThreadLoop()
#25 0x55abdfcd6269 content::ShellBrowserMainParts::PreMainMessageLoopRun()
#26 0x55abdf491ad2 content::BrowserMainLoop::PreMainMessageLoopRun()
#27 0x55abdf94dcc5 content::StartupTaskRunner::RunAllTasksNow()
#28 0x55abdf4907b5 content::BrowserMainLoop::CreateStartupTasks()
#29 0x55abdf493bf9 content::BrowserMainRunnerImpl::Initialize()
#30 0x55abdfcb1c5d ShellBrowserMain()
#31 0x55abdfcaf180 content::ShellMainDelegate::RunProcess()
#32 0x55abdf38b6b8 content::ContentMainRunnerImpl::RunServiceManager()
#33 0x55abdf38b2f4 content::ContentMainRunnerImpl::Run()
#34 0x55abe1829749 service_manager::Main()
#35 0x55abde5ba7e4 content::ContentMain()
#36 0x55abdfc5836c content::BrowserTestBase::SetUp()
#37 0x55abde230cf0 testing::Test::Run()
#38 0x55abde231a8f testing::TestInfo::Run()
#39 0x55abde231fb7 testing::TestCase::Run()
#40 0x55abde23e1f7 testing::internal::UnitTestImpl::RunAllTests()
#41 0x55abde23dd6d testing::UnitTest::Run()
#42 0x55abdfc8fce1 base::TestSuite::Run()
#43 0x55abdfc5008a content::ContentTestLauncherDelegate::RunTestSuite()
#44 0x55abdfc76bba content::LaunchTests()
#45 0x55abdfc50050 main
#46 0x7f17b734ff45 __libc_start_main
#47 0x55abdd013a8a _start

You can see this if you change the default for the SingleProcessMash feature flag to ENABLED_BY_DEFAULT.