Version: 51.0.2687.0 git rev 9861e39f90174b134366db95471a64e0a474d874
OS: Windows 10.0.10586 on GCE

What steps will reproduce the problem?
(1) content_browsertests.exe --gtest_filter=BackgroundTracingManagerBrowserTest.* 

Seems to only fail on the GCE bot as I can't reproduce locally.

https://chromium-swarm-dev.appspot.com/user/task/2daf6576f3e90710

[ RUN      ] BackgroundTracingManagerBrowserTest.ReactiveTimeoutTermination

e:\b\build\slave\win\build\src\content\browser\tracing\background_tracing_manager_browsertest.cc(95): error: Value of: value
  Actual: false
Expected: expected
Which is: true
[224:3496:0321/011619:411718:FATAL:background_tracing_manager_impl.cc(386)] Check failed: tracing_timer_. 
Backtrace:
	base::debug::StackTrace::StackTrace [0x00007FF6B37871D1+33]
	logging::LogMessage::~LogMessage [0x00007FF6B371BD4C+76]
	content::BackgroundTracingManagerImpl::FireTimerForTesting [0x00007FF6B5B628CE+94]
	content::BackgroundTracingManagerBrowserTest_ReactiveTimeoutTermination_Test::RunTestOnMainThread [0x00007FF6B316A7CA+538]
	content::ContentBrowserTest::RunTestOnMainThreadLoop [0x00007FF6B349F433+179]
	content::BrowserTestBase::ProxyRunTestOnMainThreadLoop [0x00007FF6B349E475+261]
	content::ShellBrowserMainParts::PreMainMessageLoopRun [0x00007FF6B34D7DE8+264]
	content::BrowserMainLoop::PreMainMessageLoopRun [0x00007FF6B5ADCDB2+274]
	content::StartupTaskRunner::RunAllTasksNow [0x00007FF6B5C5ED0E+46]
	content::BrowserMainLoop::CreateStartupTasks [0x00007FF6B5ADA256+694]
	content::BrowserMainRunnerImpl::Initialize [0x00007FF6B5CBA840+928]
	ShellBrowserMain [0x00007FF6B60D8A6C+28]
	content::ShellMainDelegate::RunProcess [0x00007FF6B60D70C3+259]
	content::RunNamedProcessTypeMain [0x00007FF6B5FABBFF+255]
	content::ContentMainRunnerImpl::Run [0x00007FF6B5FABAAD+317]
	content::ContentMain [0x00007FF6B5FAAC70+48]
	content::BrowserTestBase::SetUp [0x00007FF6B349EE90+1600]
	content::ContentBrowserTest::SetUp [0x00007FF6B349F6B2+162]
	testing::Test::Run [0x00007FF6B3656CBF+143]
	testing::TestInfo::Run [0x00007FF6B36570EB+267]
	testing::TestCase::Run [0x00007FF6B3656EF4+308]
	testing::internal::UnitTestImpl::RunAllTests [0x00007FF6B365759E+670]
	testing::UnitTest::Run [0x00007FF6B36572BE+254]
	base::TestSuite::Run [0x00007FF6B60FBA8A+218]
	content::ContentTestLauncherDelegate::RunTestSuite [0x00007FF6B60D4AF9+57]
	content::LaunchTests [0x00007FF6B34ED4ED+685]
	main [0x00007FF6B60D4B74+68]
	__scrt_common_main_seh [0x00007FF6B6062790+292] (f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:264)
	BaseThreadInitThunk [0x00007FFF0C028102+34]
	RtlUserThreadStart [0x00007FFF0CF1C264+52]

[875/1310] BackgroundTracingManagerBrowserTest.ReactiveTimeoutTermination (388 ms)
[ RUN      ] BackgroundTracingManagerBrowserTest.ReceiveTraceSucceedsOnHigherHistogramSample

seems to be some kind of race