This is hitting:

@bmcquade: any idea? Looks like you most recently touched CorePageLoadMetricsObserver.

[4464:2680:0515/232517.791:FATAL:optional.h(219)] Check failed: !storage_.is_null_.
Backtrace:
	base::debug::StackTrace::StackTrace [0x028FADB7+55]
	base::debug::StackTrace::StackTrace [0x028C15FA+10]
	base::Optional<unsigned __int64>::value [0x03FCAC8C+78]
	CorePageLoadMetricsObserver::OnFirstContentfulPaintInPage [0x03F6895F+303]
	page_load_metrics::PageLoadTracker::DidFinishSubFrameNavigation [0x03F6CC35+490]
	page_load_metrics::PageLoadTracker::UpdateSubFrameTiming [0x03F6E39E+242]
	page_load_metrics::MetricsWebContentsObserver::OnTimingUpdated [0x03F66308+152]
	IPC::DispatchToMethodImpl<page_load_metrics::MetricsWebContentsObserver,void (__thiscall page_load_metrics::MetricsWebContentsObserver::*)(content::RenderFrameHost *,page_load_metrics::PageLoadTiming const &,page_load_metrics::PageLoadMetadata const &),co [0x03F65175+23]
	??$DispatchToMethod@VMetricsWebContentsObserver@page_load_metrics@@VRenderFrameHost@content@@ABUPageLoadTiming@2@ABUPageLoadMetadata@2@$$ZU52@U62@@IPC@@YAXPAVMetricsWebContentsObserver@page_load_metrics@@P812@AEXPAVRenderFrameHost@content@@ABUPageLoadTimi [0x03F65157+27]
	IPC::MessageT<PageLoadMetricsMsg_TimingUpdated_Meta,std::tuple<page_load_metrics::PageLoadTiming,page_load_metrics::PageLoadMetadata>,void>::Dispatch<page_load_metrics::MetricsWebContentsObserver,page_load_metrics::MetricsWebContentsObserver,content::Rend [0x03F6511C+200]
	page_load_metrics::MetricsWebContentsObserver::OnMessageReceived [0x03F660B3+275]
	content::WebContentsImpl::OnMessageReceived [0x01E8AFD9+89]
	content::RenderFrameHostImpl::OnMessageReceived [0x01CBCDA4+164]
	content::RenderProcessHostImpl::OnMessageReceived [0x01DDEFEB+795]
	IPC::ChannelProxy::Context::OnDispatchMessage [0x031FE8ED+29]
	base::internal::Invoker<base::internal::BindState<base::internal::IgnoreResultHelper<bool (__thiscall content::BrowserMessageFilter::Internal::*)(IPC::Message const &)>,scoped_refptr<content::BrowserMessageFilter::Internal>,IPC::Message>,void __cdecl(void [0x031FED70+32]
	base::debug::TaskAnnotator::RunTask [0x028FE8B9+409]
	base::MessageLoop::RunTask [0x028837A9+1225]
	base::MessageLoop::DoWork [0x02882BD2+738]
	base::MessagePumpForUI::DoRunLoop [0x028FFB7D+93]
	base::MessagePumpWin::Run [0x0290030A+74]
	base::MessageLoop::RunHandler [0x028832CF+175]
	base::RunLoop::Run [0x0287FEE4+132]
	content::RunThisRunLoop [0x029DAC4A+27]
	extensions::ResultCatcher::GetNextResult [0x04DC7008+73]
	ExtensionApiTest::RunExtensionTestImpl [0x0172C828+819]
	ExtensionApiTest::RunExtensionSubtest [0x0172C44B+112]
	ExtensionApiTest::RunExtensionSubtest [0x0172C3D7+16]
	DestructiveScriptTest::RunSubtest [0x0138760C+180]
	DestructiveScriptTest_MacrotaskRemoval_Test::RunTestOnMainThread [0x01387C15+48]
	content::BrowserTestBase::ProxyRunTestOnMainThreadLoop [0x029E28E9+233]
	ChromeBrowserMainParts::PreMainMessageLoopRunImpl [0x03134CF7+3320]
	ChromeBrowserMainParts::PreMainMessageLoopRun [0x03133FC7+167]
	content::BrowserMainLoop::PreMainMessageLoopRun [0x01C02580+112]
	content::StartupTaskRunner::RunAllTasksNow [0x01E684A2+35]
	content::BrowserMainLoop::CreateStartupTasks [0x01C0051F+394]
	content::BrowserMainRunnerImpl::Initialize [0x01C037D0+704]
	content::BrowserMain [0x01BFF2A5+117]
	content::RunNamedProcessTypeMain [0x0285BDCC+206]
	content::ContentMainRunnerImpl::Run [0x0285BCCD+413]
	service_manager::Main [0x037CAF86+524]
	content::ContentMain [0x0285B379+39]
	content::BrowserTestBase::SetUp [0x029E2E12+866]
	InProcessBrowserTest::SetUp [0x0292C3D6+310]
	testing::internal::HandleExceptionsInMethodIfSupported<testing::TestCase,void> [0x01857F7D+32]
	testing::Test::Run [0x0185F15F+51]
	testing::TestCase::Run [0x0185F235+133]
	testing::internal::UnitTestImpl::RunAllTests [0x0185F5C1+433]
	testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl,bool> [0x01857FC1+32]
	testing::UnitTest::Run [0x0185F3DE+133]
	base::TestSuite::Run [0x0293BFF6+95]
	ChromeTestSuiteRunner::RunTestSuite [0x04E4C3E8+40]
	content::LaunchTests [0x029DB9F0+583]
	LaunchChromeTests [0x04E4C3A4+62]
	main [0x04E4C1B9+63]
	__scrt_common_main_seh [0x04DFBDFB+249] (f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:253)
	BaseThreadInitThunk [0x76A5337A+18]
	RtlInitializeExceptionChain [0x77389882+99]
	RtlInitializeExceptionChain [0x77389855+54]

This was actually caused by zhenw's change https://codereview.chromium.org/2872793002 which has been rolled back. We're working on a fix but if you sync to ToT you should be ok.

Removing sheriff label since the change was rolled back, thanks

This should be resolved. Closing.