SAMLPolicyTest.PRE_TransferCookiesAffiliated flake in single_process_mash_browser_tests on linux-chromeos-dbg

I only observed one failure so far, and the flakiness dashboards don't actually link to other failures, so this is low priority for now.
 https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/linux-chromeos-dbg/9183
 https://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=PRE_TransferCookiesAffiliated

[519/519] SAMLPolicyTest.PRE_TransferCookiesAffiliated (CRASHED)
[1126/210919.101762:FATAL:test_results_tracker.cc(513)] Check failed: location_it != test_locations_.end(). SAMLPolicyTest.PRE_TransferCookiesAffiliated
#0 0x7f026cc9fbfd base::debug::StackTrace::StackTrace()
#1 0x7f026c99ba7a base::debug::StackTrace::StackTrace()
#2 0x7f026ca07bfe logging::LogMessage::~LogMessage()
#3 0x55e0b695f558 base::TestResultsTracker::PrintTests<>()
#4 0x55e0b6956659 base::TestResultsTracker::PrintSummaryOfCurrentIteration()
#5 0x55e0b6943a6f base::TestLauncher::OnTestIterationFinished()
#6 0x55e0b6942836 base::TestLauncher::OnTestFinished()
#7 0x55e0b7d83323 content::(anonymous namespace)::WrapperTestLauncherDelegate::GTestCallback()
#8 0x55e0b7d8253a content::(anonymous namespace)::WrapperTestLauncherDelegate::ChildProcessLifetimeObserver::OnCompleted()
#9 0x55e0b694d6c0 _ZN4base8internal13FunctorTraitsIMNS_23ProcessLifetimeObserverEFviNS_9TimeDeltaEbRKNSt3__112basic_stringIcNS4_11char_traitsIcEENS4_9allocatorIcEEEEEvE6InvokeISE_NS4_10unique_ptrIS2_NS4_14default_deleteIS2_EEEEJiS3_bSA_EEEvT_OT0_DpOT1_
#10 0x55e0b694d591 _ZN4base8internal12InvokeHelperILb0EvE8MakeItSoIMNS_23ProcessLifetimeObserverEFviNS_9TimeDeltaEbRKNSt3__112basic_stringIcNS6_11char_traitsIcEENS6_9allocatorIcEEEEEJNS6_10unique_ptrIS4_NS6_14default_deleteIS4_EEEEiS5_bSC_EEEvOT_DpOT0_
#11 0x55e0b694d4dd _ZN4base8internal7InvokerINS0_9BindStateIMNS_23ProcessLifetimeObserverEFviNS_9TimeDeltaEbRKNSt3__112basic_stringIcNS5_11char_traitsIcEENS5_9allocatorIcEEEEEJNS5_10unique_ptrIS3_NS5_14default_deleteIS3_EEEEiS4_bSB_EEEFvvEE7RunImplISF_NS5_5tupleIJSJ_iS4_bSB_EEEJLm0ELm1ELm2ELm3ELm4EEEEvOT_OT0_NS5_16integer_sequenceImJXspT1_EEEE
#12 0x55e0b694d2c9 _ZN4base8internal7InvokerINS0_9BindStateIMNS_23ProcessLifetimeObserverEFviNS_9TimeDeltaEbRKNSt3__112basic_stringIcNS5_11char_traitsIcEENS5_9allocatorIcEEEEEJNS5_10unique_ptrIS3_NS5_14default_deleteIS3_EEEEiS4_bSB_EEEFvvEE7RunOnceEPNS0_13BindStateBaseE
#13 0x7f026c94d69e _ZNO4base12OnceCallbackIFvvEE3RunEv
#14 0x7f026c99cf2a base::debug::TaskAnnotator::RunTask()
#15 0x7f026ca2df6c base::MessageLoopImpl::RunTask()
#16 0x7f026ca2e26b base::MessageLoopImpl::DeferOrRunPendingTask()
#17 0x7f026ca2eaa4 base::MessageLoopImpl::DoWork()
#18 0x7f026ccf2d39 base::MessagePumpLibevent::Run()
#19 0x7f026ca2d786 base::MessageLoopImpl::Run()
#20 0x7f026cad8ed2 base::RunLoop::Run()
#21 0x55e0b6938bbd base::TestLauncher::Run()
#22 0x55e0b7d7b865 content::LaunchTests()
#23 0x55e0b67c1302 LaunchChromeTests()
#24 0x55e0b67bf80b main
#25 0x7f0239b93f45 __libc_start_main
#26 0x55e0af21bc0a _start