MediaRouterIntegrationOneUANoReceiverBrowserTest.ReconnectSessionSameTab failed in linux-chromeos-rel try-run on patch-set #3 of https://chromium-review.googlesource.com/c/chromium/src/+/989120, with:

[2882:2882:0401/155629.499108:FATAL:projecting_observer.cc(51)] Check failed: casting_session_count_ > 0 (0 vs. 0)
#0 0x000004347fdc base::debug::StackTrace::StackTrace()
#1 0x000004362e0b logging::LogMessage::~LogMessage()
#2 0x000007037116 ash::ProjectingObserver::OnCastingSessionStartedOrStopped()
#3 0x000006f86e36 ash::Shell::OnCastingSessionStartedOrStopped()
#4 0x00000450bdf5 MediaCaptureDevicesDispatcher::UpdateMediaRequestStateOnUIThread()
#5 0x00000450c71d _ZN4base8internal7InvokerINS0_9BindStateIM29MediaCaptureDevicesDispatcherFviiiRK4GURLN7content15MediaStreamTypeENS7_17MediaRequestStateEEJNS0_17UnretainedWrapperIS3_EEiiiS4_S8_S9_EEEFvvEE7RunOnceEPNS0_13BindStateBaseE
#6 0x0000043487b4 base::debug::TaskAnnotator::RunTask()
#7 0x000004401c89 base::internal::IncomingTaskQueue::RunTask()
#8 0x00000436b27b base::MessageLoop::RunTask()
#9 0x00000436b61a base::MessageLoop::DeferOrRunPendingTask()
#10 0x00000436b87c base::MessageLoop::DoWork()
#11 0x00000436d939 base::MessagePumpLibevent::Run()
#12 0x00000436aba9 base::MessageLoop::Run()
#13 0x000004395ab9 base::RunLoop::Run()
#14 0x0000049bc2e0 content::RunAllPendingInMessageLoop()
#15 0x00000445b4c1 InProcessBrowserTest::PostRunTestOnMainThread()
#16 0x0000049980e4 content::BrowserTestBase::ProxyRunTestOnMainThreadLoop()
#17 0x0000044a1e77 ChromeBrowserMainParts::PreMainMessageLoopRunImpl()
#18 0x0000044a0c2a ChromeBrowserMainParts::PreMainMessageLoopRun()
#19 0x000001a1f7a1 chromeos::ChromeBrowserMainPartsChromeos::PreMainMessageLoopRun()
#20 0x000002addce1 content::BrowserMainLoop::PreMainMessageLoopRun()
#21 0x000002f19995 content::StartupTaskRunner::RunAllTasksNow()
#22 0x000002adc762 content::BrowserMainLoop::CreateStartupTasks()
#23 0x000002ae07a3 content::BrowserMainRunnerImpl::Initialize()
#24 0x000002ada0b2 content::BrowserMain()
#25 0x0000042fec8d content::ContentMainRunnerImpl::Run()
#26 0x0000063da8e2 service_manager::Main()
#27 0x0000042fd304 content::ContentMain()
#28 0x000004997aab content::BrowserTestBase::SetUp()
#29 0x000004459f5e InProcessBrowserTest::SetUp()
#30 0x000001e91811 testing::Test::Run()
#31 0x000001e923d0 testing::TestInfo::Run()
#32 0x000001e928b7 testing::TestCase::Run()
#33 0x000001e9dda7 testing::internal::UnitTestImpl::RunAllTests()
#34 0x000001e9d92e testing::UnitTest::Run()
#35 0x00000446ea02 base::TestSuite::Run()
#36 0x00000433bb25 ChromeTestSuiteRunner::RunTestSuite()
#37 0x0000049b8877 content::LaunchTests()
#38 0x00000433bfe4 LaunchChromeTests()
#39 0x00000433babe main
#40 0x7fa491d91f45 __libc_start_main
#41 0x0000005d469a _start

[985/986] MediaRouterIntegrationOneUANoReceiverBrowserTest.ReconnectSessionSameTab (CRASHED)

Note that this appears to be a different failure from the one reported in  issue 826016 .