linux-chromeos-rel build
run ash_unittests locally

[ RUN      ] TouchAccessibilityEnablerTest.InteractsWithTouchExplorationController
[97361:97361:0517/172328.685345:14533058810:FATAL:screen_ash.cc(73)] Check failed: false. Observer should not be added during shutdown
#0 0x7ff3069badcc base::debug::StackTrace::StackTrace()
#1 0x7ff30690286b logging::LogMessage::~LogMessage()
#2 0x7ff306decf30 ash::(anonymous namespace)::ScreenForShutdown::AddObserver()
#3 0x7ff305325bdd aura::WindowTreeHost::WindowTreeHost()
#4 0x7ff305326b26 aura::WindowTreeHostPlatform::WindowTreeHostPlatform()
#5 0x7ff305326af2 aura::WindowTreeHost::Create()
#6 0x000000d391d3 aura::TestScreen::CreateHostForPrimaryDisplay()
#7 0x000000d35b03 aura::test::AuraTestHelper::SetUp()
#8 0x000000d349c2 aura::test::AuraTestBase::SetUp()
#9 0x0000005cae2f ash::(anonymous namespace)::TouchAccessibilityEnablerTest::SetUp()
#10 0x000000c2cead testing::Test::Run()
#11 0x000000c2d9f0 testing::TestInfo::Run()
#12 0x000000c2df07 testing::TestCase::Run()
#13 0x000000c39507 testing::internal::UnitTestImpl::RunAllTests()
#14 0x000000c3907d testing::UnitTest::Run()
#15 0x000000d169c1 base::TestSuite::Run()
#16 0x000000d18990 base::(anonymous namespace)::LaunchUnitTestsInternal()
#17 0x000000d187f0 base::LaunchUnitTests()
#18 0x0000009e6993 main
#19 0x7ff3024d22b1 __libc_start_main
#20 0x00000058b03a _start

This is because ScreenForShutdown is persisted between tests.

There is probably similar flake in chrome's unit_tests suite, which mixes AshTestBase tests with other tests.