Seems to have been timing out regularly since 10/20, for example from https://build.chromium.org/p/chromium.linux/builders/Linux%20Tests%20(dbg)(1)/builds/67922

[ RUN      ] SignalSenderVerificationTest.TestOwnerStealing
../../dbus/signal_sender_verification_unittest.cc:90: Failure
Value of: test_service2_->WaitUntilServiceIsStarted()
  Actual: false
Expected: true
[31305:31305:1101/142531.992120:24956091325:ERROR:bus.cc(506)] Failed to shutdown the bus
[31305:31439:1101/142534.992578:24959091797:ERROR:bus.cc(506)] Failed to shutdown the bus
[31305:31437:1101/142534.992587:24959091803:ERROR:bus.cc(506)] Failed to shutdown the bus
[ RUN      ] SignalSenderVerificationTest.TestOwnerStealing
[ RUN      ] SignalSenderVerificationTest.TestOwnerStealing
[31611:31612:1101/143255.635136:25399734337:ERROR:bus.cc(552)] Failed to get the ownership of org.chromium.TestService-c9d63aa0-9a65-4717-a0cf-7f37419ea408:
[31611:31616:1101/143255.635245:25399734445:ERROR:test_service.cc(150)] Failed to own: org.chromium.TestService-c9d63aa0-9a65-4717-a0cf-7f37419ea408
[ RUN      ] SignalSenderVerificationTest.TestOwnerStealing
[31622:31623:1101/143340.655730:25444754930:ERROR:bus.cc(552)] Failed to get the ownership of org.chromium.TestService-cf43c943-0f6a-4ecd-8233-e501af9df6e9:
[31622:31627:1101/143340.655827:25444755025:ERROR:test_service.cc(150)] Failed to own: org.chromium.TestService-cf43c943-0f6a-4ecd-8233-e501af9df6e9

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=dbus_unittests&tests=SignalSenderVerificationTest.TestOwnerStealing

Also we've seen one crash, see https://uberchromegw.corp.google.com/i/chromium.linux/builders/Linux%20Tests%20%28dbg%29%281%29/builds/67944

[ RUN      ] SignalSenderVerificationTest.TestOwnerStealing
[16820:16995:1102/103010.179720:11014201158:ERROR:bus.cc(552)] Failed to get the ownership of org.chromium.TestService-8323a15a-10a0-44ae-ab31-83b27e10d9ef:
[16820:16999:1102/103010.179800:11014201238:ERROR:test_service.cc(150)] Failed to own: org.chromium.TestService-8323a15a-10a0-44ae-ab31-83b27e10d9ef
../../dbus/signal_sender_verification_unittest.cc:279: Failure
Value of: stealable_test_service.WaitUntilServiceIsStarted()
  Actual: false
Expected: true
[16820:16820:1102/103055.181245:11059202682:FATAL:thread_restrictions.cc(29)] Check failed: !g_blocking_disallowed.Get().Get(). Function marked as blocking was called from a scope that disallows blocking! If this task is running inside the TaskScheduler, it needs to have MayBlock() in its TaskTraits. Otherwise, consider making this blocking work asynchronous or, as a last resort, you may use ScopedAllowBlocking in a narrow scope.
#0 0x7fba0e774f2d base::debug::StackTrace::StackTrace()
#1 0x7fba0e77335c base::debug::StackTrace::StackTrace()
#2 0x7fba0e7fa2aa logging::LogMessage::~LogMessage()
#3 0x7fba0e994bd7 base::AssertBlockingAllowed()
#4 0x7fba0e975dba base::PlatformThread::Join()
#5 0x7fba0e98e8f0 base::Thread::Stop()
#6 0x00000034bb2d dbus::TestService::~TestService()
#7 0x0000003424eb dbus::SignalSenderVerificationTest_TestOwnerStealing_Test::TestBody()
#8 0x0000003ecf9e testing::internal::HandleSehExceptionsInMethodIfSupported<>()
#9 0x0000003dfd62 testing::internal::HandleExceptionsInMethodIfSupported<>()
#10 0x0000003ca3d6 testing::Test::Run()
#11 0x0000003caf2d testing::TestInfo::Run()
#12 0x0000003cb98c testing::TestCase::Run()
#13 0x0000003d76ac testing::internal::UnitTestImpl::RunAllTests()
#14 0x0000003ed0ae testing::internal::HandleSehExceptionsInMethodIfSupported<>()
#15 0x0000003e1432 testing::internal::HandleExceptionsInMethodIfSupported<>()
#16 0x0000003d72ee testing::UnitTest::Run()
#17 0x000000428a71 RUN_ALL_TESTS()
#18 0x000000426672 base::TestSuite::Run()
#19 0x000000316e4d _ZN4base8internal13FunctorTraitsIMN4dbus17ObjectManagerTestEFvvEvE6InvokeIPNS2_57ObjectManagerTest_PropertiesChangedAsObjectsReceived_TestEJEEEvS5_OT_DpOT0_
#20 0x000000316dc4 _ZN4base8internal12InvokeHelperILb0EvE8MakeItSoIRKMN4dbus17ObjectManagerTestEFvvEJPNS4_57ObjectManagerTest_PropertiesChangedAsObjectsReceived_TestEEEEvOT_DpOT0_
#21 0x000000316d75 _ZN4base8internal7InvokerINS0_9BindStateIMN4dbus17ObjectManagerTestEFvvEJNS0_17UnretainedWrapperINS3_57ObjectManagerTest_PropertiesChangedAsObjectsReceived_TestEEEEEEFvvEE7RunImplIRKS6_RKNSt3__15tupleIJS9_EEEJLm0EEEEvOT_OT0_NSG_16integer_sequenceImJXspT1_EEEE
#22 0x000000316d0c _ZN4base8internal7InvokerINS0_9BindStateIMN4dbus17ObjectManagerTestEFvvEJNS0_17UnretainedWrapperINS3_57ObjectManagerTest_PropertiesChangedAsObjectsReceived_TestEEEEEEFvvEE3RunEPNS0_13BindStateBaseE
#23 0x00000043119d _ZNKR4base17RepeatingCallbackIFvvEE3RunEv
#24 0x0000004319f7 base::(anonymous namespace)::LaunchUnitTestsInternal()
#25 0x000000431865 base::LaunchUnitTests()
#26 0x0000004263cd main
#27 0x7fba0d930f45 __libc_start_main
#28 0x000000293029 <unknown>