Specifically:

2018-12-03 03:41:01.913 browser_tests[15969:187076] *** WARNING: Textured window <NativeWidgetMacNSWindow: 0x7fc20271c110> is getting an implicitly transparent titlebar. This will break when linking against newer SDKs. Use NSWindow's -titlebarAppearsTransparent=YES instead.
../../chrome/browser/ui/cocoa/apps/native_app_window_cocoa_browsertest.mm:198: Failure
Actual function call count doesn't match EXPECT_CALL(*mock_host, OnAppUnhideWithoutActivation())...
         Expected: to be called once
           Actual: never called - unsatisfied and active
Stack trace:
0   browser_tests                       0x000000011029a92b testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop(int) + 91
1   browser_tests                       0x000000011029a2e9 testing::internal::AssertHelper::operator=(testing::Message const&) const + 89
2   browser_tests                       0x00000001102898d1 testing::internal::GoogleTestFailureReporter::ReportFailure(testing::internal::FailureReporterInterface::FailureType, char const*, int, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) + 97
3   browser_tests                       0x000000011028e598 testing::internal::UntypedFunctionMockerBase::VerifyAndClearExpectationsLocked() + 584
4   browser_tests                       0x000000011028ef09 testing::Mock::VerifyAndClearExpectationsLocked(void*) + 393
5   browser_tests                       0x000000011028ed61 testing::Mock::VerifyAndClearExpectations(void*) + 33
6   browser_tests                       0x000000010ff9a0cd NativeAppWindowCocoaBrowserTest_HideShowWithAppWithShim_Test::RunTestOnMainThread() + 3117
7   browser_tests                       0x000000011373b68b content::BrowserTestBase::ProxyRunTestOnMainThreadLoop() + 491
8   browser_tests                       0x000000011317f7b4 ChromeBrowserMainParts::PreMainMessageLoopRunImpl() + 4372
9   browser_tests                       0x000000011317e5dd ChromeBrowserMainParts::PreMainMessageLoopRun() + 45
10  browser_tests                       0x00000001112ea7b2 content::BrowserMainLoop::PreMainMessageLoopRun() + 50
11  browser_tests                       0x000000011174acd7 content::StartupTaskRunner::RunAllTasksNow() + 39
12  browser_tests                       0x00000001112e93eb content::BrowserMainLoop::CreateStartupTasks() + 683
13  browser_tests                       0x00000001112eca55 content::BrowserMainRunnerImpl::Initialize(content::MainFunctionParams const&) + 85
14  browser_tests                       0x00000001112e77d2 content::BrowserMain(content::MainFunctionParams const&) + 178
15  browser_tests                       0x0000000112c07db1 content::ContentMainRunnerImpl::RunServiceManager(content::MainFunctionParams&, bool) + 241
16  browser_tests                       0x0000000112c07c94 content::ContentMainRunnerImpl::Run(bool) + 292
17  browser_tests                       0x0000000115f70fdb service_manager::Main(service_manager::MainParams const&) + 3051
18  browser_tests                       0x0000000112c06e34 content::ContentMain(content::ContentMainParams const&) + 68
19  browser_tests                       0x000000011373b2dd content::BrowserTestBase::SetUp() + 2829
20  browser_tests                       0x00000001130f2d91 InProcessBrowserTest::SetUp() + 529