UkmBrowserTest.IncognitoCheck has become flaky on Mac; https://build.chromium.org/p/chromium.mac/builders/Mac10.9%20Tests%20%28dbg%29/builds/42027 is the first occurrence I've found. Mind taking a look, holte@?

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BrowserTestBase received signal: Terminated: 15. Backtrace:
0   libbase.dylib                       0x0000000124dd0d6e base::debug::StackTrace::StackTrace(unsigned long) + 174
1   libbase.dylib                       0x0000000124dd0e0d base::debug::StackTrace::StackTrace(unsigned long) + 29
2   libbase.dylib                       0x0000000124dcf29c base::debug::StackTrace::StackTrace() + 28
3   browser_tests                       0x000000010eaace29 content::(anonymous namespace)::DumpStackTraceSignalHandler(int) + 537
4   libsystem_platform.dylib            0x00007fff92c165aa _sigtramp + 26
5   ???                                 0x00007fff56de40b0 0x0 + 140734650794160
6   libbase.dylib                       0x000000012509c493 base::PlatformThread::Join(base::PlatformThreadHandle) + 83
7   libbase.dylib                       0x00000001250c5f31 base::Thread::Stop() + 305
8   browser_tests                       0x0000000111f6d4cc browser_sync::ProfileSyncService::Shutdown() + 764
9   libkeyed_service_core.dylib         0x000000013db4a795 KeyedServiceFactory::ContextShutdown(base::SupportsUserData*) + 821
10  libkeyed_service_content.dylib      0x000000013f4eade8 BrowserContextKeyedServiceFactory::BrowserContextShutdown(content::BrowserContext*) + 40
11  libkeyed_service_content.dylib      0x000000013f4eb002 BrowserContextKeyedServiceFactory::ContextShutdown(base::SupportsUserData*) + 50
12  libkeyed_service_core.dylib         0x000000013db43482 DependencyManager::DestroyContextServices(base::SupportsUserData*) + 898
13  libkeyed_service_content.dylib      0x000000013f4e6eb8 BrowserContextDependencyManager::DestroyBrowserContextServices(content::BrowserContext*) + 40
14  browser_tests                       0x000000010d587c98 ProfileImpl::~ProfileImpl() + 376
15  browser_tests                       0x000000010d5886b5 ProfileImpl::~ProfileImpl() + 21
16  browser_tests                       0x000000010d5886d9 ProfileImpl::~ProfileImpl() + 25
17  browser_tests                       0x000000010d57678f ProfileDestroyer::DestroyProfileWhenAppropriate(Profile*) + 1231
18  browser_tests                       0x000000010d614124 ProfileManager::ProfileInfo::~ProfileInfo() + 100
19  browser_tests                       0x000000010d614215 ProfileManager::ProfileInfo::~ProfileInfo() + 21
20  browser_tests                       0x000000010d61ec9e linked_ptr<ProfileManager::ProfileInfo>::depart() + 78
21  browser_tests                       0x000000010d61ec45 linked_ptr<ProfileManager::ProfileInfo>::~linked_ptr() + 21
22  browser_tests                       0x000000010d613e65 linked_ptr<ProfileManager::ProfileInfo>::~linked_ptr() + 21
23  browser_tests                       0x000000010d615e03 std::__1::pair<base::FilePath const, linked_ptr<ProfileManager::ProfileInfo> >::~pair() + 35
24  browser_tests                       0x000000010d615dd5 std::__1::pair<base::FilePath const, linked_ptr<ProfileManager::ProfileInfo> >::~pair() + 21
25  browser_tests                       0x000000010d615d45 std::__1::__tree<std::__1::__value_type<base::FilePath, linked_ptr<ProfileManager::ProfileInfo> >, std::__1::__map_value_compare<base::FilePath, std::__1::__value_type<base::FilePath, linked_ptr<ProfileManager::ProfileInfo> >, std::__1::less<base::FilePath>, true>, std::__1::allocator<std::__1::__value_type<base::FilePath, linked_ptr<ProfileManager::ProfileInfo> > > >::destroy(std::__1::__tree_node<std::__1::__value_type<base::FilePath, linked_ptr<ProfileManager::ProfileInfo> >, void*>*) + 213
26  browser_tests                       0x000000010d615c67 std::__1::__tree<std::__1::__value_type<base::FilePath, linked_ptr<ProfileManager::ProfileInfo> >, std::__1::__map_value_compare<base::FilePath, std::__1::__value_type<base::FilePath, linked_ptr<ProfileManager::ProfileInfo> >, std::__1::less<base::FilePath>, true>, std::__1::allocator<std::__1::__value_type<base::FilePath, linked_ptr<ProfileManager::ProfileInfo> > > >::~__tree() + 87
27  browser_tests                       0x000000010d615c05 std::__1::__tree<std::__1::__value_type<base::FilePath, linked_ptr<ProfileManager::ProfileInfo> >, std::__1::__map_value_compare<base::FilePath, std::__1::__value_type<base::FilePath, linked_ptr<ProfileManager::ProfileInfo> >, std::__1::less<base::FilePath>, true>, std::__1::allocator<std::__1::__value_type<base::FilePath, linked_ptr<ProfileManager::ProfileInfo> > > >::~__tree() + 21
28  browser_tests                       0x000000010d615be5 std::__1::map<base::FilePath, linked_ptr<ProfileManager::ProfileInfo>, std::__1::less<base::FilePath>, std::__1::allocator<std::__1::pair<base::FilePath const, linked_ptr<ProfileManager::ProfileInfo> > > >::~map() + 21
29  browser_tests                       0x000000010d6004e5 std::__1::map<base::FilePath, linked_ptr<ProfileManager::ProfileInfo>, std::__1::less<base::FilePath>, std::__1::allocator<std::__1::pair<base::FilePath const, linked_ptr<ProfileManager::ProfileInfo> > > >::~map() + 21
30  browser_tests                       0x000000010d600315 ProfileManager::~ProfileManager() + 581
31  browser_tests                       0x000000010d600525 ProfileManager::~ProfileManager() + 21
32  browser_tests                       0x000000010d600569 ProfileManager::~ProfileManager() + 25
33  browser_tests                       0x000000010cdedc20 BrowserProcessImpl::StartTearDown() + 2896
34  browser_tests                       0x000000010cf05044 ChromeBrowserMainParts::PostMainMessageLoopRun() + 1060
35  libcontent.dylib                    0x000000012f4810a0 content::BrowserMainLoop::ShutdownThreadsAndCleanUp() + 896
36  libcontent.dylib                    0x000000012f48b645 content::BrowserMainRunnerImpl::Shutdown() + 2389
37  libcontent.dylib                    0x000000012f4748b6 content::BrowserMain(content::MainFunctionParams const&) + 454
38  libcontent.dylib                    0x00000001319c18b5 content::RunNamedProcessTypeMain(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, content::MainFunctionParams const&, content::ContentMainDelegate*) + 581
39  libcontent.dylib                    0x00000001319c3382 content::ContentMainRunnerImpl::Run() + 1938
40  libcontent.dylib                    0x00000001319bfecd content::ContentServiceManagerMainDelegate::RunEmbedderProcess() + 61
41  libembedder.dylib                   0x0000000150781114 service_manager::Main(service_manager::MainParams const&) + 1892
42  libcontent.dylib                    0x00000001319c1629 content::ContentMain(content::ContentMainParams const&) + 89
43  browser_tests                       0x000000010eaac377 content::BrowserTestBase::SetUp() + 4919
44  browser_tests                       0x000000010ccd126e InProcessBrowserTest::SetUp() + 2126
45  browser_tests                       0x000000010ccb191b SyncTest::SetUp() + 3963
46  browser_tests                       0x000000010aeb20ae void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) + 126
47  browser_tests                       0x000000010ae8dba2 void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) + 114
48  browser_tests                       0x000000010ae8da84 testing::Test::Run() + 116
49  browser_tests                       0x000000010ae8ebbd testing::TestInfo::Run() + 221
50  browser_tests                       0x000000010ae8ff1c testing::TestCase::Run() + 236
51  browser_tests                       0x000000010ae9d30a testing::internal::UnitTestImpl::RunAllTests() + 922
52  browser_tests                       0x000000010aeb542e bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) + 126
53  browser_tests                       0x000000010ae9cef2 bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) + 114
54  browser_tests                       0x000000010ae9cdce testing::UnitTest::Run() + 366
55  browser_tests                       0x000000010cd240d1 RUN_ALL_TESTS() + 17
56  browser_tests                       0x000000010cd2347e base::TestSuite::Run() + 334
57  browser_tests                       0x000000010cc69e23 ChromeTestSuiteRunner::RunTestSuite(int, char**) + 67
58  browser_tests                       0x000000010cc69f99 ChromeTestLauncherDelegate::RunTestSuite(int, char**) + 57
59  browser_tests                       0x000000010eba078d content::LaunchTests(content::TestLauncherDelegate*, int, int, char**) + 733
60  browser_tests                       0x000000010cc6ae8e LaunchChromeTests(int, content::TestLauncherDelegate*, int, char**) + 46
61  browser_tests                       0x000000010cc69cef main + 239
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