Failed in 
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/linux-chromeos-rel/18726
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/linux-chromeos-rel/18730

Not sure why it is more flaky under single process mash.

Sample log:
[ RUN      ] ResourceLoadingHintsBrowserTest.ResourceLoadingHintsHttpsWhitelisted
[1:1:0117/000438.393878:INFO:hugepage_text.cc(68)] Mlocking text pages failed: Cannot allocate memory (12)
[9861:9861:0117/000438.431537:WARNING:chrome_browser_main_chromeos.cc(547)] Running as stub user with profile dir: test-user
[9861:9861:0117/000438.585778:INFO:remote_commands_service.cc(38)] Fetching remote commands.
[9861:9861:0117/000438.601129:WARNING:remote_commands_service.cc(40)] Client is not registered.
[9861:9861:0117/000438.601264:INFO:remote_commands_invalidator.cc(32)] Initialize RemoteCommandsInvalidator.
[9861:9861:0117/000438.601300:INFO:remote_commands_invalidator.cc(57)] Starting RemoteCommandsInvalidator.
[9861:9861:0117/000438.601329:INFO:remote_commands_invalidator.cc(123)] RemoteCommandsInvalidator ReloadPolicyData.
[9861:9861:0117/000438.601357:INFO:remote_commands_invalidator.cc(167)] Unregister RemoteCommandsInvalidator.
[9861:9861:0117/000438.629098:WARNING:wallpaper_controller_client.cc(358)] Cannot get wallpaper files id in RemovePolicyWallpaper. This should never happen under normal circumstances.
[9861:9861:0117/000438.761448:ERROR:gpu_interface_provider.cc(87)] Not implemented reached in virtual void content::GpuInterfaceProvider::RegisterOzoneGpuInterfaces(service_manager::BinderRegistry *)
[9861:9861:0117/000438.806084:ERROR:remote_text_input_client.cc(144)] Not implemented reached in virtual void RemoteTextInputClient::OnInputMethodChanged()
[9861:9861:0117/000438.806315:ERROR:remote_text_input_client.cc(101)] Not implemented reached in virtual ui::TextInputClient::FocusReason RemoteTextInputClient::GetFocusReason() const
[9861:9861:0117/000438.806324:ERROR:remote_text_input_client.cc(185)] Not implemented reached in virtual bool RemoteTextInputClient::ShouldDoLearning()
[9861:9861:0117/000438.806366:ERROR:remote_text_input_client.cc(95)] Not implemented reached in virtual bool RemoteTextInputClient::HasCompositionText() const
[9861:9861:0117/000438.806373:ERROR:remote_text_input_client.cc(107)] Not implemented reached in virtual bool RemoteTextInputClient::GetTextRange(gfx::Range *) const
[9861:9861:0117/000438.877294:ERROR:render_widget_host_view_aura.cc(1308)] Not implemented reached in virtual base::i18n::TextDirection content::RenderWidgetHostViewAura::GetTextDirection() const
[9861:10189:0117/000438.900438:WARNING:embedded_test_server.cc(237)] Request not handled. Returning 404: /non_existent_file.js
[9861:10189:0117/000438.914272:WARNING:embedded_test_server.cc(237)] Request not handled. Returning 404: /foo.jpg
[9861:10189:0117/000438.917260:WARNING:embedded_test_server.cc(237)] Request not handled. Returning 404: /bar.jpg
../../chrome/browser/previews/resource_loading_hints/resource_loading_hints_browsertest.cc:251: Failure
Value of: expect.second
  Actual: false
Expected: true
Stack trace:
#0 0x56156d53a61c testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop()
#1 0x56156d539f69 testing::internal::AssertHelper::operator=()
#2 0x56156c0b2b0d ResourceLoadingNoFeaturesBrowserTest::MonitorResourceRequestOnUIThread()
#3 0x56156f72c105 base::debug::TaskAnnotator::RunTask()
#4 0x56156f69ffbf base::MessageLoopImpl::RunTask()
#5 0x56156f6a0493 base::MessageLoopImpl::DoWork()
#6 0x56156f728719 base::MessagePumpLibevent::Run()
#7 0x56156f6be009 base::RunLoop::Run()
#8 0x56156fc27aa1 content::MessageLoopRunner::Run()
#9 0x56156f77abe5 ui_test_utils::NavigateToURLWithDispositionBlockUntilNavigationsComplete()
#10 0x56156c0ae2d4 ResourceLoadingHintsBrowserTest_ResourceLoadingHintsHttpsWhitelisted_Test::RunTestOnMainThread()
#11 0x56156fc0407f content::BrowserTestBase::ProxyRunTestOnMainThreadLoop()
#12 0x56156f7c582e ChromeBrowserMainParts::PreMainMessageLoopRunImpl()
#13 0x56156f7c4802 ChromeBrowserMainParts::PreMainMessageLoopRun()
#14 0x56156d0ced72 chromeos::ChromeBrowserMainPartsChromeos::PreMainMessageLoopRun()
#15 0x56156df9db82 content::BrowserMainLoop::PreMainMessageLoopRun()
#16 0x56156e32fdb7 content::StartupTaskRunner::RunAllTasksNow()
#17 0x56156df9c97d content::BrowserMainLoop::CreateStartupTasks()
#18 0x56156df9fa52 content::BrowserMainRunnerImpl::Initialize()
#19 0x56156df9ae8f content::BrowserMain()
#20 0x56156f306e5a content::ContentMainRunnerImpl::RunServiceManager()
#21 0x56156f306ad6 content::ContentMainRunnerImpl::Run()
#22 0x5615714627cd service_manager::Main()
#23 0x56156f305024 content::ContentMain()
#24 0x56156fc03b97 content::BrowserTestBase::SetUp()
#25 0x56156f7772bb InProcessBrowserTest::SetUp()
#26 0x56156c0b132b ResourceLoadingHintsBrowserTest::SetUp()

[9861:10189:0117/000439.085978:WARNING:embedded_test_server.cc(237)] Request not handled. Returning 404: /favicon.ico
BrowserTestBase received signal: Terminated. Backtrace:
#0 0x56156f716a8f base::debug::StackTrace::StackTrace()
#1 0x56156fc04a22 content::(anonymous namespace)::DumpStackTraceSignalHandler()
#2 0x7ff915074cb0 <unknown>
#3 0x56156f6a26b3 base::BucketRanges::ResetChecksum()
#4 0x56156f6ad67c base::PersistentHistogramAllocator::CreateHistogram()
#5 0x56156f6ad42f base::PersistentHistogramAllocator::GetHistogram()
#6 0x56156f6ad363 base::PersistentHistogramAllocator::Iterator::GetNextWithIgnore()
#7 0x56156f84a803 SubprocessMetricsProvider::MergeHistogramDeltas()
#8 0x56156c0aeda2 (anonymous namespace)::RetryForHistogramUntilCountReached()
#9 0x56156c0ae329 ResourceLoadingHintsBrowserTest_ResourceLoadingHintsHttpsWhitelisted_Test::RunTestOnMainThread()
#10 0x56156fc0407f content::BrowserTestBase::ProxyRunTestOnMainThreadLoop()
#11 0x56156f7c582e ChromeBrowserMainParts::PreMainMessageLoopRunImpl()
#12 0x56156f7c4802 ChromeBrowserMainParts::PreMainMessageLoopRun()
#13 0x56156d0ced72 chromeos::ChromeBrowserMainPartsChromeos::PreMainMessageLoopRun()
#14 0x56156df9db82 content::BrowserMainLoop::PreMainMessageLoopRun()
#15 0x56156e32fdb7 content::StartupTaskRunner::RunAllTasksNow()
#16 0x56156df9c97d content::BrowserMainLoop::CreateStartupTasks()
#17 0x56156df9fa52 content::BrowserMainRunnerImpl::Initialize()
#18 0x56156df9ae8f content::BrowserMain()
#19 0x56156f306e5a content::ContentMainRunnerImpl::RunServiceManager()
#20 0x56156f306ad6 content::ContentMainRunnerImpl::Run()
#21 0x5615714627cd service_manager::Main()
#22 0x56156f305024 content::ContentMain()
#23 0x56156fc03b97 content::BrowserTestBase::SetUp()
#24 0x56156f7772bb InProcessBrowserTest::SetUp()
#25 0x56156c0b132b ResourceLoadingHintsBrowserTest::SetUp()
#26 0x56156d540130 testing::Test::Run()
#27 0x56156d540ecf testing::TestInfo::Run()
#28 0x56156d5413f7 testing::TestCase::Run()
#29 0x56156d54d3b7 testing::internal::UnitTestImpl::RunAllTests()
#30 0x56156d54cf36 testing::UnitTest::Run()
#31 0x56156f78d0b9 base::TestSuite::Run()
#32 0x56156f67b68d ChromeTestSuiteRunner::RunTestSuite()
#33 0x56156fc23e0c content::LaunchTests()
#34 0x56156f67bb32 LaunchChromeTests()
#35 0x56156f67b61e main
#36 0x7ff91505ff45 __libc_start_main
#37 0x56156bba4aea _start