[ RUN      ] ResourceLoadingHintsBrowserTest.ExperimentalHints_ExperimentIsNotEnabled
[2766:2766:1112/161552.250642:WARNING:password_store_factory.cc(261)] Using basic (unencrypted) store for password storage. See https://chromium.googlesource.com/chromium/src/+/master/docs/linux_password_storage.md for more information about password storage options.
[2766:2802:1112/161552.289187:ERROR:bus.cc(396)] Failed to connect to the bus: Could not parse server address: Unknown address type (examples of valid types are "tcp" and on UNIX "unix")

(browser_tests:2766): LIBDBUSMENU-GLIB-WARNING **: Unable to get session bus: Unknown or unsupported transport 'disabled' for address 'disabled:'
[2766:2845:1112/161552.496687:WARNING:embedded_test_server.cc(239)] Request not handled. Returning 404: /non_existent_file.js
[2766:2845:1112/161552.512008:WARNING:embedded_test_server.cc(239)] Request not handled. Returning 404: /foo.jpg
[2766:2845:1112/161552.513073:WARNING:embedded_test_server.cc(239)] Request not handled. Returning 404: /bar.jpg
[2766:2845:1112/161552.515162:WARNING:embedded_test_server.cc(239)] Request not handled. Returning 404: /favicon.ico
../../base/test/metrics/histogram_tester.cc:202: Failure
Expected equality of these values:
  expected_count
    Which is: 1
  actual_count
    Which is: 0
Histogram "Previews.EligibilityReason.ResourceLoadingHints" does not have the right number of samples (1) in the expected bucket (0). It has (0).
Stack trace:
#0 0x5638f4cde13c testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop()
#1 0x5638f4cddb09 testing::internal::AssertHelper::operator=()
#2 0x5638f6c48138 base::HistogramTester::CheckBucketCount()
#3 0x5638f6c48609 base::HistogramTester::ExpectBucketCount()
#4 0x5638f3d274ea ResourceLoadingHintsBrowserTest_ExperimentalHints_ExperimentIsNotEnabled_Test::RunTestOnMainThread()
#5 0x5638f70c8028 content::BrowserTestBase::ProxyRunTestOnMainThreadLoop()
#6 0x5638f6c8d9da ChromeBrowserMainParts::PreMainMessageLoopRunImpl()
#7 0x5638f6c8c64c ChromeBrowserMainParts::PreMainMessageLoopRun()
#8 0x5638f570d3ca content::BrowserMainLoop::PreMainMessageLoopRun()
#9 0x5638f5ab0447 content::StartupTaskRunner::RunAllTasksNow()
#10 0x5638f570bdf6 content::BrowserMainLoop::CreateStartupTasks()
#11 0x5638f570fbd0 content::BrowserMainRunnerImpl::Initialize()
#12 0x5638f5709d04 content::BrowserMain()
#13 0x5638f69142ac content::ContentMainRunnerImpl::Run()
#14 0x5638f868a0cc service_manager::Main()
#15 0x5638f69124e1 content::ContentMain()
#16 0x5638f70c7c1e content::BrowserTestBase::SetUp()
#17 0x5638f6c390a5 InProcessBrowserTest::SetUp()
#18 0x5638f3d29ecb ResourceLoadingHintsBrowserTest::SetUp()

2766:2766:1112/161553.263105:WARNING:pref_notifier_impl.cc(23)] Pref observer found at shutdown.
[2766:2766:1112/161553.264611:WARNING:pref_notifier_impl.cc(23)] Pref observer found at shutdown.
[  FAILED  ] ResourceLoadingHintsBrowserTest.ExperimentalHints_ExperimentIsNotEnabled, where TypeParam =  and GetParam() =  (1217 ms)
[1/1] ResourceLoadingHintsBrowserTest.ExperimentalHints_ExperimentIsNotEnabled (1571 ms)
1 test failed:
    ResourceLoadingHintsBrowserTest.ExperimentalHints_ExperimentIsNotEnabled (../../chrome/browser/previews/resource_loading_hints/resource_loading_hints_browsertest.cc:399)
[ RUN      ] ResourceLoadingHintsBrowserTest.ExperimentalHints_ExperimentIsNotEnabled
[2851:2851:1112/161553.910660:WARNING:password_store_factory.cc(261)] Using basic (unencrypted) store for password storage. See https://chromium.googlesource.com/chromium/src/+/master/docs/linux_password_storage.md for more information about password storage options.

(browser_tests:2851): LIBDBUSMENU-GLIB-WARNING **: Unable to get session bus: Unknown or unsupported transport 'disabled' for address 'disabled:'
[2851:2887:1112/161554.360727:ERROR:bus.cc(396)] Failed to connect to the bus: Could not parse server address: Unknown address type (examples of valid types are "tcp" and on UNIX "unix")
[2851:2933:1112/161554.880332:WARNING:embedded_test_server.cc(239)] Request not handled. Returning 404: /non_existent_file.js
[2851:2933:1112/161554.893798:WARNING:embedded_test_server.cc(239)] Request not handled. Returning 404: /foo.jpg
[2851:2933:1112/161554.893954:WARNING:embedded_test_server.cc(239)] Request not handled. Returning 404: /bar.jpg
[2851:2933:1112/161554.897445:WARNING:embedded_test_server.cc(239)] Request not handled. Returning 404: /favicon.ico
../../base/test/metrics/histogram_tester.cc:202: Failure
Expected equality of these values:
  expected_count
    Which is: 1
  actual_count
    Which is: 0
Histogram "Previews.EligibilityReason.ResourceLoadingHints" does not have the right number of samples (1) in the expected bucket (0). It has (0).
Stack trace:
#0 0x55662bf5913c testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop()
#1 0x55662bf58b09 testing::internal::AssertHelper::operator=()
#2 0x55662dec3138 base::HistogramTester::CheckBucketCount()
#3 0x55662dec3609 base::HistogramTester::ExpectBucketCount()
#4 0x55662afa24ea ResourceLoadingHintsBrowserTest_ExperimentalHints_ExperimentIsNotEnabled_Test::RunTestOnMainThread()
#5 0x55662e343028 content::BrowserTestBase::ProxyRunTestOnMainThreadLoop()
#6 0x55662df089da ChromeBrowserMainParts::PreMainMessageLoopRunImpl()
#7 0x55662df0764c ChromeBrowserMainParts::PreMainMessageLoopRun()
#8 0x55662c9883ca content::BrowserMainLoop::PreMainMessageLoopRun()
#9 0x55662cd2b447 content::StartupTaskRunner::RunAllTasksNow()
#10 0x55662c986df6 content::BrowserMainLoop::CreateStartupTasks()
#11 0x55662c98abd0 content::BrowserMainRunnerImpl::Initialize()
#12 0x55662c984d04 content::BrowserMain()
#13 0x55662db8f2ac content::ContentMainRunnerImpl::Run()
#14 0x55662f9050cc service_manager::Main()
#15 0x55662db8d4e1 content::ContentMain()
#16 0x55662e342c1e content::BrowserTestBase::SetUp()
#17 0x55662deb40a5 InProcessBrowserTest::SetUp()
#18 0x55662afa4ecb ResourceLoadingHintsBrowserTest::SetUp()

[2851:2851:1112/161555.173188:WARNING:pref_notifier_impl.cc(23)] Pref observer found at shutdown.
[2851:2851:1112/161555.175549:WARNING:pref_notifier_impl.cc(23)] Pref observer found at shutdown.
[  FAILED  ] ResourceLoadingHintsBrowserTest.ExperimentalHints_ExperimentIsNotEnabled, where TypeParam =  and GetParam() =  (1487 ms)
[1/1] ResourceLoadingHintsBrowserTest.ExperimentalHints_ExperimentIsNotEnabled (1834 ms)
1 test failed:
    ResourceLoadingHintsBrowserTest.ExperimentalHints_ExperimentIsNotEnabled (../../chrome/browser/previews/resource_loading_hints/resource_loading_hints_browsertest.cc:399)

Build	chromium.linux/linux-xenial-rel/4852
Step	browser_tests on Ubuntu-16.04

Any updates here?

This seems to have fixed, and is much less flaky now (from https://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=ResourceLoadingHintsBrowserTest).