This is from https://github.com/web-platform-tests/wpt/pull/13164 which I reviewed. Looking.

For the root clients-matchall-client-types, the test was already failing, and this slightly changed the expectations.

For the virtual/outofblink-cors and outofblink-cors-ns variant,
there are diff expectations for Mac vs other platforms, which we wouldn't expect. The test has been flaky on Mac since at least 612923, which predates this WPT import:
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mac10.10%20Tests/36871
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests&tests=clients-matchall-client-types.https.html

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d96c8eda9afb578f13ed9e952b69c525f539ce7f

commit d96c8eda9afb578f13ed9e952b69c525f539ce7f
Author: Matt Falkenhagen <falken@chromium.org>
Date: Tue Dec 04 09:38:35 2018

Gardening: Tweak outofblink-cors failures after WPT import.

The import bot at https://crrev.com/c/1359866 added Mac expectations for
outofblink-cors/external/wpt/service-workers/service-worker/clients-matchall-client-types,
which is surprising because the test should have no platform
differences. Probably the test is just flaky everywhere. Remove the Mac
expectations in favor of flaky expectations.

Bug:  911442 , 870173
Change-Id: I1cfae61ceee615bcd5654920590a53c0d8447d3e
TBR: toyoshim
Reviewed-on: https://chromium-review.googlesource.com/c/1360453
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613484}
[modify] https://crrev.com/d96c8eda9afb578f13ed9e952b69c525f539ce7f/third_party/blink/web_tests/TestExpectations
[delete] https://crrev.com/4413fc16ca9a076f683f6cdbaa4e43b8166f4c99/third_party/blink/web_tests/platform/mac-mac10.11/virtual/outofblink-cors/external/wpt/service-workers/service-worker/clients-matchall-client-types.https-expected.txt
[delete] https://crrev.com/4413fc16ca9a076f683f6cdbaa4e43b8166f4c99/third_party/blink/web_tests/platform/mac-retina/virtual/outofblink-cors/external/wpt/service-workers/service-worker/clients-matchall-client-types.https-expected.txt

Actually the flakiness on outofblink-cors seems to have disappeared according to flakiness dashboard. I'll remove the flaky expectation.

This change in expectations has been triaged. issue 751959 remains to track this test failing.