The following layout test is flaky

http/tests/background_fetch/background-fetch-manager-get.https.html

Probable cause:

https://chromium.googlesource.com/chromium/src/+/acdf76e1b5592b15eed80cb566da627599f131a7

See:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_tests&tests=http%2Ftests%2Fbackground_fetch%2Fbackground-fetch-manager-get.https.html

Log:
This is a testharness.js-based test.
PASS BackgroundFetchManager.get() requires an activated Service Worker.
PASS BackgroundFetchManager.get() returns NULL for non-existing fetches.
PASS BackgroundFetchManager.get() can return created fetches.
FAIL BackgroundFetchManager.get() returned fetches can be aborted. assert_equals: expected null but got object "[object BackgroundFetchRegistration]"
Harness: the test ran to completion.