Somewhere in the range of CLs  377573 : 378572
(see all changes in this range here:
https://chromium.googlesource.com/chromium/src/+log/4a2b9f4adb2209dfdea7d09be0c78b9a9b3dda34%5E..55f2d0ef786093c3ea01cfd019903ab20e68661a?pretty=fuller)

the following tests started to leak on 2 bots:
WebKit Linux Leak
WebKit Linux non-Oilpan Leak

The initial occurrence was masked by a crasher that went in before (was later reverted), so it is hard to narrow down the CL range.

Here is a list of failed tests:
Regressions: Unexpected leaks (24)
  fast/workers/worker-document-leak.html [ Leak Failure Leak Leak ]
  http/tests/local/serviceworker/fetch-request-body-file.html [ Leak ]
  http/tests/serviceworker/chromium/clients-openwindow.html [ Leak ]
  http/tests/serviceworker/chromium/usecounter-on-claim.html [ Leak ]
  http/tests/serviceworker/chromium/usecounter-on-reload.html [ Leak ]
  http/tests/serviceworker/claim-not-using-registration.html [ Leak ]
  http/tests/serviceworker/claim-using-registration.html [ Leak ]
  http/tests/serviceworker/client-id.html [ Leak ]
  http/tests/serviceworker/clients-get-client-types.html [ Leak ]
  http/tests/serviceworker/clients-matchall-client-types.html [ Leak ]
  http/tests/serviceworker/controller-on-reload.html [ Leak ]
  http/tests/serviceworker/fetch-event-async-respond-with.html [ Leak ]
  http/tests/serviceworker/fetch-event-network-error.html [ Leak ]
  http/tests/serviceworker/fetch-event-respond-with-argument.html [ Leak ]
  http/tests/serviceworker/fetch-event-respond-with-stops-propagation.html [ Leak ]
  http/tests/serviceworker/multiple-register.html [ Leak ]
  http/tests/serviceworker/ready.html [ Leak ]
  http/tests/serviceworker/register-same-scope-different-script-url.html [ Leak ]
  http/tests/serviceworker/registration-iframe.html [ Leak ]
  http/tests/serviceworker/shared-worker-controlled.html [ Leak ]
  http/tests/serviceworker/skip-waiting-installed.html [ Leak ]
  http/tests/serviceworker/skip-waiting-using-registration.html [ Leak ]
  http/tests/serviceworker/unregister-then-register-new-script.html [ Leak ]
  virtual/sharedarraybuffer/fast/workers/worker-document-leak.html [ Leak ]

This is typical error message:
11:31:34.053 23087 worker/1 http/tests/serviceworker/unregister-then-register-new-script.html leaked
11:31:34.055 23025 [17754/39510] http/tests/serviceworker/unregister-then-register-new-script.html failed unexpectedly (leak detected: ({"numberOfLiveActiveDOMObjects":[2,3],"numberOfLiveDocuments":[1,2],"numberOfLiveNodes":[4,25],"numberOfLiveResources":[0,1]}))
11:31:34.054 23087 worker/1 http/tests/serviceworker/unregister-then-register-new-script.html failed:
11:31:34.054 23087 worker/1  leak detected: ({"numberOfLiveActiveDOMObjects":[2,3],"numberOfLiveDocuments":[1,2],"numberOfLiveNodes":[4,25],"numberOfLiveResources":[0,1]})