Mark external/wpt/web-locks/idlharness.tentative.https.any.serviceworker.html MSAN timeout

This test is a consistent [ Pass Timeout ] flake on the MSAN bots.

Tbr: rakina@
No-try: true
No-presubmit: true
Bug: 856601
Change-Id: If4d75e81bb8075e3a314e429f24a84dfc7157cc3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1725242
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682124}

third_party/blink/web_tests/MSANExpectations

@@ -312,3 +312,6 @@ crbug.com/856601 [ Linux ] virtual/not-omt-sw-fetch/external/wpt/fetch/api/idl.a
 crbug.com/856601 [ Linux ] virtual/omt-worker-fetch/external/wpt/fetch/cors-rfc1918/idlharness.tentative.any.serviceworker.html [ Pass Timeout ]
 crbug.com/856601 [ Linux ] external/wpt/WebCryptoAPI/idlharness.https.any.html [ Pass Timeout ]
 crbug.com/856601 [ Linux ] external/wpt/web-animations/interfaces/Animation/idlharness.window.html [ Pass Timeout ]
+
+# Sheriff 2019-07-29
+crbug.com/856601 [ Linux ] external/wpt/web-locks/idlharness.tentative.https.any.serviceworker.html [ Pass Timeout ]