Disable flaky test worker-interception.https.html

Bug: 998399
Change-Id: Ifccc12c536540c3f7cfe257a6f778034a5b07053
TBR: nhiroki@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1789686Reviewed-by: Ian Clelland <iclelland@chromium.org>
Commit-Queue: Ian Clelland <iclelland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694268}

third_party/blink/web_tests/TestExpectations

@@ -6337,3 +6337,6 @@ crbug.com/1000768 [ Linux ] external/wpt/storage/idlharness.https.any.html [ Pas
 
 # Partial fix to avoid a regression on eval(string) with Trusted Types enabled in Chrome 77.
 crbug.com/992424 external/wpt/trusted-types/block-eval.tentative.html [ Failure ]
+
+# Sheriff 2019-09-06
+crbug.com/998399 [ Linux ] virtual/omt-worker-fetch/external/wpt/service-workers/service-worker/worker-interception.https.html [ Pass Timeout ]