Mark virtual/omt-worker-fetch/external/wpt/resource-timing/idlharness.any.worker.html as flaky

TBR=nhiroki@chromium.org

Bug: 990900
Change-Id: I585308ff8ccb07c933f6c79a585a209be194785a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1737093Reviewed-by: Chris Sharp <csharp@chromium.org>
Commit-Queue: Chris Sharp <csharp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#684068}

third_party/blink/web_tests/TestExpectations

@@ -6524,6 +6524,8 @@ crbug.com/989365 [ Win7 ] http/tests/security/img-crossorigin-redirect-credentia
 crbug.com/989014 [ Linux Debug ] external/wpt/cookie-store/serviceworker_cookieStore_subscriptions_eventhandler_attribute.tentative.https.html [ Pass Timeout ]
 crbug.com/989665 [ Win Linux ] virtual/omt-worker-fetch/external/wpt/resource-timing/resource_timing_buffer_full_eventually.html [ Pass Timeout ]
 
+crbug.com/990900 [ Linux ] virtual/omt-worker-fetch/external/wpt/resource-timing/idlharness.any.worker.html [ Pass Timeout ]
+
 # Sheriff 2019-08-01
 crbug.com/989860 [ Mac10.13 Linux Debug ] http/tests/devtools/indexeddb/live-update-indexeddb-list.js [ Pass Failure ]
 crbug.com/989717 [ Fuchsia ] http/tests/preload/avoid_delaying_onload_link_preload.html [ Pass Failure ]