Network service layout tests: Update filter to mark a test as flaky.

external/wpt/service-workers/service-worker/skip-waiting-using-registration.https.html

BUG=729849
TBR=jam@chromium.org

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I3f17e6f0cee0e088a6a3aab58f2b693d80f0296b
Reviewed-on: https://chromium-review.googlesource.com/833230
Reviewed-by: Yuzhu Shen <yzshen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524816}

third_party/WebKit/LayoutTests/FlagExpectations/enable-features=NetworkService

@@ -46,6 +46,7 @@ Bug(none) external/wpt/service-workers/service-worker/navigation-preload/broken-
 Bug(none) external/wpt/service-workers/service-worker/ServiceWorkerGlobalScope/unregister.https.html [ Pass Failure ]
 Bug(none) external/wpt/service-workers/service-worker/appcache-ordering-main.https.html [ Pass Failure ]
 Bug(none) external/wpt/service-workers/service-worker/ready.https.html [ Pass Crash Failure ]
+Bug(none) external/wpt/service-workers/service-worker/skip-waiting-using-registration.https.html [ Pass Timeout ]
 Bug(none) http/tests/local/serviceworker/fetch-request-body-file.html [ Pass Crash Failure ]
 Bug(none) http/tests/serviceworker/chromium/stop-worker-during-respond-with.html [ Pass Failure ]
 Bug(none) http/tests/appcache/top-frame-3.html [ Pass Timeout ]