Update layout test filter for network service.

Mark the following test with Timeout:
http/tests/appcache/local-content.html

BUG=729849
TBR=mmenke@chromium.org

Change-Id: I52c4c9c91c6dc0d68c520fbe5e47ed3e7f8e9345
Reviewed-on: https://chromium-review.googlesource.com/673803Reviewed-by: Yuzhu Shen <yzshen@chromium.org>
Commit-Queue: Yuzhu Shen <yzshen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502962}

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

@@ -126,6 +126,7 @@ Bug(none) fast/xsl/xslt-multiple-relative-import.xml [ Skip ]
 Bug(none) fast/xsl/xslt-nested-stylesheets.xml [ Skip ]
 Bug(none) fast/xsl/xslt-second-level-import.xml [ Skip ]
 Bug(none) fullscreen/compositor-touch-hit-rects-fullscreen-video-controls.html [ Failure ]
+Bug(none) http/tests/appcache/local-content.html [ Timeout ]
 Bug(none) http/tests/background_fetch/background-fetch-click-event.https.html [ Crash Timeout ]
 Bug(none) http/tests/background_fetch/background-fetch-event.https.html [ Crash Timeout ]
 Bug(none) http/tests/background_fetch/background-fetch-fail-event.https.html [ Crash Timeout ]