Network service: update layout test filter

Suppress failure of
paint/invalidation/video-paint-invalidation.html

This seems likely to be related to the recent change in the main failure
suppression file:
https://chromium-review.googlesource.com/c/chromium/src/+/690624

BUG=729849
TBR=jam@chromium.org

Change-Id: I656f6f318b4b850c21682bfaf52a299e6346dd4f
Reviewed-on: https://chromium-review.googlesource.com/691066Reviewed-by: Yuzhu Shen <yzshen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505181}

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

@@ -461,6 +461,7 @@ Bug(none) virtual/mojo-loading/http/tests/devtools/sources/debugger-breakpoints/
 Bug(none) virtual/mojo-loading/http/tests/xmlhttprequest/methods-lower-case.html [ Failure Timeout Pass Crash ]
 Bug(none) installedapp/getinstalledrelatedapps-empty.html [ Timeout ]
 Bug(none) installedapp/getinstalledrelatedapps.html [ Timeout ]
+Bug(none) paint/invalidation/video-paint-invalidation.html [ Failure ]
 Bug(none) plugins/iframe-plugin-bgcolor.html [ Timeout ]
 
 Bug(none) virtual [ Crash Failure Timeout ]