REGRESSION: Layout Test http/tests/security/cross-origin-css-resource-timing.html is flaky

[Truitt Savell]

The following layout test is flaky on MacOS and iOS

http/tests/security/cross-origin-css-resource-timing.html

Probable cause:

Unknown regression point. the failure began 12/2 and is failing almost everywhere. I am unable to reproduce the issue locally with any command. 

Flakiness Dashboard:

https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=http%2Ftests%2Fsecurity%2Fcross-origin-css-resource-timing.html

Diff:
--- /Volumes/Data/slave/highsierra-release-tests-wk1/build/layout-test-results/http/tests/security/cross-origin-css-resource-timing-expected.txt
+++ /Volumes/Data/slave/highsierra-release-tests-wk1/build/layout-test-results/http/tests/security/cross-origin-css-resource-timing-actual.txt
@@ -1,3 +1,5 @@
+CONSOLE MESSAGE: Unhandled Promise Rejection: Error: assert_false: import expected false got true
+Test
 
-PASS CSS subresources of an opaque stylesheet should not populate resource timing entries 
+FAIL CSS subresources of an opaque stylesheet should not populate resource timing entries assert_false: import expected false got true

[Truitt Savell]

the regression point seems to be in the range of r238766-238782 while layout tests were broken.

[Truitt Savell]

looks like https://trac.webkit.org/changeset/238770/webkit may have something to do with it as it directly effected css resource timing.

[Radar WebKit Bug Importer]

<rdar://problem/46492201>

[youenn fablet]

Created attachment 356654 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 356654 [details]
Patch

Clearing flags on attachment: 356654

Committed r238917: <https://trac.webkit.org/changeset/238917>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.