Rather than changing W3CImportExpectations, I recommend skipping the tests in TestExpectations. Otherwise you'll have to run a new import, and might have a lot of fun with unrelated issues.
qyearsley@, what this suggests to me is that the import script should run any modified tests at least 10 times to avoid importing known flaky tests. It should probably also measure the time taken and disable slow tests.
external/wpt/workers/Worker_cross_origin_security_err.htm should be investigated too. Updating the TestExpectations entry to point at this tracking issue.
Summary: Failing web-platform-tests for workers that pass in Edge, Firefox and Safari (was: 9 failing web-platform-tests for workers that pass in Firefox and Edge)
foolip@: Regarding c#19, sorry for my delayed reply. Yes, recently I started actively working on this to reduce incompatibilities before off-the-main-thread things get more popular.
Comment 1 by shimazu@chromium.org, Oct 6 2016
Status: Assigned (was: Untriaged)