http/tests/xmlhttprequest/workers/abort-exception-assert.html times out on many bots: http://webkit-test-results.appspot.com/dashboards/flakiness_dashboard.html#showAllRuns=true&showExpectations=true&revision=177232&tests=http%2Ftests%2Fxmlhttprequest%2Fworkers%2Fabort-exception-assert.html
Added to TestExpectations in r177237. This may be due to garbage collection unpredictability, I'm not sure if this way of testing is even valid.