LayoutTest inspector/canvas/context-attributes.html is a flaky timeout https://build.webkit.org/builders/Apple%20El%20Capitan%20Debug%20WK1%20(Tests)/builds/2124 https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=inspector%2Fcanvas%2Fcontext-attributes.html
This test was added with http://trac.webkit.org/changeset/218618 and appears to have been flaky since the start.
Marked test as flaky in https://trac.webkit.org/changeset/220884/webkit