It seems like this test is very flaky: http://webkit-test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=css3%2Ffilters%2Fcustom%2Ffilter-fallback-to-software.html I can never get it to work on my machine.
Added test expectation in http://trac.webkit.org/changeset/150195.
Thanks for adding the expectations, Ryosuke. This is a legitimate failure that I need to get around to fixing. *** This bug has been marked as a duplicate of bug 96580 ***