From Findit:
https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVygAILEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCLJAWNocm9taXVtLm1hYy9NYWMxMC45IFRlc3RzIChkYmcpLzQ2MDc5L2Jyb3dzZXJfdGVzdHMvVTJWeWRtbGpaVmR2Y210bGNreGhlbmxDWVdOclozSnZkVzVrVkdWemRGZHBkR2hPWVhScGRtVkNhVzVrYVc1bmN5OVRaWEoyYVdObFYyOXlhMlZ5VEdGNmVVSmhZMnRuY205MWJtUlVaWE4wTGtacGJIUmxjbVZrUlhabGJuUnpRV1owWlhKU1pYTjBZWEowTHpBPQwLEhNNYXN0ZXJGbGFrZUFuYWx5c2lzGAEM

Master	Builder	Step	Test
1	chromium.mac	Mac10.9 Tests (dbg)	browser_tests	ServiceWorkerLazyBackgroundTestWithNativeBindings/ServiceWorkerLazyBackgroundTest.FilteredEventsAfterRestart/0
Culprit: https://crrev.com/507762

Since this test exercises a browser restart to test persistence of filtered events, it's likely there is something going wrong.

When I look at the findit page, I see it points to:
https://luci-milo.appspot.com/buildbot/chromium.mac/Mac10.9%20Tests%20(dbg)/45964
But I can't find any test failures in that build. Anyway, will keep an eye on it.