tiled-drawing/scrolling/scroll-snap/scroll-snap-mandatory-2d-overflow.html is flaky, potentially for multiple reasons: - when we check that scroll snap animation is done, we don't check that both horizontal and vertical ones are done; - the test sends events in a manner that doesn't match what we'd get from the system.
Marked as flaky in r188896.
<rdar://problem/59527855>
Reset expectations here: https://trac.webkit.org/changeset/256782/webkit
<rdar://problem/59527877>