Adam Barth 5a5fcb959d Scrollable sometimes pushes frames forever
We were setting a negative velocity tolerance, which never triggered because we
assume tolerances are positive numbers. Now we use a positive tolerance and
assert to catch this case in the future.

Fixes #2765
2016-03-21 12:21:24 -07:00
..
2016-03-12 18:33:47 -08:00