Bug 848803: LICM shouldn't hoist intructions that depend on instruction in or after the loop, r=jandem
Bug 849246 - Follow the scroll velocity for the dynamic toolbar. r=kats

In the rare situation that you cause a fast fling with a very short motion,
it's possible that the toolbar won't hide/show as you expect. Fix this by
saying that any swipe that's faster than the default animation speed
dictates the direction in which the toolbar moves.