mouse: Add property for scroll acceleration curve

This seems to be useful when diagnosing scrolling problems.

TEST=Set the curve to linear (`10,0,0,0,0`) for a mouse, and check that
     the behaviour changes accordingly.

Change-Id: I96f9182f45a855e3e65add62a852730c195f222d
Tested-by: Harry Cutts <>
Auto-Submit: Harry Cutts <>
Reviewed-by: Sean O'Brien <>
Commit-Queue: Harry Cutts <>
2 files changed