Request from Dean.

Currently there is a lag (for two reasons) when you drag the scrollbar bubble. 

1)  The scrollbar waits 25 pixels to determine if you really meant drag. Since you are in the lozenge you always really mean drag, except when you are in the buffer zone (at the ends, where any press is treated as a page). So when touching the lozenge or in the buffer zone, drag instantly. 

Possibly, the buffer zone could be ignored if the bubble is already at the ends, but this might lead to the following problem: rapid touching to get to an end: touch touch touch (hit end) touch (oops drag started) screen moves slightly.

2)  In the current design, the scrollbar isn't sticky to the finger origin point. Instead the scrollbar only move when you reach the end of the bubble. Instead the scollbar should drag from the origin point (or the drag kickoff point if drag checking is in play)