Fix bug 5173029 - make fast scroller aware of scrolling containers

When a ListView with a FastScroller is located in a scrolling
container, defer the start of the drag operation for a short time or
until a touch slop is crossed. This allows these lists to be placed in
containers like ViewPagers without immediately stealing touch events.

Change-Id: I9b10b6993b24113c5e95c485bf57206747c73a84