Fix selection handles on older API versions

The new assets didn't have the same padding on the edges as assets on older
versions. The adjustments to the getHotspotX code for the new assets broke
how the handles on older API versions were placed.

This CL updates the assets to have the same padding (i.e. handleWidth / 2
on each side of the handle and changes the getHotspotX methods for this.

Bug: 20829391
Change-Id: If7e466d200ef7757831bc763c3c3ce4a8bbf63fc