@Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        updateScrollStarts();
    }
Set the width of each drag scroll region by specifying
a fraction of the ListView height.

@param upperFrac Fraction of ListView height for up-scroll bound.
Capped at 0.5f.
@param lowerFrac Fraction of ListView height for down-scroll bound.
Capped at 0.5f.
third_party/DragSortListView/src/com/mobeta/android/dslv/DragSortListView.java