public void onStart() {
            // stub
        }
Get the shuffle edge for item at position when top of
item is at y-coord top. Assumes that current item heights
are consistent with current float view location and
thus expanded positions and slide fraction. i.e. Should not be
called between update of expanded positions/slide fraction
and layoutChildren.

@param position 
@param top
@param height Height of item at position. If -1, this function
calculates this height.

@return Shuffle line between position-1 and position (for
the given view of the list; that is, for when top of item at
position has y-coord of given `top`). If
floating View (treated as horizontal line) is dropped
immediately above this line, it lands in position-1. If
dropped immediately below this line, it lands in position.
third_party/DragSortListView/src/com/mobeta/android/dslv/DragSortListView.java