Change the code in ChartView.java "setValueMarkers" method to not create a new
list listener every time.  The listener is notifying the skin (basically) when
changes in the value markers list happen, so it only needs to be created once
and then assigned to the new list every time the list changes.  And it must
be removed from the old list at that time.  Change the logic to look like all
other such occurrences.

Basically, heap monitoring showed the large number of these listener objects
being created, which are unnecessary.


git-svn-id: https://svn.apache.org/repos/asf/pivot/trunk@1642790 13f79535-47bb-0310-9956-ffa450edef68