redraw a ColorBar when any of its mappers' traits change
redraw a ColorBar when any of its mappers' traits change

tommy-u/chaco,burnpanck/chaco,tommy-u/chaco,ContinuumIO/chaco,burnpanck/chaco,ContinuumIO/chaco,burnpanck/chaco,tommy-u/chaco,ContinuumIO/chaco,ContinuumIO/chaco