fixing missing import in plot_canvas_toolbar.py
fixing missing import in plot_canvas_toolbar.py

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