How to extend a control in a way that the renderer is only extended & not overriden ?

Hi All,

I am trying to extend a Button control. Say, i want the same rendering of the Button control with an additional Border in the extended control. How to do it ? When i tried leaving the renderer method blank in my extended control, its just renders nothing. Now, how to include the renderer of the Button in my extended control.

http://jsbin.com/setuzeti/2/edit

Regards

Sakthivel