Custom Control- sap.m.Dialog

Hello Friends,

I need your help on extending new controls in SAPUI5.

Scenario:

As we know sap.m.Dialog control is available in SAPUI5 library. I am trying to add one new aggregation property to this control. (for eg: By default it has to show ComboBox)

JS Link:

http://jsbin.com/kabodi/edit?html,js,output

I am struck in render property. It could be a great helpful if you share your ideas with me

Thanks in advance

KA