nsIXTFBindableElement can be used to add support for new interfaces to
 normal XML elements. XBL bindings do work with this kind of XTF elements.

 @note getScriptingInterfaces don't work at the moment with
 nsIXTFBindableElements. The problem is that XBL does not play nicely
 with that kind of interfaces.
 However, if nsIXTFBindableElement implements scriptable interfaces, those
 can be used by explicitly QIing to them.
[scriptable, uuid(8dcc630c-9adc-4c60-9954-a004cb45e4a7)]
interface nsIXTFBindableElement : nsIXTFElement


 onCreated will be called before any notifications are sent to
 the xtf element.

 @param wrapper is a weak proxy to the wrapping element
 (i.e. holding a reference to this will not create a cycle).
void onCreated(in nsIXTFBindableElementWrapper wrapper)