nsIDOMDataContainerEvent Interface

 Return the data associated with the given key.

 @param  key  the key
 @return      the data associated with the key

nsIVariant getData(in DOMString key)

 Set the data for the given key.

 @param  key   the data key
 @param  data  the data
 @throws       NS_ERROR_UNEXPECTED if the method is called during event
               dispatch

void setData(in DOMString key, in nsIVariant data)