Steps to Reproduce

1. Initialize a dropdown with onChange handler
2. Do some action(ie. click) to trigger the dropdown selection
3. onChnage handler is called but $choice argument is empty

Expected
$choice argument contains jQuery element

Result
$choice is undefined

Testcase
http://jsfiddle.net/y7npxb3d/

One more thing to comment
Dropdown's action setting has the function signagure text, value, element while onChange has value, text, $choice. What about making those two have the same form?