According to specification (http://xhr.spec.whatwg.org/#interface-formdata), FormData.append() takes at least 2 arguments. The JSC custom implementation of FormData.append() currently does nothing if less than 2 arguments are provided. I believe we should throw a SyntaxError in this case. Note that the V8 custom implementation is already throwing a SyntaxError in this case so this would make them behave consistently. Also note that Firefox and Opera are throwing an exception for this case as well.
sorry, I fogot to land a patch... see the discussion in bug 84650 *** This bug has been marked as a duplicate of bug 84650 ***