[This bug is why fast/forms/submit-nil-value-assert.html started failing following the change]. WebKit doesn't do anything when you submit a form that doesn't have an 'action' attribute. Shipping Safari and Firefox submit the form (using the document's URL; this is also the behavior for action="").
Fixed by Darin in r17662. I still think that test needs a safeguard against hanging DumpRenderTree...