#1751 FormData constructor should support form parameter

[Frank Danek]

Currently the FormData JS object only offers a constructor with no arguments.
At least in real FF31 and IE11 the constructor supports a "form" parameter. If given the form's inputs will be added to the FormData.

See https://developer.mozilla.org/en-US/docs/Web/API/FormData/FormData

Please find a patch attached containing a test for this feature.

[RBRi]

Fixed in SVN, thanks for reporting ;-)