Our nsFormSubmission and subclasses accepted a third filename argument to
explicitly specify the filename. Since switching from nsIDOMBlob to File in Bug
1085283, we can read out the filename directly from the File. This simplifies
the code, but introduces a change in the way Firefox submits form data to
servers.
Consider the code:
var fd = new FormData();
fd.append("blob1", new Blob(["hi"]), ""); // explicit empty filename as third arg
fd.append("file1", new File(["hi"], "")); // File's name is empty, no third arg.
xhr.send(fd);
Previously, the request body had filename="" in the first case, and filename="blob" in the second.
This patch will change it to both cases result in filename=""
This behaviour isn't exactly specced anywhere, nor in the HTML spec [1], nor in
RFC 2388. In addition Blink (at least Chromium v40) has the same behaviour
introduced by this patch. So shipping it seems ok to me.
[1]: http://www.w3.org/html/wg/drafts/html/master/semantics.html#multipart/form-data-encoding-algorithm
