FormData with sliced Blob

Hi,

I have questions regarding sending FormData with sliced files. When we send
a FormData with a regular file, we send out the multipart data for this
file, like the following:

   ------SomeBoundary...
   Content-Disposition: form-data; name="file"; filename="test.js"
   Content-Type: application/x-javascript
   ...

However, when it is sliced into a blob, it does not have the file name and
type information any more. I am wondering what we should send.  Should we
just not provide the filename and Content-Type information?

Thanks,

Jian