As Trudelle proposed in bug 22796, 'pre-downloading' will not be implemented until there is a default download directory in which files will automatically be stored until (if at all) the user picks a final destination for the saved file. This RFE covers the implementation of such a default download directory. I will file a separate bug as dependent on this one to implement 'pre-downloading' in a manner which satisfies even Trudelle :-).

*** This bug has been marked as a duplicate of 7840 ***