PERL-867 resynced download.json spec 
PERL-867 resynced download.json spec 

for legacy GridFS, where no filename was set
xdg/mongo-perl-driver,mongodb/mongo-perl-driver,dagolden/mongo-perl-driver,dagolden/mongo-perl-driver,dagolden/mongo-perl-driver,xdg/mongo-perl-driver,dagolden/mongo-perl-driver,mongodb/mongo-perl-driver,xdg/mongo-perl-driver,mongodb/mongo-perl-driver