Need another sign that iTunes will soon be floating your library up to the cloud? Look no further than confirmation of Apple signing Warner Music, a deal that should see the label's music available in its upcoming streaming iTunes service. This is in addition to last week's confirmation that two major labels signed on , though its unclear whether Warner is part of the pair or is, indeed, a third. That might leave only one of the major labels left unsigned -- or maybe Apple's already locked down all four but doesn't want to kiss and tell. Yet.