Not just in blob.SizedRef, but in blobserver.Fetch and
blobserver.FetchStreaming, too.
Blobs have a max size of 10-32 MB anyway, and the index.Corpus is now using
uint32 to save memory.
Change-Id: I1172445c2f9463fdaee55bfe0f1218d44be4aa53
Move up a layer to the HTTP. Also, start to remove ContextWrapper
stuff. We've done it differently for App Engine instead, and will do
it differently yet moving forward.
Also add blobserver.Receive and use it in most places, moving checksum
verification up a layer.
Bunch of other cleanup and TODO fixing too.
Much simpler and cleaner.
Change-Id: I12e56c5d4e53bfcf82bdd8fb0b6d57c248ff605c