StreamingFetcher is now just Fetcher, and its FetchStreaming is now
just Fetch.
SeekFetcher is gone. Blobs are max 16 MB anyway, so we can slurp to
memory when needed. The main thing that cared about SeekFetcher
was the GET handler, ServeBlobref, because http.ServeContent needed
one for range requests. That's rewritten in an earlier commit, using
the FakeSeeker from another earlier commit.
Lot of code got simpler as a result.
Change-Id: Ib819413e48a8f9b8d97f596d0fbf771dab211f11
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
Brad Fitzpatrick