Implement the bundles-containing API endpoint.

If it's not going to be used, then it doesn't matter. As it is, it's deliberately wrong, which seems a bit odd. I'd prefer us to use well formed data, even if it's not that important in the current implementation. Perhaps a future implementation might panic with an malformed hash. How about defining a couple of globals:

    var fakeBlobSize, fakeBlobHash = func() (int64, string) {
         b := []byte("fake content")
         h := blobstore.NewHash()
         h.Write(b)
         return int64(len(b)), fmt.Sprintf("%x", h.Sum(nil))
    }()

and then using those in the tests?