Refactor a bit.

service/blobstore/types.go

Index: service/blobstore/types.go
diff --git a/service/blobstore/types.go b/service/blobstore/types.go
new file mode 100644
index 0000000000000000000000000000000000000000..a2ce44e0e46981b4bc2c7d913e1fd9ff27e2b434
--- /dev/null
+++ b/service/blobstore/types.go
@@ -0,0 +1,16 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package blobstore
+
+// Key is a key for a blobstore blob.
+//
+// Conceptually, this type belongs in the blobstore package, but it lives in the
+// appengine package to avoid a circular dependency: blobstore depends on
+// datastore, and datastore needs to refer to the Key type.
+//
+// Blobstore is NOT YET supported by gae, but may be supported later. Its
+// inclusion here is so that the RawDatastore can interact (and round-trip)
+// correctly with other datastore API implementations.
+type Key string