Add emulation of transaction retries to memory impl of RunInTransaction.

service/datastore/interface.go

 // 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 datastore
 
 import (
         "golang.org/x/net/context"
 )
 
@@ skipping 124 matching lines @@
         //   - []I where i is some interface type. Each elemet of the slice must
         //     be non-nil, and its underlying type must be either *S or *P.
         //
         // If items in src resolve to Incomplete keys, PutMulti will write the
         // resolved keys back to the items in src.
         PutMulti(src interface{}) error
 
         // DeleteMulti removes items from the datastore.
         DeleteMulti(keys []Key) error
 
+        // Testable returns the Testable interface for the implementation, or nil if
+        // there is none.
+        Testable() Testable
+
         // Raw returns the underlying RawInterface. The Interface and RawInterface may
         // be used interchangably; there's no danger of interleaving access to the
         // datastore via the two.
         Raw() RawInterface
 }