gae cloud: Use with Datastore

impl/cloud/context.go

Index: impl/cloud/context.go
diff --git a/impl/cloud/context.go b/impl/cloud/context.go
index a4b19ea6990e1adbece421ee9dc7bafed5d184c6..bd8fa8e1ad82fc977fc6f2109529acf327c4bb8f 100644
--- a/impl/cloud/context.go
+++ b/impl/cloud/context.go
@@ -51,10 +51,7 @@ func (cfg Config) Use(c context.Context) context.Context {
 
 	// datastore service
 	if cfg.DS != nil {
-		cds := cloudDatastore{
-			client: cfg.DS,
-		}
-		c = cds.use(c)
+		c = UseDatastore(c, cfg.DS)
 	} else {
 		c = ds.SetRaw(c, dummy.Datastore())
 	}
@@ -71,3 +68,11 @@ func (cfg Config) Use(c context.Context) context.Context {
 
 	return c
 }
+
+// UseDatastore installs a datastore implementation into the context.
+func UseDatastore(c context.Context, client *datastore.Client) context.Context {
+	cds := cloudDatastore{
+		client: client,
+	}
+	return cds.use(c)
+}