datastore: Update AllocateIDs to take keys.

filter/count/rds.go

Index: filter/count/rds.go
diff --git a/filter/count/rds.go b/filter/count/rds.go
index 69e903aea911634fca022ddd4881380048793255..33bfef701a65af6a3ab8a30eee58676e06552087 100644
--- a/filter/count/rds.go
+++ b/filter/count/rds.go
@@ -30,9 +30,8 @@ type dsCounter struct {
 
 var _ ds.RawInterface = (*dsCounter)(nil)
 
-func (r *dsCounter) AllocateIDs(incomplete *ds.Key, n int) (int64, error) {
-	start, err := r.ds.AllocateIDs(incomplete, n)
-	return start, r.c.AllocateIDs.up(err)
+func (r *dsCounter) AllocateIDs(keys []*ds.Key) error {
+	return r.c.AllocateIDs.up(r.ds.AllocateIDs(keys))
 }
 
 func (r *dsCounter) DecodeCursor(s string) (ds.Cursor, error) {