sync: Specialize functions that fetch type root

sync/syncable/nigori_util.cc

Index: sync/syncable/nigori_util.cc
diff --git a/sync/syncable/nigori_util.cc b/sync/syncable/nigori_util.cc
index 5463140ac70d3f262da56a199a935a853f989b07..63dbcac9ee55dcffc356e0778bedfb1df6bd9d11 100644
--- a/sync/syncable/nigori_util.cc
+++ b/sync/syncable/nigori_util.cc
@@ -100,8 +100,7 @@ bool VerifyDataTypeEncryptionForTest(
     NOTREACHED();
     return true;
   }
-  std::string type_tag = ModelTypeToRootTag(type);
-  Entry type_root(trans, GET_BY_SERVER_TAG, type_tag);
+  Entry type_root(trans, GET_TYPE_ROOT, type);
   if (!type_root.good()) {
     NOTREACHED();
     return false;