Don't create new maps in CurrentMapForDeprecated.

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index d697da7bda41a7cda38a6f510044edbd4eddc8ec..ad7b119854dad4cc67ce5fd92f84d798bf08af94 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -278,7 +278,9 @@ class SmallMapList {
   int length() const { return list_.length(); }
 
   void AddMapIfMissing(Handle<Map> map, Zone* zone) {
-    map = Map::CurrentMapForDeprecated(map);
+    Map* updated = map->CurrentMapForDeprecated();
+    if (updated == NULL) return;
+    map = Handle<Map>(updated);
     for (int i = 0; i < length(); ++i) {
       if (at(i).is_identical_to(map)) return;
     }