Fixed incorrect generalization of types in Map::ReconfigureProperty() introduced in r26667.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index fd35c90e8d39049b7a5153339c697d84d90e6ca3..1842bb60ef050d5595f7441bb91b6e9b163c21a6 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -2815,8 +2815,8 @@ Handle<Map> Map::ReconfigureProperty(Handle<Map> old_map, int modify_index,
             Handle<HeapType> old_field_type =
                 GetFieldType(isolate, old_descriptors, i,
                              old_details.location(), next_representation);
-            old_field_type =
-                GeneralizeFieldType(old_field_type, next_field_type, isolate);
+            next_field_type =
+                GeneralizeFieldType(next_field_type, old_field_type, isolate);
           }
         } else {
           Handle<HeapType> old_field_type =