Normalize the object before updating getter/setter info.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 6d86532db578f984a57a100b13371fef2d5a320c..452705744a66e51d43d040731cb7cb6ea8da174c 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -2840,6 +2840,11 @@ Object* JSObject::DefineGetterSetter(String* name,
       if (result.type() == CALLBACKS) {
         Object* obj = result.GetCallbackObject();
         if (obj->IsFixedArray()) {
+          // The object might be in fast mode even though it has
+          // a getter/setter.
+          Object* ok = NormalizeProperties(CLEAR_INOBJECT_PROPERTIES, 0);
+          if (ok->IsFailure()) return ok;
+
           PropertyDetails details = PropertyDetails(attributes, CALLBACKS);
           SetNormalizedProperty(name, obj, details);
           return obj;