Get the target field index when transitioning.

Review URL: https://chromiumcodereview.appspot.com/11194080

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@12772 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/json-parser.h

@@ -289,7 +289,6 @@ Handle<Object> JsonParser<seq_ascii>::ParseJsonValue() {
 // Parse a JSON object. Position must be right at '{'.
 template <bool seq_ascii>
 Handle<Object> JsonParser<seq_ascii>::ParseJsonObject() {
-  int current_index = 0;
   Handle<Object> prototype;
   Handle<JSFunction> object_constructor(
       isolate()->native_context()->object_function());
@@ -339,11 +338,11 @@ Handle<Object> JsonParser<seq_ascii>::ParseJsonObject() {
           prototype = value;
         } else {
           if (JSObject::TryTransitionToField(json_object, key)) {
-            json_object->FastPropertyAtPut(current_index++, *value);
+            int index = json_object->LastAddedFieldIndex();
+            json_object->FastPropertyAtPut(index, *value);
           } else {
             JSObject::SetLocalPropertyIgnoreAttributes(
                 json_object, key, value, NONE);
-            current_index = json_object->NumberOfLocalProperties();
           }
         }
       }

src/objects-inl.h

@@ -1444,6 +1444,13 @@ bool JSObject::TryTransitionToField(Handle<JSObject> object,
 }
 
 
+int JSObject::LastAddedFieldIndex() {
+  Map* map = this->map();
+  int last_added = map->LastAdded();
+  return map->instance_descriptors()->GetFieldIndex(last_added);
+}
+
+
 ACCESSORS(Oddball, to_string, String, kToStringOffset)
 ACCESSORS(Oddball, to_number, Object, kToNumberOffset)
 

src/objects.h

@@ -1626,6 +1626,8 @@ class JSObject: public JSReceiver {
   static inline bool TryTransitionToField(Handle<JSObject> object,
                                           Handle<String> key);
 
+  inline int LastAddedFieldIndex();
+
   // Extend the receiver with a single fast property appeared first in the
   // passed map. This also extends the property backing store if necessary.
   static void AddFastPropertyUsingMap(Handle<JSObject> object, Handle<Map> map);