Eagerly follow transitions to existing maps while json parsing.

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1603 matching lines @@
       PropertyAttributes attributes,
       StrictModeFlag strict_mode,
       ExtensibilityCheck extensibility_check);
 
   static Handle<Object> SetLocalPropertyIgnoreAttributes(
       Handle<JSObject> object,
       Handle<String> key,
       Handle<Object> value,
       PropertyAttributes attributes);
 
+  // Try to follow an existing transition to a field with attributes NONE. The
+  // return value indicates whether the transition was successful.
+  inline bool TryTransitionToField(String* key);

[danno, 2012/10/17 13:54:23]

must be static and use Handle<> just like other Handle APIs

[Toon Verwaest, 2012/10/17 14:03:40]

Done.

+
+  // 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);
+  inline MUST_USE_RESULT MaybeObject* AddFastPropertyUsingMap(Map* map);
+
   // Can cause GC.
   MUST_USE_RESULT MaybeObject* SetLocalPropertyIgnoreAttributes(
       String* key,
       Object* value,
       PropertyAttributes attributes);
 
   // Retrieve a value in a normalized object given a lookup result.
   // Handles the special representation of JS global objects.
   Object* GetNormalizedProperty(LookupResult* result);
 
@@ skipping 7298 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_