Allow hidden properties and implement GetIdentityHash

src/objects.h

 // Copyright 2006-2008 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 1234 matching lines @@
   bool ShouldConvertToSlowElements(int new_capacity);
   // Returns true if the backing storage for the slow-case elements of
   // this object takes up nearly as much space as a fast-case backing
   // storage would.  In that case the JSObject should have fast
   // elements.
   bool ShouldConvertToFastElements();
 
   // Return the object's prototype (might be Heap::null_value()).
   inline Object* GetPrototype();
 
+  // Return the object's hidden properties object. If the object has no hidden
+  // properties and create_if_needed is true, then a new hidden property object
+  // will be allocated. Otherwise the Heap::undefined_value is returned.
+  Object* GetHiddenProperties(bool create_if_needed);
+
   // Tells whether the index'th element is present.
   inline bool HasElement(uint32_t index);
   bool HasElementWithReceiver(JSObject* receiver, uint32_t index);
   bool HasLocalElement(uint32_t index);
 
   bool HasElementWithInterceptor(JSObject* receiver, uint32_t index);
   bool HasElementPostInterceptor(JSObject* receiver, uint32_t index);
 
   Object* SetFastElement(uint32_t index, Object* value);
 
@@ skipping 3043 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_