add weakcallback without persistent copying

src/d8.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 398 matching lines @@
                                             Handle<Object> buffer,
                                             ExternalArrayType type,
                                             int32_t length,
                                             int32_t byteLength,
                                             int32_t byteOffset,
                                             int32_t element_size);
   static Handle<Value> CreateExternalArray(const Arguments& args,
                                            ExternalArrayType type,
                                            int32_t element_size);
   static void ExternalArrayWeakCallback(Isolate* isolate,
-                                        Persistent<Value> object,
-                                        void* data);
+                                        Persistent<Object>* object,
+                                        uint8_t* data);
 };
 
 
 }  // namespace v8
 
 
 #endif  // V8_D8_H_