add weakcallback without persistent copying

src/d8.cc

 // 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 1044 matching lines @@
       for (int i = 0; i < source_length; ++i)
         self->Set(offset + i, source->Get(i));
     }
   }
 
   return Undefined(args.GetIsolate());
 }
 
 
 void Shell::ExternalArrayWeakCallback(v8::Isolate* isolate,
-                                      Persistent<Value> object,
-                                      void* data) {
+                                      Persistent<Object>* object,
+                                      uint8_t* data) {
   HandleScope scope(isolate);
-  int32_t length = object->ToObject()->Get(
+  int32_t length = (*object)->Get(
       PerIsolateData::byteLength_string(isolate))->Uint32Value();
   isolate->AdjustAmountOfExternalAllocatedMemory(-length);
-  delete[] static_cast<uint8_t*>(data);
-  object.Dispose(isolate);
+  delete[] data;
+  object->Dispose(isolate);
 }
 
 
 Handle<Value> Shell::Int8Array(const Arguments& args) {
   return CreateExternalArray(args, v8::kExternalByteArray, sizeof(int8_t));
 }
 
 
 Handle<Value> Shell::Uint8Array(const Arguments& args) {
   return CreateExternalArray(args, kExternalUnsignedByteArray, sizeof(uint8_t));
@@ skipping 1152 matching lines @@
 }
 
 }  // namespace v8
 
 
 #ifndef GOOGLE3
 int main(int argc, char* argv[]) {
   return v8::Shell::Main(argc, argv);
 }
 #endif