Implement PersistentValueMap, a map that stores UniquePersistent values.

src/api.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 542 matching lines @@
 }
 
 
 void V8::MakeWeak(i::Object** object,
                   void* parameters,
                   WeakCallback weak_callback) {
   i::GlobalHandles::MakeWeak(object, parameters, weak_callback);
 }
 
 
-void V8::ClearWeak(i::Object** obj) {
-  i::GlobalHandles::ClearWeakness(obj);
+void* V8::ClearWeak(i::Object** obj) {
+  return i::GlobalHandles::ClearWeakness(obj);
 }
 
 
 void V8::DisposeGlobal(i::Object** obj) {
   i::GlobalHandles::Destroy(obj);
 }
 
 
 void V8::Eternalize(Isolate* v8_isolate, Value* value, int* index) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
@@ skipping 6767 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal