Allow users of the V8 API to distinguish between unset and undefined HiddenValues

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 3917 matching lines @@
 v8::Local<v8::Value> v8::Object::GetHiddenValue(v8::Handle<v8::String> key) {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   ON_BAILOUT(isolate, "v8::Object::GetHiddenValue()",
              return Local<v8::Value>());
   ENTER_V8(isolate);
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
   i::Handle<i::String> key_obj = Utils::OpenHandle(*key);
   i::Handle<i::String> key_string =
       isolate->factory()->InternalizeString(key_obj);
   i::Handle<i::Object> result(self->GetHiddenProperty(*key_string), isolate);
-  if (result->IsUndefined()) return v8::Local<v8::Value>();
+  if (result->IsTheHole()) return v8::Local<v8::Value>();
   return Utils::ToLocal(result);
 }
 
 
 bool v8::Object::DeleteHiddenValue(v8::Handle<v8::String> key) {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   ON_BAILOUT(isolate, "v8::DeleteHiddenValue()", return false);
   ENTER_V8(isolate);
   i::HandleScope scope(isolate);
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
@@ skipping 4042 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);
   return callback(info);
 }
 
 
 } }  // namespace v8::internal