[Isolates] More handle improvements:

src/handles-inl.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 25 matching lines @@
 
 namespace v8 {
 namespace internal {
 
 template<class T>
 Handle<T>::Handle(T* obj) {
   ASSERT(!obj->IsFailure());
   location_ = HandleScope::CreateHandle(obj, Isolate::Current());
 }
 
+template<class T>
+Handle<T>::Handle(HeapObject* obj) {
+  location_ = HandleScope::CreateHandle<T>(obj, obj->GetIsolate());
+}
+
 
 template<class T>
 Handle<T>::Handle(T* obj, Isolate* isolate) {
   ASSERT(!obj->IsFailure());
   location_ = HandleScope::CreateHandle(obj, isolate);
 }
 
 
 template <class T>
 inline T* Handle<T>::operator*() const {
   ASSERT(location_ != NULL);
   ASSERT(reinterpret_cast<Address>(*location_) != kHandleZapValue);
   return *BitCast<T**>(location_);
 }
 
 
+// Helper class to zero out the number of extensions in the handle
+// scope data after it has been saved.
+// This is only necessary for HandleScope constructor to get the right
+// order of effects.
+class HandleScopeDataTransfer {
+ public:
+  typedef v8::ImplementationUtilities::HandleScopeData Data;
+
+  explicit HandleScopeDataTransfer(Data* data) : data_(data) {}
+  ~HandleScopeDataTransfer() { data_->extensions = 0; }
+
+  // Called before the destructor to get the data to save.
+  Data* data() { return data_; }
+
+ private:
+  Data* data_;
+
+  DISALLOW_COPY_AND_ASSIGN(HandleScopeDataTransfer);
+};
+
+
 HandleScope::HandleScope()
-    : previous_(*Isolate::Current()->handle_scope_data()) {
-  Isolate::Current()->handle_scope_data()->extensions = 0;
+    : previous_(*HandleScopeDataTransfer(
+        Isolate::Current()->handle_scope_data()).data()) {
 }
 
 
+HandleScope::HandleScope(Isolate* isolate)
+    : previous_(*HandleScopeDataTransfer(isolate->handle_scope_data()).data()) {
+  ASSERT(isolate == Isolate::Current());
+}
+
+
 template <typename T>
 T** HandleScope::CreateHandle(T* value, Isolate* isolate) {
   ASSERT(isolate == Isolate::Current());
   v8::ImplementationUtilities::HandleScopeData* current =
       isolate->handle_scope_data();
 
   internal::Object** cur = current->next;
   if (cur == current->limit) cur = Extend();
   // Update the current next field, set the value in the created
   // handle, and return the result.
@@ skipping 46 matching lines @@
   // Restore state in current handle scope to re-enable handle
   // allocations.
   Isolate::Current()->handle_scope_data()->extensions = extensions_;
 }
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_INL_H_