[Isolates] More handle improvements:

src/handles.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 26 matching lines @@
 // A Handle provides a reference to an object that survives relocation by
 // the garbage collector.
 // Handles are only valid within a HandleScope.
 // When a handle is created for an object a cell is allocated in the heap.
 
 template<class T>
 class Handle {
  public:
   INLINE(explicit Handle(T** location)) { location_ = location; }
   INLINE(explicit Handle(T* obj));
+  INLINE(explicit Handle(HeapObject* obj));
   INLINE(Handle(T* obj, Isolate* isolate));
 
   INLINE(Handle()) : location_(NULL) {}
 
   // Constructor for handling automatic up casting.
   // Ex. Handle<JSFunction> can be passed when Handle<Object> is expected.
   template <class S> Handle(Handle<S> handle) {
 #ifdef DEBUG
     T* a = NULL;
     S* b = NULL;
@@ skipping 45 matching lines @@
 // place in the new handle scope until it is deleted.  After that,
 // new handles will again be allocated in the original handle scope.
 //
 // After the handle scope of a local handle has been deleted the
 // garbage collector will no longer track the object stored in the
 // handle and may deallocate it.  The behavior of accessing a handle
 // for which the handle scope has been deleted is undefined.
 class HandleScope {
  public:
   inline HandleScope();
+  explicit inline HandleScope(Isolate* isolate);
 
   ~HandleScope() {
     Leave(&previous_);
   }
 
   // Counts the number of allocated handles.
   static int NumberOfHandles();
 
   // Creates a new handle with the given value.
   template <typename T>
@@ skipping 235 matching lines @@
  private:
   bool has_been_transformed_;  // Tells whether the object has been transformed.
   int unused_property_fields_;  // Captures the unused number of field.
   Handle<JSObject> object_;    // The object being optimized.
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_H_