Implemented really weak handles.

src/global-handles.h

 // Copyright 2007-2008 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 53 matching lines @@
 
   // Make the global handle weak and set the callback parameter for the
   // handle.  When the garbage collector recognizes that only weak global
   // handles point to an object the handles are cleared and the callback
   // function is invoked (for each handle) with the handle and corresponding
   // parameter as arguments.  Note: cleared means set to Smi::FromInt(0). The
   // reason is that Smi::FromInt(0) does not change during garage collection.
   static void MakeWeak(Object** location,
                        void* parameter,
                        WeakReferenceCallback callback);
+  static void MakeReallyWeak(Object** location,
+                             void* parameter,
+                             WeakReferenceCallback callback);
 
   // Returns the current number of weak handles.
   static int NumberOfWeakHandles() { return number_of_weak_handles_; }
 
-  // Returns the current number of weak handles to global objects.
-  // These handles are also included in NumberOfWeakHandles().
-  static int NumberOfGlobalObjectWeakHandles() {
-    return number_of_global_object_weak_handles_;
-  }
-
   // Clear the weakness of a global handle.
   static void ClearWeakness(Object** location);
 
   // Tells whether global handle is near death.
   static bool IsNearDeath(Object** location);
 
   // Tells whether global handle is weak.
   static bool IsWeak(Object** location);
 
+  // Tells whether global handle is really weak.
+  static bool IsReallyWeak(Object** location);
+
   // Process pending weak handles.
   static void PostGarbageCollectionProcessing();
 
   // Iterates over all handles.
   static void IterateRoots(ObjectVisitor* v);
 
   // Iterates over all weak roots in heap.
   static void IterateWeakRoots(ObjectVisitor* v);
 
   // Find all weak handles satisfying the callback predicate, mark
@@ skipping 18 matching lines @@
   static void PrintStats();
   static void Print();
 #endif
  private:
   // Internal node structure, one for each global handle.
   class Node;
 
   // Field always containing the number of weak and near-death handles.
   static int number_of_weak_handles_;
 
-  // Field always containing the number of weak and near-death handles
-  // to global objects.  These objects are also included in
-  // number_of_weak_handles_.
-  static int number_of_global_object_weak_handles_;
-
   // Global handles are kept in a single linked list pointed to by head_.
   static Node* head_;
   static Node* head() { return head_; }
   static void set_head(Node* value) { head_ = value; }
 
   // Free list for DESTROYED global handles not yet deallocated.
   static Node* first_free_;
   static Node* first_free() { return first_free_; }
   static void set_first_free(Node* value) { first_free_ = value; }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_GLOBAL_HANDLES_H_