Implemented really weak handles.

src/global-handles.h

Index: src/global-handles.h
diff --git a/src/global-handles.h b/src/global-handles.h
index 9e63ba7a9730fa146780b7dc85f2a59b355b8b17..2afd67a4bbcbaaa8ad2d06c805d96c3854c18bd2 100644
--- a/src/global-handles.h
+++ b/src/global-handles.h
@@ -71,16 +71,13 @@ class GlobalHandles : public AllStatic {
   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);
 
@@ -90,6 +87,9 @@ class GlobalHandles : public AllStatic {
   // 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();
 
@@ -128,11 +128,6 @@ class GlobalHandles : public AllStatic {
   // 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_; }