Allow collection of DOM objects in minor GC cycles.

src/global-handles.h

 // Copyright 2011 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 137 matching lines @@
   int NumberOfGlobalHandles() {
     return number_of_global_handles_;
   }
 
   // Clear the weakness of a global handle.
   void ClearWeakness(Object** location);
 
   // Clear the weakness of a global handle.
   void MarkIndependent(Object** location);
 
+  // Mark the reference to this object externaly unreachable.
+  void MarkExternallyUnreachable(Object** location);
+
   static bool IsIndependent(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);
 
   // Process pending weak handles.
   // Returns true if next major GC is likely to collect more garbage.
@@ skipping 111 matching lines @@
 
   friend class Isolate;
 
   DISALLOW_COPY_AND_ASSIGN(GlobalHandles);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_GLOBAL_HANDLES_H_