Changed scavenge GC to collect unmodified references

src/global-handles.h

Index: src/global-handles.h
diff --git a/src/global-handles.h b/src/global-handles.h
index 0ee8c20a375adaea6803c11034686b08d806f9d8..4498cac38fdbb1db1095e5ed643bc7b06b69af53 100644
--- a/src/global-handles.h
+++ b/src/global-handles.h
@@ -220,6 +220,10 @@ class GlobalHandles {
   // See the note above.
   void IterateNewSpaceWeakIndependentRoots(ObjectVisitor* v);
 
+  // Identify unmodified objects that are in weak state and marks them partially
+  // independent
+  void IdentifyWeakUnmodifiedObjects(WeakSlotCallback can_skip);
+
   // Iterate over objects in object groups that have at least one object
   // which requires visiting. The callback has to return true if objects
   // can be skipped and false otherwise.