Implement PersistentValueMap, a map that stores UniquePersistent values. Part 2.

src/global-handles.h

Index: src/global-handles.h
diff --git a/src/global-handles.h b/src/global-handles.h
index f46a22a1eb2a694e1f5cddbec884b7f57b7e3802..13fc111d8178c80e5cf86e5eae302c00d4f16764 100644
--- a/src/global-handles.h
+++ b/src/global-handles.h
@@ -161,7 +161,7 @@ class GlobalHandles {
   }
 
   // Clear the weakness of a global handle.
-  static void ClearWeakness(Object** location);
+  static void* ClearWeakness(Object** location);
 
   // Clear the weakness of a global handle.
   static void MarkIndependent(Object** location);