Add zapping of disposed persistent handles.

R=svenpanne@chromium.org
BUG=chromium:176056

Review URL: https://codereview.chromium.org/12260060

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13675 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/global-handles.cc

@@ -113,6 +113,15 @@ class GlobalHandles::Node {
   void Release(GlobalHandles* global_handles) {
     ASSERT(state() != FREE);
     set_state(FREE);
+#ifdef DEBUG
+    // Zap the values for eager trapping.
+    object_ = NULL;
+    class_id_ = v8::HeapProfiler::kPersistentHandleNoClassId;
+    set_independent(false);
+    set_partially_dependent(false);
+    weak_reference_callback_ = NULL;
+    near_death_callback_ = NULL;
+#endif
     parameter_or_next_free_.next_free = global_handles->first_free_;
     global_handles->first_free_ = this;
     DecreaseBlockUses(global_handles);