The deferred handes list belongs to the Isolate and not to the

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 8b4e12bc0d38aea0acf9498e49258c7c0964995e..ef33dcb3c0b79493adc7e13941e20dc9d122b49b 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -1055,6 +1055,10 @@ class Isolate {
     date_cache_ = date_cache;
   }
 
+  void IterateDeferredHandles(ObjectVisitor* visitor);
+  void LinkDeferredHandles(DeferredHandles* deferred_handles);
+  void UnlinkDeferredHandles(DeferredHandles* deferred_handles);
+
  private:
   Isolate();
 
@@ -1278,6 +1282,8 @@ class Isolate {
 #undef ISOLATE_FIELD_OFFSET
 #endif
 
+  DeferredHandles* deferred_handles_head_;
+
   friend class ExecutionAccess;
   friend class IsolateInitializer;
   friend class ThreadManager;