--- old/src/share/vm/memory/iterator.hpp	2017-04-11 12:39:03.040807549 +0200
+++ new/src/share/vm/memory/iterator.hpp	2017-04-11 12:39:02.900802030 +0200
@@ -65,6 +65,16 @@
  public:
   ReferenceProcessor* ref_processor() const { return _ref_processor; }
 
+  // Iteration of InstanceRefKlasses differ depending on the closure,
+  // the below enum describes the different alternatives.
+  enum ReferenceIterationMode {
+    DO_DISCOVERY, // Tries to discover references
+    DO_FIELDS     // No discovery, just apply closure to all fields
+  };
+
+  // The current default iteration mode is to do discovery.
+  virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERY; }
+
   // If the do_metadata functions return "true",
   // we invoke the following when running oop_iterate():
   //