8327997: G1: Move G1ScanClosureBase::reference_iteration_mode to subc…

…lass

Reviewed-by: gli, tschatzl, sjohanss

src/hotspot/share/gc/g1/g1OopClosures.hpp

@@ -54,8 +54,6 @@ class G1ScanClosureBase : public BasicOopIterateClosure {
   template <class T>
   inline void handle_non_cset_obj_common(G1HeapRegionAttr const region_attr, T* p, oop const obj);
 public:
-  virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
-
   inline void trim_queue_partially();
 };
 
@@ -68,6 +66,8 @@ class G1ScanCardClosure : public G1ScanClosureBase {
                     size_t& heap_roots_found) :
     G1ScanClosureBase(g1h, pss), _heap_roots_found(heap_roots_found) { }
 
+  virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
+
   template <class T> void do_oop_work(T* p);
   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
   virtual void do_oop(oop* p)       { do_oop_work(p); }