Fix memory leak caused by treating Code::next_code_link as strong in marker.

src/objects-visiting.h

Index: src/objects-visiting.h
diff --git a/src/objects-visiting.h b/src/objects-visiting.h
index 41e5fd6fd382b342c2506da1545de3add43f646f..6fa82704a5d53e2143747c3c8fa89e1b8b771ecb 100644
--- a/src/objects-visiting.h
+++ b/src/objects-visiting.h
@@ -151,6 +151,10 @@ class StaticVisitorBase : public AllStatic {
 
     return Min(specialization, generic);
   }
+
+  static WeakPointerMode weak_pointer_mode() {
+    return VISIT_WEAK_POINTERS;
+  }
 };
 
 
@@ -420,6 +424,10 @@ class StaticMarkingVisitor : public StaticVisitorBase {
   // code. This will prevent it from being flushed.
   static void MarkInlinedFunctionsCode(Heap* heap, Code* code);
 
+  static WeakPointerMode weak_pointer_mode() {
+    return SKIP_WEAK_POINTERS;
+  }
+
  protected:
   INLINE(static void VisitMap(Map* map, HeapObject* object));
   INLINE(static void VisitCode(Map* map, HeapObject* object));