[api] Prototype WeakRef implementation

src/heap/object-stats.h

Index: src/heap/object-stats.h
diff --git a/src/heap/object-stats.h b/src/heap/object-stats.h
index 7d0cfb5a691b275e40d7372016492c4766725d91..9739607125097aefb72142e5c530fa18367c7bcc 100644
--- a/src/heap/object-stats.h
+++ b/src/heap/object-stats.h
@@ -148,6 +148,7 @@ class ObjectStatsCollector {
   void RecordJSFunctionDetails(JSFunction* function);
   void RecordJSObjectDetails(JSObject* object);
   void RecordJSWeakCollectionDetails(JSWeakCollection* obj);
+  void RecordJSWeakRefDetails(JSWeakRef* obj);
   void RecordMapDetails(Map* map);
   void RecordScriptDetails(Script* obj);
   void RecordTemplateInfoDetails(TemplateInfo* obj);