[api] Prototype WeakRef implementation

src/profiler/heap-snapshot-generator.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_PROFILER_HEAP_SNAPSHOT_GENERATOR_H_
 #define V8_PROFILER_HEAP_SNAPSHOT_GENERATOR_H_
 
 #include <deque>
 #include <unordered_map>
 
@@ skipping 359 matching lines @@
 
   bool ExtractReferencesPass1(int entry, HeapObject* obj);
   bool ExtractReferencesPass2(int entry, HeapObject* obj);
   void ExtractJSGlobalProxyReferences(int entry, JSGlobalProxy* proxy);
   void ExtractJSObjectReferences(int entry, JSObject* js_obj);
   void ExtractStringReferences(int entry, String* obj);
   void ExtractSymbolReferences(int entry, Symbol* symbol);
   void ExtractJSCollectionReferences(int entry, JSCollection* collection);
   void ExtractJSWeakCollectionReferences(int entry,
                                          JSWeakCollection* collection);
+  void ExtractJSWeakRefReferences(int entry,
+                                         JSWeakRef* ref);
   void ExtractContextReferences(int entry, Context* context);
   void ExtractMapReferences(int entry, Map* map);
   void ExtractSharedFunctionInfoReferences(int entry,
                                            SharedFunctionInfo* shared);
   void ExtractScriptReferences(int entry, Script* script);
   void ExtractAccessorInfoReferences(int entry, AccessorInfo* accessor_info);
   void ExtractAccessorPairReferences(int entry, AccessorPair* accessors);
   void ExtractCodeReferences(int entry, Code* code);
   void ExtractCellReferences(int entry, Cell* cell);
   void ExtractWeakCellReferences(int entry, WeakCell* weak_cell);
@@ skipping 232 matching lines @@
   friend class HeapSnapshotJSONSerializerIterator;
 
   DISALLOW_COPY_AND_ASSIGN(HeapSnapshotJSONSerializer);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PROFILER_HEAP_SNAPSHOT_GENERATOR_H_