Add WeakCell support to heap profiler.

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 "include/v8-profiler.h"
 #include "src/base/platform/time.h"
 #include "src/objects.h"
@@ skipping 367 matching lines @@
   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 ExtractBoxReferences(int entry, Box* box);
   void ExtractCellReferences(int entry, Cell* cell);
+  void ExtractWeakCellReferences(int entry, WeakCell* weak_cell);
   void ExtractPropertyCellReferences(int entry, PropertyCell* cell);
   void ExtractAllocationSiteReferences(int entry, AllocationSite* site);
   void ExtractJSArrayBufferReferences(int entry, JSArrayBuffer* buffer);
   void ExtractFixedArrayReferences(int entry, FixedArray* array);
   void ExtractPropertyReferences(JSObject* js_obj, int entry);
   void ExtractAccessorPairProperty(JSObject* js_obj, int entry, Name* key,
                                    Object* callback_obj, int field_offset = -1);
   void ExtractElementReferences(JSObject* js_obj, int entry);
   void ExtractInternalReferences(JSObject* js_obj, int entry);
 
@@ skipping 220 matching lines @@
   friend class HeapSnapshotJSONSerializerIterator;
 
   DISALLOW_COPY_AND_ASSIGN(HeapSnapshotJSONSerializer);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PROFILER_HEAP_SNAPSHOT_GENERATOR_H_