[serializer] prepare attached references for general use.

src/context-measure.h

 // Copyright 2015 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_CONTEXT_MEASURE_H_
 #define V8_CONTEXT_MEASURE_H_
 
 #include "src/address-map.h"
 #include "src/assert-scope.h"
 #include "src/objects.h"
@@ skipping 11 matching lines @@
   void VisitPointers(Object** start, Object** end) override;
 
  private:
   void MeasureObject(HeapObject* object);
   void MeasureDeferredObjects();
   void MeasureAndRecurse(HeapObject* object);
   bool IsShared(HeapObject* object);
 
   Context* context_;
 
-  BackReferenceMap back_reference_map_;
+  SerializerReferenceMap reference_map_;
   RootIndexMap root_index_map_;
 
   static const int kMaxRecursion = 16;
   int recursion_depth_;
   List<HeapObject*> deferred_objects_;
 
   int count_;
   int size_;
 
   DisallowHeapAllocation no_gc_;
 
   DISALLOW_COPY_AND_ASSIGN(ContextMeasure);
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CONTEXT_MEASURE_H_