Refactor embedded pointer visitors for the serializer

src/objects.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 7872 matching lines @@
   virtual void VisitPointer(Object** p) { VisitPointers(p, p + 1); }
 
   // Visit pointer embedded into a code object.
   virtual void VisitEmbeddedPointer(RelocInfo* rinfo);
 
   // Visits a contiguous arrays of external references (references to the C++
   // heap) in the half-open range [start, end). Any or all of the values
   // may be modified on return.
   virtual void VisitExternalReferences(Address* start, Address* end) {}
 
+  virtual void VisitExternalReference(RelocInfo* rinfo);
+
   inline void VisitExternalReference(Address* p) {
     VisitExternalReferences(p, p + 1);
   }
 
   // Visits a handle that has an embedder-assigned class ID.
   virtual void VisitEmbedderReference(Object** p, uint16_t class_id) {}
 
 #ifdef DEBUG
   // Intended for serialization/deserialization checking: insert, or
   // check for the presence of, a tag at this position in the stream.
@@ skipping 35 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_