Serializer: serialize internal references via object visitor.

src/serialize.h

Index: src/serialize.h
diff --git a/src/serialize.h b/src/serialize.h
index ca748a7e339aa2fd8f8d916e589e1ac8d72e4b9f..e4d6906ceac6cc1097311a5f055c434681b878b2 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -307,7 +307,7 @@ class SerializerDeserializer: public ObjectVisitor {
   enum Where {
     kNewObject = 0,  //              Object is next in snapshot.
     // 1-7                           One per space.
-    // 0x8                           Unused.
+    // 0x8                           Used by misc. See below.
     kRootArray = 0x9,             // Object is found in root array.
     kPartialSnapshotCache = 0xa,  // Object is in the cache.
     kExternalReference = 0xb,     // Pointer to an external reference.
@@ -355,6 +355,11 @@ class SerializerDeserializer: public ObjectVisitor {
   // These autoadvance the current pointer.
   static const int kOnePointerRawData = 0x21;
 
+  // Internal reference encoded as relative offset.
+  static const int kInternalReference = 0x08;
+
+  // 0x48, 0x88 and 0xc8 are unused.
+
   static const int kVariableRepeat = 0x60;
   // 0x61-0x6f   Repeat last word
   static const int kFixedRepeat = 0x61;
@@ -626,6 +631,7 @@ class Serializer : public SerializerDeserializer {
     void VisitEmbeddedPointer(RelocInfo* target);
     void VisitExternalReference(Address* p);
     void VisitExternalReference(RelocInfo* rinfo);
+    void VisitInternalReference(RelocInfo* rinfo);
     void VisitCodeTarget(RelocInfo* target);
     void VisitCodeEntry(Address entry_address);
     void VisitCell(RelocInfo* rinfo);