[serializer] prepare attached references for general use.

src/snapshot/code-serializer.h

 // Copyright 2016 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_SNAPSHOT_CODE_SERIALIZER_H_
 #define V8_SNAPSHOT_CODE_SERIALIZER_H_
 
 #include "src/parsing/preparse-data.h"
 #include "src/snapshot/serializer.h"
 
 namespace v8 {
 namespace internal {
 
 class CodeSerializer : public Serializer {
  public:
   static ScriptData* Serialize(Isolate* isolate,
                                Handle<SharedFunctionInfo> info,
                                Handle<String> source);
 
   MUST_USE_RESULT static MaybeHandle<SharedFunctionInfo> Deserialize(
       Isolate* isolate, ScriptData* cached_data, Handle<String> source);
 
-  static const int kSourceObjectIndex = 0;
-  STATIC_ASSERT(kSourceObjectReference == kSourceObjectIndex);
-
-  static const int kCodeStubsBaseIndex = 1;
-
   String* source() const {
     DCHECK(!AllowHeapAllocation::IsAllowed());
     return source_;
   }
 
   const List<uint32_t>* stub_keys() const { return &stub_keys_; }
 
  private:
   CodeSerializer(Isolate* isolate, SnapshotByteSink* sink, String* source)
       : Serializer(isolate, sink), source_(source) {
-    back_reference_map_.AddSourceString(source);
+    reference_map_.AddAttachedReference(source);
   }
 
   ~CodeSerializer() override { OutputStatistics("CodeSerializer"); }
 
   void SerializeObject(HeapObject* o, HowToCode how_to_code,
                        WhereToPoint where_to_point, int skip) override;
 
   void SerializeBuiltin(int builtin_index, HowToCode how_to_code,
                         WhereToPoint where_to_point);
-  void SerializeCodeStub(uint32_t stub_key, HowToCode how_to_code,
+  void SerializeCodeStub(Code* code_stub, HowToCode how_to_code,
                          WhereToPoint where_to_point);
   void SerializeGeneric(HeapObject* heap_object, HowToCode how_to_code,
                         WhereToPoint where_to_point);
-  int AddCodeStubKey(uint32_t stub_key);
 
   DisallowHeapAllocation no_gc_;
   String* source_;
   List<uint32_t> stub_keys_;
   DISALLOW_COPY_AND_ASSIGN(CodeSerializer);
 };
 
 // Wrapper around ScriptData to provide code-serializer-specific functionality.
 class SerializedCodeData : public SerializedData {
  public:
@@ skipping 53 matching lines @@
   static const int kPayloadLengthOffset = kNumCodeStubKeysOffset + kInt32Size;
   static const int kChecksum1Offset = kPayloadLengthOffset + kInt32Size;
   static const int kChecksum2Offset = kChecksum1Offset + kInt32Size;
   static const int kHeaderSize = kChecksum2Offset + kInt32Size;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_SNAPSHOT_CODE_SERIALIZER_H_