When generate snapshot use tags_ instead of class_ to store object ids.

runtime/vm/snapshot.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_SNAPSHOT_H_
 #define VM_SNAPSHOT_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
@@ skipping 461 matching lines @@
   DISALLOW_IMPLICIT_CONSTRUCTORS(BaseWriter);
 };
 
 
 class SnapshotWriter : public BaseWriter {
  public:
   SnapshotWriter(Snapshot::Kind kind, uint8_t** buffer, ReAlloc alloc)
       : BaseWriter(buffer, alloc),
         kind_(kind),
         object_store_(Isolate::Current()->object_store()),
+        class_table_(Isolate::Current()->class_table()),
         forward_list_() {
   }
   ~SnapshotWriter() { }
 
   // Snapshot kind.
   Snapshot::Kind kind() const { return kind_; }
 
   // Finalize the serialized buffer by filling in the header information
   // which comprises of a flag(full/partial snaphot) and the length of
   // serialzed bytes.
   void FinalizeBuffer() {
     BaseWriter::FinalizeBuffer(kind_);
     UnmarkAll();
   }
 
   // Serialize an object into the buffer.
   void WriteObject(RawObject* raw);
 
   void WriteClassId(RawClass* cls);
 
   // Unmark all objects that were marked as forwarded for serializing.
   void UnmarkAll();
 
   // Writes a full snapshot of the Isolate.
   void WriteFullSnapshot();
 
+  uword GetObjectTags(RawObject* raw);
+
  private:
   class ForwardObjectNode : public ZoneAllocated {
    public:
-    ForwardObjectNode(RawObject* raw, RawClass* cls) : raw_(raw), cls_(cls) {}
+    ForwardObjectNode(RawObject* raw, uword tags) : raw_(raw), tags_(tags) {}
     RawObject* raw() const { return raw_; }
-    RawClass* cls() const { return cls_; }
+    uword tags() const { return tags_; }
 
    private:
     RawObject* raw_;
-    RawClass* cls_;
+    uword tags_;
 
     DISALLOW_COPY_AND_ASSIGN(ForwardObjectNode);
   };
 
   intptr_t MarkObject(RawObject* raw, RawClass* cls);
 
   void WriteInlinedObject(RawObject* raw);
 
   ObjectStore* object_store() const { return object_store_; }
 
   Snapshot::Kind kind_;
   ObjectStore* object_store_;  // Object store for common classes.
+  ClassTable* class_table_;  // Class table for the class index to class lookup.
   GrowableArray<ForwardObjectNode*> forward_list_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriter);
 };
 
 
 class ScriptSnapshotWriter : public SnapshotWriter {
  public:
   ScriptSnapshotWriter(uint8_t** buffer, ReAlloc alloc)
       : SnapshotWriter(Snapshot::kScript, buffer, alloc) {
@@ skipping 20 matching lines @@
 
  private:
   SnapshotWriter* writer_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_SNAPSHOT_H_