Current schema of calculation max_snapshot_js_object_id is not always correct.

src/profile-generator.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 627 matching lines @@
   HeapSnapshotsCollection* collection() { return collection_; }
   Type type() { return type_; }
   const char* title() { return title_; }
   unsigned uid() { return uid_; }
   HeapEntry* root() { return root_entry_; }
   HeapEntry* gc_roots() { return gc_roots_entry_; }
   HeapEntry* natives_root() { return natives_root_entry_; }
   HeapEntry* gc_subroot(int index) { return gc_subroot_entries_[index]; }
   List<HeapEntry*>* entries() { return &entries_; }
   size_t raw_entries_size() { return raw_entries_size_; }
+  void RememberLastJSObjectId();
   SnapshotObjectId max_snapshot_js_object_id() const {
     return max_snapshot_js_object_id_;
   }
 
   void AllocateEntries(
       int entries_count, int children_count, int retainers_count);
   HeapEntry* AddEntry(HeapEntry::Type type,
                       const char* name,
                       SnapshotObjectId id,
                       int size,
@@ skipping 39 matching lines @@
 
 
 class HeapObjectsMap {
  public:
   HeapObjectsMap();
   ~HeapObjectsMap();
 
   void SnapshotGenerationFinished();
   SnapshotObjectId FindObject(Address addr);
   void MoveObject(Address from, Address to);
+  SnapshotObjectId last_assigned_id() const {
+    return next_id_ - kObjectIdStep;
+  }
 
   static SnapshotObjectId GenerateId(v8::RetainedObjectInfo* info);
   static inline SnapshotObjectId GetNthGcSubrootId(int delta);
 
   static const int kObjectIdStep = 2;
   static const SnapshotObjectId kInternalRootObjectId;
   static const SnapshotObjectId kGcRootsObjectId;
   static const SnapshotObjectId kNativesRootObjectId;
   static const SnapshotObjectId kGcRootsFirstSubrootId;
   static const SnapshotObjectId kFirstAvailableObjectId;
@@ skipping 44 matching lines @@
   List<HeapSnapshot*>* snapshots() { return &snapshots_; }
   HeapSnapshot* GetSnapshot(unsigned uid);
   void RemoveSnapshot(HeapSnapshot* snapshot);
 
   StringsStorage* names() { return &names_; }
   TokenEnumerator* token_enumerator() { return token_enumerator_; }
 
   SnapshotObjectId GetObjectId(Address addr) { return ids_.FindObject(addr); }
   Handle<HeapObject> FindHeapObjectById(SnapshotObjectId id);
   void ObjectMoveEvent(Address from, Address to) { ids_.MoveObject(from, to); }
+  SnapshotObjectId last_assigned_id() const {
+    return ids_.last_assigned_id();
+  }
 
  private:
   INLINE(static bool HeapSnapshotsMatch(void* key1, void* key2)) {
     return key1 == key2;
   }
 
   bool is_tracking_objects_;  // Whether tracking object moves is needed.
   List<HeapSnapshot*> snapshots_;
   // Mapping from snapshots' uids to HeapSnapshot* pointers.
   HashMap snapshots_uids_;
@@ skipping 377 matching lines @@
 
   friend class HeapSnapshotJSONSerializerEnumerator;
   friend class HeapSnapshotJSONSerializerIterator;
 
   DISALLOW_COPY_AND_ASSIGN(HeapSnapshotJSONSerializer);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_PROFILE_GENERATOR_H_