I'd like to introduce kSynthetic type of nodes for Heap Profiler.

src/profile-generator.cc

 // 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 1113 matching lines @@
   switch (type()) {
     case kHidden: return "/hidden/";
     case kObject: return "/object/";
     case kClosure: return "/closure/";
     case kString: return "/string/";
     case kCode: return "/code/";
     case kArray: return "/array/";
     case kRegExp: return "/regexp/";
     case kHeapNumber: return "/number/";
     case kNative: return "/native/";
+    case kArtificial: return "/artificial/";
     default: return "???";
   }
 }
 
 
 int HeapEntry::EntriesSize(int entries_count,
                            int children_count,
                            int retainers_count) {
   return sizeof(HeapEntry) * entries_count         // NOLINT
       + sizeof(HeapGraphEdge) * children_count     // NOLINT
@@ skipping 1587 matching lines @@
 }
 
 
 HeapEntry* NativeObjectsExplorer::AllocateEntry(
     HeapThing ptr, int children_count, int retainers_count) {
   v8::RetainedObjectInfo* info =
       reinterpret_cast<v8::RetainedObjectInfo*>(ptr);
   intptr_t elements = info->GetElementCount();
   intptr_t size = info->GetSizeInBytes();
   return snapshot_->AddEntry(
-      HeapEntry::kNative,
+      static_cast<HeapEntry::Type>(info->GetType()),
       elements != -1 ?
           collection_->names()->GetFormatted(
               "%s / %" V8_PTR_PREFIX "d entries",
               info->GetLabel(),
               info->GetElementCount()) :
           collection_->names()->GetCopy(info->GetLabel()),
       HeapObjectsMap::GenerateId(info),
       size != -1 ? static_cast<int>(size) : 0,
       children_count,
       retainers_count);
@@ skipping 103 matching lines @@
   virtual void Dispose() {
     CHECK(!disposed_);
     disposed_ = true;
     delete this;
   }
   virtual bool IsEquivalent(RetainedObjectInfo* other) {
     return hash_ == other->GetHash() && !strcmp(label_, other->GetLabel());
   }
   virtual intptr_t GetHash() { return hash_; }
   virtual const char* GetLabel() { return label_; }
+  virtual HeapGraphNode::Type GetType() const {
+    return HeapGraphNode::kArtificial;
+  }
 
  private:
   bool disposed_;
   intptr_t hash_;
   const char* label_;
 };
 
 
 NativeGroupRetainedObjectInfo* NativeObjectsExplorer::FindOrAddGroupInfo(
     const char* label) {
@@ skipping 665 matching lines @@
     "," JSON_S("types") ":" JSON_A(
         JSON_A(
             JSON_S("hidden")
             "," JSON_S("array")
             "," JSON_S("string")
             "," JSON_S("object")
             "," JSON_S("code")
             "," JSON_S("closure")
             "," JSON_S("regexp")
             "," JSON_S("number")
-            "," JSON_S("native"))
+            "," JSON_S("native")
+            "," JSON_S("artificial"))
         "," JSON_S("string")
         "," JSON_S("number")
         "," JSON_S("number")
         "," JSON_S("number")
         "," JSON_S("number")
         "," JSON_S("number")
         "," JSON_O(
             JSON_S("fields") ":" JSON_A(
                 JSON_S("type")
                 "," JSON_S("name_or_index")
@@ skipping 134 matching lines @@
 
 
 void HeapSnapshotJSONSerializer::SortHashMap(
     HashMap* map, List<HashMap::Entry*>* sorted_entries) {
   for (HashMap::Entry* p = map->Start(); p != NULL; p = map->Next(p))
     sorted_entries->Add(p);
   sorted_entries->Sort(SortUsingEntryValue);
 }
 
 } }  // namespace v8::internal