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

include/v8-profiler.h

Index: include/v8-profiler.h
diff --git a/include/v8-profiler.h b/include/v8-profiler.h
index bcca65edbcab607196694d06e15b2464828f5253..61b13b81f632cc5bba1b092552b0a9bab47bc657 100644
--- a/include/v8-profiler.h
+++ b/include/v8-profiler.h
@@ -255,7 +255,11 @@ class V8EXPORT HeapGraphNode {
     kClosure = 5,     // Function closure.
     kRegExp = 6,      // RegExp.
     kHeapNumber = 7,  // Number stored in the heap.
-    kNative = 8       // Native object (not from V8 heap).
+    kNative = 8,      // Native object (not from V8 heap).
+    kArtificial = 9   // Artificial object, usualy used for grouping

[mnaganov (inactive), 2012/02/06 12:23:00]

I'd rename this to kVirtual, as virtual is something that can be perceived, but
isn't physically exist.

And I'd remove too specific description and rephrase the comment like this:
"Virtual node, typically used for grouping other nodes together."

"Artificial node, introduced for grouping purposes

[mnaganov (inactive), 2012/02/06 12:23:00]

Also, let's convert existing virtual nodes -- the global root, GC root and
subroots into this type. Better to be done as a separate CL.

+                      // snapshot items together for reducing
+                      // postprocessing steps.
+                      // example - group of detached DOM trees.
   };
 
   /** Returns node type (see HeapGraphNode::Type). */
@@ -501,6 +505,9 @@ class V8EXPORT RetainedObjectInfo {  // NOLINT
   /** Returns embedder's object size in bytes. */
   virtual intptr_t GetSizeInBytes() { return -1; }
 
+  /** Returns embedder's object type. */
+  virtual HeapGraphNode::Type GetType() const { return HeapGraphNode::kNative; }

[mnaganov (inactive), 2012/02/06 12:23:00]

I'm strongly against adding this method. It's only needed for your
implementation, and creates confusion. Please re-consider your implementation to
avoid it.

+
  protected:
   RetainedObjectInfo() {}
   virtual ~RetainedObjectInfo() {}