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

src/profile-generator.h

Index: src/profile-generator.h
diff --git a/src/profile-generator.h b/src/profile-generator.h
index b88d4659d013cd17104d40b7aaf0f0fab96d943e..5bb05b5832b5ff024373b4e3a56b51e751fb47c1 100644
--- a/src/profile-generator.h
+++ b/src/profile-generator.h
@@ -525,7 +525,8 @@ class HeapEntry BASE_EMBEDDED {
     kClosure = v8::HeapGraphNode::kClosure,
     kRegExp = v8::HeapGraphNode::kRegExp,
     kHeapNumber = v8::HeapGraphNode::kHeapNumber,
-    kNative = v8::HeapGraphNode::kNative
+    kNative = v8::HeapGraphNode::kNative,
+    kArtificial = v8::HeapGraphNode::kArtificial
   };
 
   HeapEntry() { }