External references should not affect dominance relation.

src/profile-generator-inl.h

 // Copyright 2010 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 77 matching lines @@
     // To avoid confusing people, let's put all these entries into
     // one bucket.
     case OTHER:
     case EXTERNAL:
       return program_entry_;
     default: return NULL;
   }
 }
 
 
+HeapEntry* HeapGraphEdge::from() {
+  return reinterpret_cast<HeapEntry*>(this - child_index_) - 1;
+}
+
+
 SnapshotObjectId HeapObjectsMap::GetNthGcSubrootId(int delta) {
   return kGcRootsFirstSubrootId + delta * kObjectIdStep;
 }
 
 
 HeapObject* V8HeapExplorer::GetNthGcSubrootObject(int delta) {
   return reinterpret_cast<HeapObject*>(
       reinterpret_cast<char*>(kFirstGcSubrootObject) +
       delta * HeapObjectsMap::kObjectIdStep);
 }
 
 
 int V8HeapExplorer::GetGcSubrootOrder(HeapObject* subroot) {
   return static_cast<int>(
       (reinterpret_cast<char*>(subroot) -
        reinterpret_cast<char*>(kFirstGcSubrootObject)) /
       HeapObjectsMap::kObjectIdStep);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_PROFILE_GENERATOR_INL_H_