External references should not affect dominance relation.

src/profile-generator-inl.h

Index: src/profile-generator-inl.h
diff --git a/src/profile-generator-inl.h b/src/profile-generator-inl.h
index 65369befdfa8fa710eecf09a2e174f64fec214b2..3e82353fec3cade52884a0abe6290acd3e3a42cf 100644
--- a/src/profile-generator-inl.h
+++ b/src/profile-generator-inl.h
@@ -95,6 +95,11 @@ CodeEntry* ProfileGenerator::EntryForVMState(StateTag tag) {
 }
 
 
+HeapEntry* HeapGraphEdge::from() {
+  return reinterpret_cast<HeapEntry*>(this - child_index_) - 1;
+}
+
+
 SnapshotObjectId HeapObjectsMap::GetNthGcSubrootId(int delta) {
   return kGcRootsFirstSubrootId + delta * kObjectIdStep;
 }