[turbofan] Ensure that NTLs are always properly connected to the end.

test/unittests/compiler/graph-unittest.h

Index: test/unittests/compiler/graph-unittest.h
diff --git a/test/unittests/compiler/graph-unittest.h b/test/unittests/compiler/graph-unittest.h
index 217c44db1a24950e14f17141fad8e7683b81ba3b..af07c93a75c6d4b5b02410f4769fe2b1ee899691 100644
--- a/test/unittests/compiler/graph-unittest.h
+++ b/test/unittests/compiler/graph-unittest.h
@@ -50,6 +50,7 @@ class GraphTest : public TestWithContext, public TestWithIsolateAndZone {
 
   Matcher<Node*> IsFalseConstant();
   Matcher<Node*> IsTrueConstant();
+  Matcher<Node*> IsUndefinedConstant();
 
   CommonOperatorBuilder* common() { return &common_; }
   Graph* graph() { return &graph_; }