Provide mutators in NodeProperties instead of exposing indicies.

test/cctest/compiler/test-simplified-lowering.cc

Index: test/cctest/compiler/test-simplified-lowering.cc
diff --git a/test/cctest/compiler/test-simplified-lowering.cc b/test/cctest/compiler/test-simplified-lowering.cc
index 4ca5be1d6283a75788c6bb068c433e471625c436..4cdccaab38a78e12a6e246ff344a1aff39f9ae4d 100644
--- a/test/cctest/compiler/test-simplified-lowering.cc
+++ b/test/cctest/compiler/test-simplified-lowering.cc
@@ -708,7 +708,7 @@ class TestingGraph : public HandleAndZoneScope, public GraphAndBuilders {
     Node* tb = graph()->NewNode(common()->IfTrue(), br);
     Node* fb = graph()->NewNode(common()->IfFalse(), br);
     Node* m = graph()->NewNode(common()->Merge(2), tb, fb);
-    ret->ReplaceInput(NodeProperties::FirstControlIndex(ret), m);
+    NodeProperties::ReplaceControlInput(ret, m);
     return br;
   }