[turbofan] Remove locally constructed simplified builders.

src/compiler/simplified-lowering.cc

Index: src/compiler/simplified-lowering.cc
diff --git a/src/compiler/simplified-lowering.cc b/src/compiler/simplified-lowering.cc
index 1a601ec41521df4781b1e7896efd6ff8b4e5b1e5..5c5b4026db3eb47508858c7631dd1ea6716ea403 100644
--- a/src/compiler/simplified-lowering.cc
+++ b/src/compiler/simplified-lowering.cc
@@ -1163,8 +1163,8 @@ SimplifiedLowering::SimplifiedLowering(JSGraph* jsgraph, Zone* zone,
 
 
 void SimplifiedLowering::LowerAllNodes() {
-  SimplifiedOperatorBuilder simplified(graph()->zone());
-  RepresentationChanger changer(jsgraph(), &simplified, jsgraph()->isolate());
+  RepresentationChanger changer(jsgraph(), jsgraph()->simplified(),
+                                jsgraph()->isolate());
   RepresentationSelector selector(jsgraph(), zone_, &changer,
                                   source_positions_);
   selector.Run(this);