[turbofan] Remove unused PlainPrimitiveToNumber operator.

src/compiler/js-typed-lowering.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/code-factory.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/linkage.h"
@@ skipping 229 matching lines @@
         frame_state->InputAt(kFrameStateContextInput),
         frame_state->InputAt(kFrameStateFunctionInput),
         frame_state->InputAt(kFrameStateOuterStateInput));
   }
 
   Node* ConvertPlainPrimitiveToNumber(Node* node) {
     DCHECK(NodeProperties::GetType(node)->Is(Type::PlainPrimitive()));
     // Avoid inserting too many eager ToNumber() operations.
     Reduction const reduction = lowering_->ReduceJSToNumberInput(node);
     if (reduction.Changed()) return reduction.replacement();
-    // TODO(jarin) Use PlainPrimitiveToNumber once we have it.
     return graph()->NewNode(
         javascript()->ToNumber(), node, jsgraph()->NoContextConstant(),
         jsgraph()->EmptyFrameState(), graph()->start(), graph()->start());
   }
 
   Node* ConvertSingleInputToNumber(Node* node, Node* frame_state) {
     DCHECK(!NodeProperties::GetType(node)->Is(Type::PlainPrimitive()));
     Node* const n = graph()->NewNode(javascript()->ToNumber(), node, context(),
                                      frame_state, effect(), control());
     NodeProperties::ReplaceUses(node_, node_, node_, n, n);
@@ skipping 1553 matching lines @@
 }
 
 
 CompilationDependencies* JSTypedLowering::dependencies() const {
   return dependencies_;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8