[turbofan] Improve JSToBoolean typing.

src/compiler/typer.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/bootstrapper.h"
 #include "src/compiler/graph-inl.h"
 #include "src/compiler/graph-reducer.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/node.h"
 #include "src/compiler/node-properties-inl.h"
@@ skipping 1164 matching lines @@
 
 Bounds Typer::Visitor::TypeJSTypeOf(Node* node) {
   return Bounds(Type::None(zone()), Type::InternalizedString(zone()));
 }
 
 
 // JS conversion operators.
 
 
 Bounds Typer::Visitor::TypeJSToBoolean(Node* node) {
-  return Bounds(Type::None(zone()), Type::Boolean(zone()));
+  return TypeUnaryOp(node, ToBoolean);
 }
 
 
 Bounds Typer::Visitor::TypeJSToNumber(Node* node) {
   return TypeUnaryOp(node, ToNumber);
 }
 
 
 Bounds Typer::Visitor::TypeJSToString(Node* node) {
   return TypeUnaryOp(node, ToString);
@@ skipping 896 matching lines @@
         // TODO(rossberg): Do we want some ClampedArray type to express this?
         break;
     }
   }
   return Type::Constant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8