Move continueWithExpression to IrBuilder.

sdk/lib/_internal/compiler/implementation/dart_backend/tree_ir_nodes.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library tree_ir_nodes;
 
 import '../constants/expressions.dart';
 import '../constants/values.dart' as values;
 import '../cps_ir/cps_ir_nodes.dart' as cps_ir;
 import '../dart_types.dart' show DartType, GenericType;
@@ skipping 224 matching lines @@
   final List<LiteralMapEntry> entries;
 
   LiteralMap(this.type, this.entries);
 
   accept(ExpressionVisitor visitor) => visitor.visitLiteralMap(this);
 }
 
 class TypeOperator extends Expression {
   Expression receiver;
   final DartType type;
-  final String operator;
+  final bool isTypeTest;
 
-  TypeOperator(this.receiver, this.type, this.operator) ;
+  TypeOperator(this.receiver, this.type, {bool this.isTypeTest});
 
   accept(ExpressionVisitor visitor) => visitor.visitTypeOperator(this);
+
+  String get operator => isTypeTest ? 'is' : 'as';
 }
 
 /// A conditional expression.
 class Conditional extends Expression {
   Expression condition;
   Expression thenExpression;
   Expression elseExpression;
 
   Conditional(this.condition, this.thenExpression, this.elseExpression);
 
@@ skipping 393 matching lines @@
   visitFunctionDeclaration(FunctionDeclaration node) {
     visitFunctionDefinition(node.definition);
     visitStatement(node.next);
   }
 
   visitExpressionStatement(ExpressionStatement node) {
     visitExpression(node.expression);
     visitStatement(node.next);
   }
 }