Move continueWithExpression to IrBuilder.

sdk/lib/_internal/compiler/implementation/cps_ir/cps_ir_nodes.dart

 // Copyright (c) 2013, 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.
 
 // IrNodes are kept in a separate library to have precise control over their
 // dependencies on other parts of the system.
 library dart2js.ir_nodes;
 
 import '../constants/expressions.dart';
 import '../constants/values.dart' as values show ConstantValue;
@@ skipping 265 matching lines @@
 }
 
 /// "as" casts and "is" checks.
 // We might want to turn "is"-checks into a [Primitive] as it can never diverge.
 // But then we need to special-case for is-checks with an erroneous .type as
 // these will throw.
 class TypeOperator extends Expression {
   final Reference receiver;
   final DartType type;
   final Reference continuation;
-  final String operator;
+  // TODO(johnniwinther): Use `Operator` class to encapsule the operator type.
+  final bool isTypeTest;
 
-  TypeOperator(this.operator,
-                Primitive receiver,
-                this.type,
-                Continuation cont)
+  TypeOperator(Primitive receiver,
+               this.type,
+               Continuation cont,
+               {bool this.isTypeTest})
       : this.receiver = new Reference(receiver),
         this.continuation = new Reference(cont) {
-    assert(operator == "is" || operator == "as");
+    assert(isTypeTest != null);
   }
 
+  bool get isTypeCast => !isTypeTest;
+
   accept(Visitor visitor) => visitor.visitTypeOperator(this);
 }
 
 /// Invoke [toString] on each argument and concatenate the results.
 class ConcatenateStrings extends Expression {
   final Reference continuation;
   final List<Reference> arguments;
 
   ConcatenateStrings(Continuation cont, List<Definition> args)
       : continuation = new Reference(cont),
@@ skipping 635 matching lines @@
       release(node.parameters[i]);
     }
   }
 
   void visitIsTrue(IsTrue node) {
     visitReference(node.value);
   }
 
 }