cps-ir: Add support for intercepted calls.

pkg/compiler/lib/src/cps_ir/cps_ir_nodes_sexpr.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 dart2js.ir_nodes_sexpr;
 
 import '../util/util.dart';
 import 'cps_ir_nodes.dart';
 
 /// A [Decorator] is a function used by [SExpressionStringifier] to augment the
@@ skipping 211 matching lines @@
   String visitIsTrue(IsTrue node) {
     String value = access(node.value);
     return '(IsTrue $value)';
   }
 
   String visitIdentical(Identical node) {
     String left = access(node.left);
     String right = access(node.right);
     return '(Identical $left $right)';
   }
+
+  String visitInterceptor(Interceptor node) {
+    return '(Interceptor ${node.input})';
+  }
 }
 
 class _Namer {
   final Map<Node, String> _names = <Node, String>{};
   int _valueCounter = 0;
   int _continuationCounter = 0;
 
   String useElementName(Parameter parameter) {
     assert(!_names.containsKey(parameter));
     return _names[parameter] = parameter.hint.name;
@@ skipping 17 matching lines @@
   String useReturnName(Continuation node) {
     assert(!_names.containsKey(node) || _names[node] == 'return');
     return _names[node] = 'return';
   }
 
   String getName(Node node) {
     assert(_names.containsKey(node));
     return _names[node];
   }
 }