dart2js cps: Make Identical a built-in and add Interceptor to Tree IR.

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 '../constants/values.dart';
 import '../util/util.dart';
 import 'cps_ir_nodes.dart';
 
@@ skipping 281 matching lines @@
     return '(CreateBox)';
   }
 
   String visitCreateInstance(CreateInstance node) {
     String className = node.classElement.name;
     String arguments = node.arguments.map(access).join(' ');
     String typeInformation = node.typeInformation.map(access).join(' ');
     return '(CreateInstance $className ($arguments)$typeInformation)';
   }
 
-  String visitIdentical(Identical node) {
-    String left = access(node.left);
-    String right = access(node.right);
-    return '(Identical $left $right)';
-  }
-
   String visitInterceptor(Interceptor node) {
     return '(Interceptor ${access(node.input)})';
   }
 
   String visitReifyRuntimeType(ReifyRuntimeType node) {
     return '(ReifyRuntimeType ${access(node.value)})';
   }
 
   String visitReadTypeVariable(ReadTypeVariable node) {
     return '(ReadTypeVariable ${access(node.target)}.${node.variable})';
@@ skipping 135 matching lines @@
   void setReturnContinuation(Continuation node) {
     assert(!_names.containsKey(node) || _names[node] == 'return');
     _names[node] = 'return';
   }
 
   String getName(Node node) {
     if (!_names.containsKey(node)) return 'MISSING_NAME';
     return _names[node];
   }
 }