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

pkg/compiler/lib/src/cps_ir/cps_ir_tracer.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_tracer;
 
 import 'dart:async' show EventSink;
 import 'cps_ir_nodes.dart' as cps_ir hide Function;
 import '../tracer.dart';
 
@@ skipping 298 matching lines @@
   }
 
   visitCreateInstance(cps_ir.CreateInstance node) {
     String className = node.classElement.name;
     String arguments = node.arguments.map(formatReference).join(', ');
     String typeInformation =
         node.typeInformation.map(formatReference).join(', ');
     return 'CreateInstance $className ($arguments) <$typeInformation>';
   }
 
-  visitIdentical(cps_ir.Identical node) {
-    String left = formatReference(node.left);
-    String right = formatReference(node.right);
-    return "Identical($left, $right)";
-  }
-
   visitInterceptor(cps_ir.Interceptor node) {
     return "Interceptor(${formatReference(node.input)})";
   }
 
   visitCreateFunction(cps_ir.CreateFunction node) {
     return "CreateFunction ${node.definition.element.name}";
   }
 
   visitGetMutableVariable(cps_ir.GetMutableVariable node) {
     String variable = names.name(node.variable.definition);
@@ skipping 265 matching lines @@
   }
 
   visitCreateInstance(cps_ir.CreateInstance node) {
     unexpectedNode(node);
   }
 
   visitIsTrue(cps_ir.IsTrue node) {
     unexpectedNode(node);
   }
 
-  visitIdentical(cps_ir.Identical node) {
-    unexpectedNode(node);
-  }
-
   visitInterceptor(cps_ir.Interceptor node) {
     unexpectedNode(node);
   }
 
   visitReadTypeVariable(cps_ir.ReadTypeVariable node) {
     unexpectedNode(node);
   }
 
   visitReifyRuntimeType(cps_ir.ReifyRuntimeType node) {
     unexpectedNode(node);
@@ skipping 19 matching lines @@
     unexpectedNode(node);
   }
 
   @override
   visitForeignCode(cps_ir.ForeignCode node) {
     if (node.continuation != null) {
       addEdgeToContinuation(node.continuation);
     }
   }
 }