Add CPS IR transformation to make the JavaScript backend specific semantics explicit in the tree.

pkg/compiler/lib/src/tree_ir/tree_ir_builder.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_builder;
 
 import '../dart2jslib.dart' as dart2js;
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../cps_ir/cps_ir_nodes.dart' as cps_ir;
@@ skipping 455 matching lines @@
   Expression visitContinuation(cps_ir.Continuation node) {
     // Until continuations with multiple uses are supported, they are not
     // visited.
     compiler.internalError(compiler.currentElement, 'Unexpected IR node.');
     return null;
   }
 
   Expression visitIsTrue(cps_ir.IsTrue node) {
     return getVariableReference(node.value);
   }
+
+  dart2js.Selector get identicalSelector {
+    return new dart2js.Selector.call('identical', null, 2);
+  }
+
+  Expression visitIdentical(cps_ir.Identical node) {
+    return new InvokeStatic(
+        compiler.identicalFunction,
+        identicalSelector,
+        <Expression>[getVariableReference(node.left),
+                     getVariableReference(node.right)]);
+  }
 }