Use closure conversion in new dart2js backend.

pkg/compiler/lib/src/js_emitter/new_emitter/emitter.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.new_js_emitter.emitter;
 
 import '../model.dart';
 import 'model_emitter.dart';
 import '../../common.dart';
 import '../../elements/elements.dart' show FieldElement;
@@ skipping 116 matching lines @@
   }
 
   @override
   js.Expression typeAccess(Element element) {
     // TODO(floitsch): minify 'ensureResolved'.
     // TODO(floitsch): don't emit `ensureResolved` for eager classes.
     return js.js('#.ensureResolved()', _globalPropertyAccess(element));
   }
 
   @override
+  js.PropertyAccess closureClassConstructorAccess(ClassElement element) {
+    return _globalPropertyAccess(element);
+  }
+
+  @override
   void invalidateCaches() {}
 }