Use closure conversion in new dart2js backend.

pkg/compiler/lib/src/js_backend/codegen/js_tree_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 js_tree_ir_builder;
 
 import '../../tree_ir/tree_ir_builder.dart' show Builder;
 import 'glue.dart' show Glue;
 import '../../dart2jslib.dart' show Selector, InternalErrorFunction;
 import '../../elements/elements.dart';
@@ skipping 30 matching lines @@
   }
 
   Expression visitInterceptor(cps_ir.Interceptor node) {
     Element getInterceptor = _glue.getInterceptorMethod;
     _glue.registerUseInterceptorInCodegen();
     return new InvokeStatic(
         getInterceptor,
         new Selector.fromElement(getInterceptor),
         <Expression>[getVariableReference(node.input)]);
   }
+
+  Expression visitGetField(cps_ir.GetField node) {
+    return new GetField(getVariableReference(node.object), node.field);
+  }
+
+  Statement visitSetField(cps_ir.SetField node) {
+    return new SetField(getVariableReference(node.object),
+                        node.field,
+                        getVariableReference(node.value),
+                        visit(node.body));
+  }
+
+  Expression visitCreateBox(cps_ir.CreateBox node) {
+    return new CreateBox();
+  }
+
+  Expression visitCreateClosureClass(cps_ir.CreateClosureClass node) {
+    return new CreateClosureClass(
+        node.classElement,
+        node.arguments.map(getVariableReference).toList());
+  }
 }