Set up a stub pipline for using the new cps-based ir to generate js.

tests/compiler/dart2js/backend_dart/test_helper.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 dart_backend.test_helper;
 
 import 'dart:async';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/dart2jslib.dart';
 import '../../../../pkg/analyzer2dart/test/test_helper.dart';
@@ skipping 13 matching lines @@
     if (element == null) return null;
 
     compiler.mainFunction = element;
     compiler.phase = Compiler.PHASE_RESOLVING;
     compiler.backend.enqueueHelpers(compiler.enqueuer.resolution,
                                     compiler.globalDependencies);
     compiler.processQueue(compiler.enqueuer.resolution, element);
     compiler.world.populate();
     compiler.backend.onResolutionComplete();
 
-    compiler.irBuilder.buildNodes(useNewBackend: true);
+    compiler.irBuilder.buildNodes();
 
     return compiler;
   });
 }
 
 /// Test group using async_helper.
 asyncTester(Group group, RunTest runTest) {
   asyncTest(() => Future.forEach(group.results, runTest));
 }