Make dart2js unittests async.

tests/compiler/dart2js/cpa_inference_test.dart

 // Copyright (c) 2012, 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.
 
 import 'dart:async';
 import "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
 import '../../../sdk/lib/_internal/compiler/implementation/source_file.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/types/types.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/inferrer/concrete_types_inferrer.dart';
@@ skipping 170 matching lines @@
   abstract class Map<K, V> {}
   class Closure {}
   class Type {}
   class StackTrace {}
   class Dynamic_ {}
   bool identical(Object a, Object b) {}
   const proxy = 0;''';
 
 Future<AnalysisResult> analyze(String code, {int maxConcreteTypeSize: 1000}) {
   Uri uri = new Uri(scheme: 'source');
-  MockCompiler compiler = new MockCompiler(
+  MockCompiler compiler = new MockCompiler.internal(
       coreSource: CORELIB,
       enableConcreteTypeInference: true,
       maxConcreteTypeSize: maxConcreteTypeSize);
   compiler.sourceFiles[uri.toString()] =
       new StringSourceFile(uri.toString(), code);
   compiler.typesTask.concreteTypesInferrer.testMode = true;
   return compiler.runCompiler(uri).then((_) {
     return new AnalysisResult(compiler);
   });
 }
@@ skipping 1966 matching lines @@
     testClosures10,
     testClosures11,
     testClosures12,
     testRefinement,
     testDefaultArguments,
     testSuperConstructorCall,
     testSuperConstructorCall2,
     testSuperConstructorCall3,
   ], (f) => f()));
 }