Make dart2js unittests async.

tests/compiler/dart2js/private_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 "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
 import 'mock_compiler.dart';
 
 import '../../../sdk/lib/_internal/compiler/implementation/source_file.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart';
@@ skipping 27 matching lines @@
 
   _PrivateClass get private => this;
 }
 ''';
 
 
 void analyze(String text, [expectedWarnings]) {
   if (expectedWarnings == null) expectedWarnings = [];
   if (expectedWarnings is !List) expectedWarnings = [expectedWarnings];
 
-  MockCompiler compiler = new MockCompiler(analyzeOnly: true);
+  MockCompiler compiler = new MockCompiler.internal(analyzeOnly: true);
   compiler.registerSource(Uri.parse(PRIVATE_SOURCE_URI), PRIVATE_SOURCE);
   compiler.diagnosticHandler = (uri, int begin, int end, String message, kind) {
     SourceFile sourceFile = compiler.sourceFiles[uri.toString()];
     if (sourceFile != null) {
       print(sourceFile.getLocationMessage(message, begin, end, true, (x) => x));
     } else {
       print(message);
     }
   };
 
@@ skipping 99 matching lines @@
   // Call public getter on public class.
   analyze('var value = publicClass.publicGetter;');
   // Call public setter on public class.
   analyze('publicClass.publicSetter = 0;');
   // Access public method on public class.
   analyze('var value = publicClass.publicMethod;');
   // Call public method on public class.
   analyze('publicClass.publicMethod();');
 }