Make dart2js unittests async.

tests/compiler/dart2js/patch_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/dart2jslib.dart";
 import "../../../sdk/lib/_internal/compiler/implementation/elements/elements.dart";
 import "../../../sdk/lib/_internal/compiler/implementation/tree/tree.dart";
 import "../../../sdk/lib/_internal/compiler/implementation/util/util.dart";
 import "mock_compiler.dart";
 import "parser_helper.dart";
 
 Future<Compiler> applyPatch(String script, String patch,
                             {bool analyzeAll: false, bool analyzeOnly: false}) {
   String core = "$DEFAULT_CORELIB\n$script";
-  MockCompiler compiler = new MockCompiler(coreSource: core,
-                                           analyzeAll: analyzeAll,
-                                           analyzeOnly: analyzeOnly);
+  MockCompiler compiler = new MockCompiler.internal(coreSource: core,
+                                                    analyzeAll: analyzeAll,
+                                                    analyzeOnly: analyzeOnly);
   var uri = Uri.parse("core.dartp");
   compiler.sourceFiles[uri.toString()] = new MockFile(patch);
   var handler = new LibraryDependencyHandler(compiler);
   return compiler.patchParser.patchLibrary(handler, uri, compiler.coreLibrary)
       .then((_) {
     handler.computeExports();
     return compiler;
   });
 }
 
@@ skipping 854 matching lines @@
   testPatchNoGetter();
   testPatchNonSetter();
   testPatchNoSetter();
   testPatchNonFunction();
 
   testPatchAndSelector();
 
   testAnalyzeAllInjectedMembers();
   testTypecheckPatchedMembers();
 }