Make dart2js unittests async.

tests/compiler/dart2js/constant_folding_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.
 // Test constant folding on numbers.
 
-import "package:expect/expect.dart";
+import 'dart:async';
+import 'package:expect/expect.dart';
+import 'package:async_helper/async_helper.dart';
 import 'compiler_helper.dart';
 
 const String NUMBER_FOLDING = """
 void main() {
   var a = 4;
   var b = 3;
   print(a + b);
 }
 """;
 
@@ skipping 32 matching lines @@
 }
 """;
 
 const String RANGE_ERROR_INDEX_FOLDING = """
 foo() {
   return [1][1];
 }
 """;
 
 main() {
-  compileAndMatch(
-      NUMBER_FOLDING, 'main', new RegExp(r"print\(7\)"));
-  compileAndMatch(
-      NEGATIVE_NUMBER_FOLDING, 'main', new RegExp(r"print\(1\)"));
+  asyncTest(() => Future.wait([
+    compileAndMatch(
+        NUMBER_FOLDING, 'main', new RegExp(r"print\(7\)")),
+    compileAndMatch(
+        NEGATIVE_NUMBER_FOLDING, 'main', new RegExp(r"print\(1\)")),
 
-  String generated = compile(NULL_EQUALS_FOLDING, entry: 'foo');
-  RegExp regexp = new RegExp(r'a == null');
-  Expect.isTrue(regexp.hasMatch(generated));
+    compile(NULL_EQUALS_FOLDING, entry: 'foo', check: (String generated) {
+      RegExp regexp = new RegExp(r'a == null');
+      Expect.isTrue(regexp.hasMatch(generated));
 
-  regexp = new RegExp(r'null == b');
-  Expect.isTrue(regexp.hasMatch(generated));
+      regexp = new RegExp(r'null == b');
+      Expect.isTrue(regexp.hasMatch(generated));
 
-  regexp = new RegExp(r'4 === c');
-  Expect.isTrue(regexp.hasMatch(generated));
+      regexp = new RegExp(r'4 === c');
+      Expect.isTrue(regexp.hasMatch(generated));
 
-  regexp = new RegExp('"foo" === d');
-  Expect.isTrue(regexp.hasMatch(generated));
+      regexp = new RegExp('"foo" === d');
+      Expect.isTrue(regexp.hasMatch(generated));
+    }),
 
-  compileAndMatch(
-      LIST_LENGTH_FOLDING, 'foo', new RegExp(r"return 3"));
+    compileAndMatch(
+        LIST_LENGTH_FOLDING, 'foo', new RegExp(r"return 3")),
 
-  compileAndMatch(
-      LIST_INDEX_FOLDING, 'foo', new RegExp(r"return 1"));
+    compileAndMatch(
+        LIST_INDEX_FOLDING, 'foo', new RegExp(r"return 1")),
 
-  compileAndDoNotMatch(
-      LIST_INDEX_FOLDING, 'foo', new RegExp(r"ioore"));
+    compileAndDoNotMatch(
+        LIST_INDEX_FOLDING, 'foo', new RegExp(r"ioore")),
 
-  compileAndMatch(
-      STRING_LENGTH_FOLDING, 'foo', new RegExp(r"return 3"));
+    compileAndMatch(
+        STRING_LENGTH_FOLDING, 'foo', new RegExp(r"return 3")),
 
-  compileAndMatch(
-      RANGE_ERROR_INDEX_FOLDING, 'foo', new RegExp(r"ioore"));
+    compileAndMatch(
+        RANGE_ERROR_INDEX_FOLDING, 'foo', new RegExp(r"ioore")),
+  ]));
 }