Make dart2js unittests async.

tests/compiler/dart2js/pretty_parameter_test.dart

 // Copyright (c) 2011, 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 that parameters keep their names in the output.
 
-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 FOO = r"""
 void foo(var a, var b) {
 }
 """;
 
 const String BAR = r"""
 void bar(var eval, var $eval) {
 }
@@ skipping 47 matching lines @@
   var result = start;
   if (test) {
     foo(1, 2);
     result = 42;
   }
   print(result);
 }
 """;
 
 main() {
-  String generated = compile(FOO, entry: 'foo');
-  Expect.isTrue(generated.contains(r"function(a, b) {"));
+  asyncTest(() => Future.wait([
+    compile(FOO, entry: 'foo', check: (String generated) {
+      Expect.isTrue(generated.contains(r"function(a, b) {"));
+    }),
 
-  generated = compile(BAR, entry: 'bar');
-  Expect.isTrue(generated.contains(r"function($eval, $$eval) {"));
+    compile(BAR, entry: 'bar', check: (String generated) {
+      Expect.isTrue(generated.contains(r"function($eval, $$eval) {"));
+    }),
 
-  generated = compile(PARAMETER_AND_TEMP, entry: 'bar');
-  Expect.isTrue(generated.contains(r"print(t00)"));
-  // Check that the second 't0' got another name.
-  Expect.isTrue(generated.contains(r"print(t01)"));
+    compile(PARAMETER_AND_TEMP, entry: 'bar', check: (String generated) {
+      Expect.isTrue(generated.contains(r"print(t00)"));
+      // Check that the second 't0' got another name.
+      Expect.isTrue(generated.contains(r"print(t01)"));
+    }),
 
-  generated = compile(MULTIPLE_PHIS_ONE_LOCAL, entry: 'foo');
-  Expect.isTrue(generated.contains("var a;"));
-  // Check that there is only one var declaration.
-  checkNumberOfMatches(new RegExp("var").allMatches(generated).iterator, 1);
+    compile(MULTIPLE_PHIS_ONE_LOCAL, entry: 'foo', check: (String generated) {
+      Expect.isTrue(generated.contains("var a;"));
+      // Check that there is only one var declaration.
+      checkNumberOfMatches(new RegExp("var").allMatches(generated).iterator, 1);
+    }),
 
-  generated = compile(NO_LOCAL, entry: 'foo');
-  Expect.isFalse(generated.contains('var'));
+    compile(NO_LOCAL, entry: 'foo', check: (String generated) {
+      Expect.isFalse(generated.contains('var'));
+    }),
 
-  generated = compile(PARAMETER_INIT, entry: 'foo');
-  // Check that there is only one var declaration.
-  checkNumberOfMatches(new RegExp("var").allMatches(generated).iterator, 1);
+    compile(PARAMETER_INIT, entry: 'foo', check: (String generated) {
+      // Check that there is only one var declaration.
+      checkNumberOfMatches(new RegExp("var").allMatches(generated).iterator, 1);
+    }),
+  ]));
 }