First pass at asynchronous input loading in dart2js.

tests/compiler/dart2js/no_duplicate_constructor_body_test.dart

Index: tests/compiler/dart2js/no_duplicate_constructor_body_test.dart
diff --git a/tests/compiler/dart2js/no_duplicate_constructor_body_test.dart b/tests/compiler/dart2js/no_duplicate_constructor_body_test.dart
index 3942536ef672f86efecc7671f9fcf3620e084403..8f46e3cdbd3698bfd121a1d8de78ed5530d1571e 100644
--- a/tests/compiler/dart2js/no_duplicate_constructor_body_test.dart
+++ b/tests/compiler/dart2js/no_duplicate_constructor_body_test.dart
@@ -2,6 +2,7 @@
 // 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 "../../async_helper.dart";
 import 'compiler_helper.dart';
 
 const String CODE = """
@@ -15,8 +16,9 @@ main() {
 """;
 
 main() {
-  String generated = compileAll(CODE);
-  RegExp regexp = new RegExp(r'\A: {"": "[A-za-z]+;"');
-  Iterator<Match> matches = regexp.allMatches(generated).iterator;
-  checkNumberOfMatches(matches, 1);
+  asyncTest(() => compileAll(CODE).then((generated) {
+    RegExp regexp = new RegExp(r'\A: {"": "[A-za-z]+;"');
+    Iterator<Match> matches = regexp.allMatches(generated).iterator;
+    checkNumberOfMatches(matches, 1);
+  }));
 }