Migrate missed file.

tests/language/async_backwards_compatibility_1_test.dart

Index: tests/language/async_backwards_compatibility_1_test.dart
diff --git a/tests/language/async_backwards_compatibility_1_test.dart b/tests/language/async_backwards_compatibility_1_test.dart
deleted file mode 100644
index 93908797af9400f0cdc751626158e1f4e39f6af5..0000000000000000000000000000000000000000
--- a/tests/language/async_backwards_compatibility_1_test.dart
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright (c) 2014, 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 'async_helper_lib.dart' as async;
-
-class A {
-  async.async get async => null;
-}
-
-async.async topLevel() => null;
-
-main() {
-  var a = new A();
-  var b = a.async;
-  var c = topLevel();
-}