Store the async-await compiled pub code directly in the repo.

sdk/lib/_internal/pub_generated/test/serve/missing_asset_test.dart

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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.
-
 library pub_tests;
-
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import 'utils.dart';
-
 main() {
   initConfig();
   integration("responds with a 404 for missing assets", () {
-    d.dir(appPath, [
-      d.appPubspec()
-    ]).create();
-
+    d.dir(appPath, [d.appPubspec()]).create();
     pubServe();
     requestShould404("index.html");
     requestShould404("packages/myapp/nope.dart");
     requestShould404("dir/packages/myapp/nope.dart");
     endPubServe();
   });
 }