Revert "Revert "Use native async/await support in pub.""

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

-// Copyright (c) 2014, 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("serves a filename with a space", () {
-    d.dir(
-        appPath,
-        [
-            d.appPubspec(),
-            d.dir(
-                "web",
-                [
-                    d.file("foo bar.txt", "outer contents"),
-                    d.dir("sub dir", [d.file("inner.txt", "inner contents"),])])]).create();
-
-    pubServe();
-    requestShouldSucceed("foo%20bar.txt", "outer contents");
-    requestShouldSucceed("sub%20dir/inner.txt", "inner contents");
-    endPubServe();
-  });
-}