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

sdk/lib/_internal/pub_generated/test/serve/gets_first_if_dependency_is_not_installed_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 'package:path/path.dart' as path;
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../../lib/src/io.dart';
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-import 'utils.dart';
-
-main() {
-  initConfig();
-  integration("gets first if a dependency is not installed", () {
-    servePackages((builder) => builder.serve("foo", "1.2.3"));
-
-    d.appDir({
-      "foo": "1.2.3"
-    }).create();
-
-    // Run pub to get a lock file.
-    pubGet();
-
-    // Delete the system cache so it isn't installed any more.
-    schedule(() => deleteEntry(path.join(sandboxDir, cachePath)));
-
-    pubServe(shouldGetFirst: true);
-    requestShouldSucceed("packages/foo/foo.dart", 'main() => "foo 1.2.3";');
-    endPubServe();
-  });
-}