Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/serve/web_socket/url_to_asset_id_with_line_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("provides output line number if given source one", () {
-    d.dir(
-        appPath,
-        [d.appPubspec(), d.dir("web", [d.file("main.dart", "main")])]).create();
-
-    pubServe();
-
-    // Paths in web/.
-    expectWebSocketResult("urlToAssetId", {
-      "url": getServerUrl("web", "main.dart"),
-      "line": 12345
-    }, {
-      "package": "myapp",
-      "path": "web/main.dart",
-      "line": 12345
-    });
-
-    endPubServe();
-  });
-}