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

sdk/lib/_internal/pub_generated/test/dart2js/includes_source_maps_in_debug_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.
-
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-main() {
-  initConfig();
-  integration("includes source map URLs in a debug build", () {
-    d.dir(
-        appPath,
-        [
-            d.appPubspec(),
-            d.dir(
-                "web",
-                [d.file("main.dart", "void main() => print('hello');")])]).create();
-
-    schedulePub(
-        args: ["build", "--mode", "debug"],
-        output: new RegExp(r'Built \d+ files to "build".'),
-        exitCode: 0);
-
-    d.dir(
-        appPath,
-        [
-            d.dir(
-                'build',
-                [
-                    d.dir(
-                        'web',
-                        [
-                            d.matcherFile('main.dart.js', contains("# sourceMappingURL=main.dart.js.map")),
-                            d.matcherFile(
-                                'main.dart.js.map',
-                                contains('"file": "main.dart.js"'))])])]).validate();
-  });
-}