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

sdk/lib/_internal/pub_generated/test/dart2js/omits_source_map_if_sourceMaps_false_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 '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-main() {
-  initConfig();
-  integration("omits source maps from a debug build if sourceMaps false", () {
-    d.dir(appPath, [d.pubspec({
-        'name': 'myapp',
-        'transformers': [{
-            '\$dart2js': {
-              'sourceMaps': false
-            }
-          }]
-      }),
-          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.nothing('main.dart.js.map')])])]).validate();
-  });
-}