Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/global/activate/removes_old_lockfile_test.dart

-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS 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('removes the 1.6-style lockfile', () {
-    servePackages((builder) {
-      builder.serve("foo", "1.0.0");
-    });
-
-    d.dir(
-        cachePath,
-        [
-            d.dir(
-                'global_packages',
-                [
-                    d.file(
-                        'foo.lock',
-                        'packages: {foo: {description: foo, source: hosted, '
-                            'version: "1.0.0"}}}')])]).create();
-
-    schedulePub(args: ["global", "activate", "foo"]);
-
-    d.dir(
-        cachePath,
-        [
-            d.dir(
-                'global_packages',
-                [
-                    d.nothing('foo.lock'),
-                    d.dir('foo', [d.matcherFile('pubspec.lock', contains('1.0.0'))])])]).validate();
-  });
-}