Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/get/git/lock_version_test.dart

-// Copyright (c) 2012, 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.
-
-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';
-
-main() {
-  initConfig();
-  integration('keeps a Git package locked to the version in the lockfile', () {
-    ensureGit();
-
-    d.git('foo.git', [d.libDir('foo'), d.libPubspec('foo', '1.0.0')]).create();
-
-    d.appDir({
-      "foo": {
-        "git": "../foo.git"
-      }
-    }).create();
-
-    // This get should lock the foo.git dependency to the current revision.
-    pubGet();
-
-    d.dir(
-        packagesPath,
-        [d.dir('foo', [d.file('foo.dart', 'main() => "foo";')])]).validate();
-
-    // Delete the packages path to simulate a new checkout of the application.
-    schedule(() => deleteEntry(path.join(sandboxDir, packagesPath)));
-
-    d.git(
-        'foo.git',
-        [d.libDir('foo', 'foo 2'), d.libPubspec('foo', '1.0.0')]).commit();
-
-    // This get shouldn't upgrade the foo.git dependency due to the lockfile.
-    pubGet();
-
-    d.dir(
-        packagesPath,
-        [d.dir('foo', [d.file('foo.dart', 'main() => "foo";')])]).validate();
-  });
-}