Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/serve/does_not_get_first_if_locked_matches_override_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.
-
-library pub_tests;
-
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-import 'utils.dart';
-
-main() {
-  // This is a regression test for https://dartbug.com/15180.
-  initConfig();
-  integration("does not get if the locked version matches the override", () {
-    d.dir("foo", [d.libPubspec("foo", "0.0.1"), d.libDir("foo")]).create();
-
-    // Get "foo" into the lock file.
-    d.dir(appPath, [d.pubspec({
-        "name": "myapp",
-        "dependencies": {
-          "foo": "any"
-        },
-        "dependency_overrides": {
-          "foo": {
-            "path": "../foo",
-            "version": ">=0.0.1"
-          }
-        }
-      })]).create();
-    pubGet();
-
-    pubServe(shouldGetFirst: false);
-    requestShouldSucceed("packages/foo/foo.dart", 'main() => "foo";');
-    endPubServe();
-  });
-}