Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/global/binstubs/does_not_warn_if_on_path_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 'dart:io';
-
-import 'package:path/path.dart' as p;
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-  integration("does not warn if the binstub directory is on the path", () {
-    servePackages((builder) {
-      builder.serve("foo", "1.0.0", pubspec: {
-        "executables": {
-          "script": null
-        }
-      },
-          contents: [
-              d.dir("bin", [d.file("script.dart", "main(args) => print('ok \$args');")])]);
-    });
-
-    // Add the test's cache bin directory to the path.
-    var binDir = p.dirname(Platform.executable);
-    var separator = Platform.operatingSystem == "windows" ? ";" : ":";
-    var path = "${Platform.environment["PATH"]}$separator$binDir";
-
-    schedulePub(
-        args: ["global", "activate", "foo"],
-        output: isNot(contains("is not on your path")),
-        environment: {
-      "PATH": path
-    });
-  });
-}