Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/run/runs_named_app_in_dev_dependency_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 '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-main() {
-  initConfig();
-  integration('runs a named Dart application in a dev dependency', () {
-    d.dir(
-        "foo",
-        [
-            d.libPubspec("foo", "1.0.0"),
-            d.dir("bin", [d.file("bar.dart", "main() => print('foobar');")])]).create();
-
-    d.dir(appPath, [d.pubspec({
-        "name": "myapp",
-        "dev_dependencies": {
-          "foo": {
-            "path": "../foo"
-          }
-        }
-      })]).create();
-
-    pubGet();
-
-    var pub = pubRun(args: ["foo:bar"]);
-    pub.stdout.expect("foobar");
-    pub.shouldExit();
-  });
-}