Revert "Use native async/await support in pub."

sdk/lib/_internal/pub_generated/test/serve/watch_modified_file_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() {
   initConfig();
   integration("watches modifications to files", () {
-    d.dir(appPath, [
-      d.appPubspec(),
-      d.dir("web", [
-        d.file("index.html", "before")
-      ])
-    ]).create();
+    d.dir(
+        appPath,
+        [d.appPubspec(), d.dir("web", [d.file("index.html", "before")])]).create();
 
     pubServe();
     requestShouldSucceed("index.html", "before");
 
-    d.dir(appPath, [
-      d.dir("web", [
-        d.file("index.html", "after")
-      ])
-    ]).create();
+    d.dir(appPath, [d.dir("web", [d.file("index.html", "after")])]).create();
 
     waitForBuildSuccess();
     requestShouldSucceed("index.html", "after");
     endPubServe();
   });
 }