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

sdk/lib/_internal/pub_generated/test/run/runs_a_generated_script_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';
 
 const TRANSFORMER = """
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 
 class DartTransformer extends Transformer {
   DartTransformer.asPlugin();
 
   String get allowedExtensions => '.in';
 
   void apply(Transform transform) {
     transform.addOutput(new Asset.fromString(
         new AssetId("myapp", "bin/script.dart"),
         "void main() => print('generated');"));
   }
 }
 """;
 
 main() {
   initConfig();
   withBarbackVersions("any", () {
     integration('runs a script generated from scratch by a transformer', () {
-      d.dir(appPath, [
-        d.pubspec({
+      d.dir(appPath, [d.pubspec({
           "name": "myapp",
           "transformers": ["myapp/src/transformer"]
         }),
-        d.dir("lib", [d.dir("src", [
-          d.file("transformer.dart", TRANSFORMER),
-          d.file("primary.in", "")
-        ])])
-      ]).create();
+            d.dir(
+                "lib",
+                [
+                    d.dir(
+                        "src",
+                        [
+                            d.file("transformer.dart", TRANSFORMER),
+                            d.file("primary.in", "")])])]).create();
 
       createLockFile('myapp', pkg: ['barback']);
 
       var pub = pubRun(args: ["script"]);
 
       pub.stdout.expect("generated");
       pub.shouldExit();
     });
   });
 }