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

sdk/lib/_internal/pub_generated/test/global/run/mode_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 {
   final BarbackSettings _settings;
 
   DartTransformer.asPlugin(this._settings);
 
   String get allowedExtensions => '.in';
 
   void apply(Transform transform) {
     transform.addOutput(new Asset.fromString(
         new AssetId(transform.primaryInput.id.package, "bin/script.dart"),
         "void main() => print('\${_settings.mode.name}');"));
   }
 }
 """;
 
 main() {
   initConfig();
-  integration('runs a script in an activated package with customizable modes',
+  integration(
+      'runs a script in an activated package with customizable modes',
       () {
     servePackages((builder) {
       builder.serveRepoPackage("barback");
 
-      builder.serve("foo", "1.0.0",
-          deps: {"barback": "any"},
-          pubspec: {"transformers": ["foo/src/transformer"]},
+      builder.serve("foo", "1.0.0", deps: {
+        "barback": "any"
+      }, pubspec: {
+        "transformers": ["foo/src/transformer"]
+      },
           contents: [
-        d.dir("lib", [d.dir("src", [
-          d.file("transformer.dart", TRANSFORMER),
-          d.file("primary.in", "")
-        ])])
-      ]);
+              d.dir(
+                  "lib",
+                  [
+                      d.dir(
+                          "src",
+                          [d.file("transformer.dart", TRANSFORMER), d.file("primary.in", "")])])]);
     });
 
     schedulePub(args: ["global", "activate", "foo"]);
 
     // By default it should run in release mode.
     var pub = pubRun(global: true, args: ["foo:script"]);
     pub.stdout.expect("release");
     pub.shouldExit();
 
     // A custom mode should be specifiable.
     pub = pubRun(global: true, args: ["--mode", "custom-mode", "foo:script"]);
     pub.stdout.expect("custom-mode");
     pub.shouldExit();
   });
 }