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

sdk/lib/_internal/pub_generated/test/transformer/exclusion/exclude_asset_prefix_test.dart

 // Copyright (c) 2014, 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 '../../serve/utils.dart';
 
 main() {
   initConfig();
   withBarbackVersions("any", () {
     integration("allows a directory prefix to exclude", () {
-      d.dir(appPath, [
-        d.pubspec({
+      d.dir(appPath, [d.pubspec({
           "name": "myapp",
-          "transformers": [
-            {
+          "transformers": [{
               "myapp/src/transformer": {
                 "\$exclude": "web/sub"
               }
-            }
-          ]
+            }]
         }),
-        d.dir("lib", [d.dir("src", [
-          d.file("transformer.dart", REWRITE_TRANSFORMER)
-        ])]),
-        d.dir("web", [
-          d.file("foo.txt", "foo"),
-          d.file("bar.txt", "bar"),
-          d.dir("sub", [
-            d.file("foo.txt", "foo"),
-          ]),
-          d.dir("subbub", [
-            d.file("foo.txt", "foo"),
-          ])
-        ])
-      ]).create();
+            d.dir("lib", [d.dir("src", [d.file("transformer.dart", REWRITE_TRANSFORMER)])]),
+            d.dir(
+                "web",
+                [
+                    d.file("foo.txt", "foo"),
+                    d.file("bar.txt", "bar"),
+                    d.dir("sub", [d.file("foo.txt", "foo"),]),
+                    d.dir("subbub", [d.file("foo.txt", "foo"),])])]).create();
 
       createLockFile('myapp', pkg: ['barback']);
 
       pubServe();
       requestShouldSucceed("foo.out", "foo.out");
       requestShouldSucceed("bar.out", "bar.out");
       requestShouldSucceed("subbub/foo.out", "foo.out");
       requestShould404("sub/foo.out");
       endPubServe();
     });
   });
 }