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

sdk/lib/_internal/pub_generated/test/hosted/version_negotiation_test.dart

 // Copyright (c) 2012, 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.
 
 library pub_tests;
 
 import 'package:scheduled_test/scheduled_server.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 import 'package:shelf/shelf.dart' as shelf;
 
@@ skipping 12 matching lines @@
           "hosted": {
             "name": "foo",
             "url": server.url.then((url) => url.toString())
           }
         }
       }).create();
 
       var pub = startPub(args: [command.name]);
 
       server.handle('GET', '/api/packages/foo', (request) {
-        expect(request.headers['accept'],
+        expect(
+            request.headers['accept'],
             equals('application/vnd.pub.v2+json'));
         return new shelf.Response(200);
       });
 
       pub.kill();
     });
 
     integration('prints a friendly error if the version is out-of-date', () {
       var server = new ScheduledServer();
 
       d.appDir({
         "foo": {
           "hosted": {
             "name": "foo",
             "url": server.url.then((url) => url.toString())
           }
         }
       }).create();
 
       var pub = startPub(args: [command.name]);
 
-      server.handle('GET', '/api/packages/foo',
+      server.handle(
+          'GET',
+          '/api/packages/foo',
           (request) => new shelf.Response(406));
 
       pub.shouldExit(1);
 
-      pub.stderr.expect(emitsLines(
-          "Pub 0.1.2+3 is incompatible with the current version of localhost.\n"
-          "Upgrade pub to the latest version and try again."));
+      pub.stderr.expect(
+          emitsLines(
+              "Pub 0.1.2+3 is incompatible with the current version of localhost.\n"
+                  "Upgrade pub to the latest version and try again."));
     });
   });
 }