Regenerate pub using the latest version of async-await.

sdk/lib/_internal/pub_generated/test/global/binstubs/utils.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 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
 
 import '../../test_pub.dart';
 
 /// The buildbots do not have the Dart SDK (containing "dart" and "pub") on
 /// their PATH, so we need to spawn the binstub process with a PATH that
 /// explicitly includes it.
 Future<Map> getEnvironment() {
   final completer0 = new Completer();
   scheduleMicrotask(() {
     try {
       var binDir = p.dirname(Platform.executable);
       join0(x0) {
         var separator = x0;
         var path = "${Platform.environment["PATH"]}${separator}${binDir}";
-        getPubTestEnvironment().then((x1) {
+        new Future.value(getPubTestEnvironment()).then((x1) {
           try {
             var environment = x1;
             environment["PATH"] = path;
             completer0.complete(environment);
           } catch (e0, s0) {
             completer0.completeError(e0, s0);
           }
         }, onError: completer0.completeError);
       }
       if (Platform.operatingSystem == "windows") {
         join0(";");
       } else {
         join0(":");
       }
     } catch (e, s) {
       completer0.completeError(e, s);
     }
   });
   return completer0.future;
 }