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

sdk/lib/_internal/pub_generated/test/global/binstubs/utils.dart

Index: sdk/lib/_internal/pub_generated/test/global/binstubs/utils.dart
diff --git a/sdk/lib/_internal/pub_generated/test/global/binstubs/utils.dart b/sdk/lib/_internal/pub_generated/test/global/binstubs/utils.dart
new file mode 100644
index 0000000000000000000000000000000000000000..bd2243f4a8c22f5259e328451f4b346094316f5b
--- /dev/null
+++ b/sdk/lib/_internal/pub_generated/test/global/binstubs/utils.dart
@@ -0,0 +1,43 @@
+// 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}";
+        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;
+}