Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/dart2js/unminified_in_nonrelease_mode_test.dart

Index: sdk/lib/_internal/pub_generated/test/dart2js/unminified_in_nonrelease_mode_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/dart2js/unminified_in_nonrelease_mode_test.dart b/sdk/lib/_internal/pub_generated/test/dart2js/unminified_in_nonrelease_mode_test.dart
deleted file mode 100644
index e31219306a73ed9bef70aa63e284f79c4c05c1bd..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/test/dart2js/unminified_in_nonrelease_mode_test.dart
+++ /dev/null
@@ -1,24 +0,0 @@
-// Copyright (c) 2013, 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.
-
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-import '../serve/utils.dart';
-
-main() {
-  initConfig();
-  integration("generates unminified JS when not in release mode", () {
-    d.dir(
-        appPath,
-        [
-            d.appPubspec(),
-            d.dir(
-                "web",
-                [d.file("main.dart", "void main() => print('hello');")])]).create();
-
-    pubServe(args: ["--mode", "whatever"]);
-    requestShouldSucceed("main.dart.js", isUnminifiedDart2JSOutput);
-    endPubServe();
-  });
-}