Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/build/utils.dart

Index: sdk/lib/_internal/pub_generated/test/build/utils.dart
diff --git a/sdk/lib/_internal/pub_generated/test/build/utils.dart b/sdk/lib/_internal/pub_generated/test/build/utils.dart
deleted file mode 100644
index 6160c5eefe2fbc00d9f2678aad44fc45eb156408..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/test/build/utils.dart
+++ /dev/null
@@ -1,45 +0,0 @@
-// Copyright (c) 2013, 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:convert';
-
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-/// Runs the hosted test server and serves a valid "browser" package that
-/// contains the same files (but not their contents) as the real browser
-/// package.
-void serveBrowserPackage() {
-  serve([d.dir('api', [d.dir('packages', [d.file('browser', JSON.encode({
-          'versions': [packageVersionApiMap(packageMap('browser', '1.0.0'))]
-        })),
-            d.dir(
-                'browser',
-                [
-                    d.dir(
-                        'versions',
-                        [
-                            d.file(
-                                '1.0.0',
-                                JSON.encode(
-                                    packageVersionApiMap(packageMap('browser', '1.0.0'), full: true)))])])])]),
-            d.dir(
-                'packages',
-                [
-                    d.dir(
-                        'browser',
-                        [
-                            d.dir(
-                                'versions',
-                                [
-                                    d.tar(
-                                        '1.0.0.tar.gz',
-                                        [
-                                            d.file('pubspec.yaml', yaml(packageMap("browser", "1.0.0"))),
-                                            d.dir(
-                                                'lib',
-                                                [
-                                                    d.file('dart.js', 'contents of dart.js'),
-                                                    d.file('interop.js', 'contents of interop.js')])])])])])]);
-}