Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/cache/add/all_with_some_versions_present_test.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.
-
-library pub_tests;
-
-import '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-  integration('"--all" adds all non-installed versions of the package', () {
-    servePackages((builder) {
-      builder.serve("foo", "1.2.1");
-      builder.serve("foo", "1.2.2");
-      builder.serve("foo", "1.2.3");
-      builder.serve("foo", "2.0.0");
-    });
-
-    // Install a couple of versions first.
-    schedulePub(
-        args: ["cache", "add", "foo", "-v", "1.2.1"],
-        output: 'Downloading foo 1.2.1...');
-
-    schedulePub(
-        args: ["cache", "add", "foo", "-v", "1.2.3"],
-        output: 'Downloading foo 1.2.3...');
-
-    // They should show up as already installed now.
-    schedulePub(args: ["cache", "add", "foo", "--all"], output: '''
-          Already cached foo 1.2.1.
-          Downloading foo 1.2.2...
-          Already cached foo 1.2.3.
-          Downloading foo 2.0.0...''');
-
-    d.cacheDir({
-      "foo": "1.2.1"
-    }).validate();
-    d.cacheDir({
-      "foo": "1.2.2"
-    }).validate();
-    d.cacheDir({
-      "foo": "1.2.3"
-    }).validate();
-    d.cacheDir({
-      "foo": "2.0.0"
-    }).validate();
-  });
-}