Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/get/hosted/avoid_network_requests_test.dart

-// Copyright (c) 2012, 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 'package:scheduled_test/scheduled_test.dart';
-
-import '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-
-  integration('only requests versions that are needed during solving', () {
-    servePackages((builder) {
-      builder.serve("foo", "1.0.0");
-      builder.serve("foo", "1.1.0");
-      builder.serve("foo", "1.2.0");
-      builder.serve("bar", "1.0.0");
-      builder.serve("bar", "1.1.0");
-      builder.serve("bar", "1.2.0");
-    });
-
-    d.appDir({
-      "foo": "any"
-    }).create();
-
-    // Get once so it gets cached.
-    pubGet();
-
-    // Clear the cache. We don't care about anything that was served during
-    // the initial get.
-    getRequestedPaths();
-
-    // Add "bar" to the dependencies.
-    d.appDir({
-      "foo": "any",
-      "bar": "any"
-    }).create();
-
-    // Run the solver again.
-    pubGet();
-
-    d.packagesDir({
-      "foo": "1.2.0",
-      "bar": "1.2.0"
-    }).validate();
-
-    // The get should not have done any network requests since the lock file is
-    // up to date.
-    getRequestedPaths().then((paths) {
-      expect(
-          paths,
-          unorderedEquals([// Bar should be requested because it's new, but not foo.
-        "api/packages/bar", // Should only request the most recent version.
-        "api/packages/bar/versions/1.2.0", // Need to download it.
-        "packages/bar/versions/1.2.0.tar.gz"]));
-    });
-  });
-}