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

sdk/lib/_internal/pub_generated/test/hosted/offline_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 '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-main() {
-  initConfig();
-
-  forBothPubGetAndUpgrade((command) {
-    integration('upgrades a package using the cache', () {
-      // Run the server so that we know what URL to use in the system cache.
-      serveNoPackages();
-
-      d.cacheDir({
-        "foo": ["1.2.2", "1.2.3"],
-        "bar": ["1.2.3"]
-      }, includePubspecs: true).create();
-
-      d.appDir({
-        "foo": "any",
-        "bar": "any"
-      }).create();
-
-      var warning = null;
-      if (command == RunCommand.upgrade) {
-        warning =
-            "Warning: Upgrading when offline may not update you "
-                "to the latest versions of your dependencies.";
-      }
-
-      pubCommand(command, args: ['--offline'], warning: warning);
-
-      d.packagesDir({
-        "foo": "1.2.3",
-        "bar": "1.2.3"
-      }).validate();
-    });
-
-    integration('fails gracefully if a dependency is not cached', () {
-      // Run the server so that we know what URL to use in the system cache.
-      serveNoPackages();
-
-      d.appDir({
-        "foo": "any"
-      }).create();
-
-      pubCommand(
-          command,
-          args: ['--offline'],
-          error: "Could not find package foo in cache.");
-    });
-
-    integration('fails gracefully no cached versions match', () {
-      // Run the server so that we know what URL to use in the system cache.
-      serveNoPackages();
-
-      d.cacheDir({
-        "foo": ["1.2.2", "1.2.3"]
-      }, includePubspecs: true).create();
-
-      d.appDir({
-        "foo": ">2.0.0"
-      }).create();
-
-      pubCommand(
-          command,
-          args: ['--offline'],
-          error: "Package foo has no versions that match >2.0.0 derived from:\n"
-              "- myapp 0.0.0 depends on version >2.0.0");
-    });
-  });
-}