Add offline support to pub install and update.

sdk/lib/_internal/pub/test/update/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 'dart:io';
+
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+
+main() {
+  initConfig();
+  integration('updates a package using the cache', () {
+    // Run the server so that we know what URL to use in the system cache.
+    servePackages([]);
+
+    d.cacheDir({
+      "foo": ["1.2.2", "1.2.3"],
+      "bar": ["1.2.3"]
+    }, includePubspecs: true).create();
+
+    d.appDir([
+      dependencyMap("foo", "any"),
+      dependencyMap("bar", "any")
+    ]).create();
+
+    schedulePub(args: ['update', '--offline'],
+        output: new RegExp("Dependencies updated!\$"),
+        error: "Warning: Updating when offline may not update you "
+               "to the latest versions of your dependencies.");
+
+    d.packagesDir({
+      "foo": "1.2.3",
+      "bar": "1.2.3"
+    }).validate();
+  });

[nweiz, 2013/05/06 23:02:25]

We should test failure cases here, too.

[Bob Nystrom, 2013/05/07 21:03:09]

Done.

+}