Update tests for pkg/http for new library

pkg/http/lib/http.dart

-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
 /// A composable, [Future]-based library for making HTTP requests.
 ///
 /// The easiest way to use this library is via the top-level functions. They
 /// allow you to make individual HTTP requests with minimal hassle:
 ///
 ///     import 'package:http/http.dart' as http;
 ///
 ///     var url = "http://example.com/whatsit/create";
 ///     http.post(url, fields: {"name": "doodle", "color": "blue"})
 ///         .then((response) {
 ///       print("Response status: ${response.statusCode}");
 ///       print("Response body: ${response.body}");
 ///     });
 ///
 ///     http.read("http://example.com/foobar.txt").then(print);
 ///
 /// If you're making multiple requests to the same server, you can keep open a
 /// persistent connection by using a [Client] rather than making one-off
 /// requests. If you do this, make sure to close the client when you're done:
 ///
 ///     var client = new http.Client();
 ///     client.post(
 ///         "http://example.com/whatsit/create",
 ///         fields: {"name": "doodle", "color": "blue"})
-///       .chain((response) => client.get(response.bodyFields['uri']))
+///       .then((response) => client.get(response.bodyFields['uri']))
 ///       .then((response) => print(response.body))
 ///       .onComplete((_) => client.close());
 ///
 /// You can also exert more fine-grained control over your requests and
 /// responses by creating [Request] or [StreamedRequest] objects yourself and
 /// passing them to [Client.send].
 ///
 /// This package is designed to be composable. This makes it easy for external
 /// libraries to work with one another to add behavior to it. Libraries wishing
 /// to add behavior should create a subclass of [BaseClient] that wraps another
@@ skipping 125 matching lines @@
 /// instead.
 Future<Uint8List> readBytes(url, {Map<String, String> headers}) =>
   _withClient((client) => client.readBytes(url, headers: headers));
 
 Future _withClient(Future fn(Client)) {
   var client = new Client();
   var future = fn(client);
   future.catchError((_) {}).then((_) => client.close());
   return future;
 }