Add an HTTP library that wraps dart:io.

pkg/http/test/streamed_request_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 streamed_request_test;
+
+import 'dart:io';
+
+import '../../unittest/lib/unittest.dart';
+import '../lib/http.dart' as http;
+import 'utils.dart';
+
+void main() {
+  test('#finalize freezes contentLength', () {
+    var request = new http.StreamedRequest('POST', dummyUrl);
+    request.finalize();
+
+    expect(request.contentLength, equals(-1));
+    expect(() => request.contentLength = 10, throwsStateError);
+  });
+}