Remove the http package from the repo.

pkg/http/lib/testing.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.
-
-/// This library contains testing classes for the HTTP library.
-///
-/// The [MockClient] class is a drop-in replacement for `http.Client` that
-/// allows test code to set up a local request handler in order to fake a server
-/// that responds to HTTP requests:
-///
-///     import 'dart:convert';
-///     import 'package:http/testing.dart';
-///
-///     var client = new MockClient((request) {
-///       if (request.url.path != "/data.json") {
-///         return new Response("", 404);
-///       }
-///       return new Response(JSON.encode({
-///         'numbers': [1, 4, 15, 19, 214]
-///       }, 200, headers: {
-///         'content-type': 'application/json'
-///       });
-///     };
-library http.testing;
-
-export 'src/mock_client.dart';