Add a multipart HTTP request class.

pkg/http/lib/http.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.
 
 /// 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;
@@ skipping 48 matching lines @@
 import 'dart:scalarlist';
 import 'dart:uri';
 
 import 'src/client.dart';
 import 'src/response.dart';
 
 export 'src/base_client.dart';
 export 'src/base_request.dart';
 export 'src/base_response.dart';
 export 'src/client.dart';
+export 'src/multipart_file.dart';
+export 'src/multipart_request.dart';
 export 'src/request.dart';
 export 'src/response.dart';
 export 'src/streamed_request.dart';
 export 'src/streamed_response.dart';
 
 /// Sends an HTTP HEAD request with the given headers to the given URL, which
 /// can be a [Uri] or a [String].
 ///
 /// This automatically initializes a new [Client] and closes that client once
 /// the request is complete. If you're planning on making multiple requests to
@@ skipping 86 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.onComplete((_) => client.close());
   return future;
 }