Add a shortcut for PATCH.

lib/http.dart

 // 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.
 library http;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';
@@ skipping 78 matching lines @@
 ///
 /// [encoding] defaults to [UTF8].
 ///
 /// For more fine-grained control over the request, use [Request] or
 /// [StreamedRequest] instead.
 Future<Response> put(url, {Map<String, String> headers, body,
     Encoding encoding}) =>
   _withClient((client) => client.put(url,
       headers: headers, body: body, encoding: encoding));
 
+/// Sends an HTTP PATCH request with the given headers and body to the given
+/// URL, which can be a [Uri] or a [String].
+///
+/// [body] sets the body of the request. It can be a [String], a [List<int>] or
+/// a [Map<String, String>]. If it's a String, it's encoded using [encoding] and
+/// used as the body of the request. The content-type of the request will
+/// default to "text/plain".
+///
+/// If [body] is a List, it's used as a list of bytes for the body of the
+/// request.
+///
+/// If [body] is a Map, it's encoded as form fields using [encoding]. The
+/// content-type of the request will be set to
+/// `"application/x-www-form-urlencoded"`; this cannot be overridden.
+///
+/// [encoding] defaults to [UTF8].
+///
+/// For more fine-grained control over the request, use [Request] or
+/// [StreamedRequest] instead.
+Future<Response> patch(url, {Map<String, String> headers, body,
+    Encoding encoding}) =>
+  _withClient((client) => client.patch(url,
+      headers: headers, body: body, encoding: encoding));
+
 /// Sends an HTTP DELETE 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
 /// the same server, you should use a single [Client] for all of those requests.
 ///
 /// For more fine-grained control over the request, use [Request] instead.
 Future<Response> delete(url, {Map<String, String> headers}) =>
   _withClient((client) => client.delete(url, headers: headers));
@@ skipping 28 matching lines @@
 /// For more fine-grained control over the request and response, use [Request]
 /// 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);
   return future.whenComplete(client.close);
 }