Add an IO implementation of WebSocketChannel.

lib/src/channel.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:async';
 
 import 'package:async/async.dart';
 import 'package:crypto/crypto.dart';
 import 'package:stream_channel/stream_channel.dart';
 
@@ skipping 52 matching lines @@
 
   Stream get stream => new StreamView(_webSocket);
 
   /// The sink for sending values to the other endpoint.
   ///
   /// This supports additional arguments to [WebSocketSink.close] that provide
   /// the remote endpoint reasons for closing the connection.
   WebSocketSink get sink => new WebSocketSink._(_webSocket);
 
   /// Signs a `Sec-WebSocket-Key` header sent by a WebSocket client as part of
-  /// the [initial handshake].
+  /// the [initial handshake][].
   ///
   /// The return value should be sent back to the client in a
   /// `Sec-WebSocket-Accept` header.
   ///
   /// [initial handshake]: https://tools.ietf.org/html/rfc6455#section-4.2.2
   static String signKey(String key) {
     var hash = new SHA1();
     // We use [codeUnits] here rather than UTF-8-decoding the string because
     // [key] is expected to be base64 encoded, and so will be pure ASCII.
     hash.add((key + webSocketGUID).codeUnits);
@@ skipping 34 matching lines @@
   ///
   /// [closeCode] and [closeReason] are the [close code][] and [reason][] sent
   /// to the remote peer, respectively. If they are omitted, the peer will see
   /// a "no status received" code with no reason.
   ///
   /// [close code]: https://tools.ietf.org/html/rfc6455#section-7.1.5
   /// [reason]: https://tools.ietf.org/html/rfc6455#section-7.1.6
   Future close([int closeCode, String closeReason]) =>
       _webSocket.close(closeCode, closeReason);
 }