Move _StreamSinkImpl from dart:io to dart:async as StreamSinkAdapter.

sdk/lib/io/websocket_impl.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.
 
 part of dart.io;
 
 const String _webSocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
 
 // Matches _WebSocketOpcode.
 class _WebSocketMessageType {
@@ skipping 846 matching lines @@
         }
         var protocol = response.headers.value('Sec-WebSocket-Protocol');
         return response.detachSocket()
             .then((socket) => new _WebSocketImpl._fromSocket(socket, protocol));
       });
   }
 
   _WebSocketImpl._fromSocket(this._socket, this.protocol,
                              [this._serverSide = false]) {
     _consumer = new _WebSocketConsumer(this, _socket);
-    _sink = new _StreamSinkImpl(_consumer);
+    _sink = new StreamSinkAdapter(_consumer);
     _readyState = WebSocket.OPEN;
 
     var transformer = new _WebSocketProtocolTransformer(_serverSide);
     _subscription = _socket.transform(transformer).listen(
         (data) {
           if (data is _WebSocketPing) {
             if (!_writeClosed) _consumer.add(new _WebSocketPong(data.payload));
           } else if (data is _WebSocketPong) {
             // Simply set pingInterval, as it'll cancel any timers.
             pingInterval = _pingInterval;
@@ skipping 107 matching lines @@
            (code < WebSocketStatus.NORMAL_CLOSURE ||
             code == WebSocketStatus.RESERVED_1004 ||
             code == WebSocketStatus.NO_STATUS_RECEIVED ||
             code == WebSocketStatus.ABNORMAL_CLOSURE ||
             (code > WebSocketStatus.INTERNAL_SERVER_ERROR &&
              code < WebSocketStatus.RESERVED_1015) ||
             (code >= WebSocketStatus.RESERVED_1015 &&
              code < 3000));
   }
 }