Re-write _BufferList to keep an internal Uint8List buffer, that will grow on demand.

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";
 
 class _WebSocketMessageType {
   static const int NONE = 0;
@@ skipping 259 matching lines @@
     }
   }
 
   void _messageFrameEnd(EventSink sink) {
     if (_fin) {
       switch (_currentMessageType) {
         case _WebSocketMessageType.TEXT:
           sink.add(_buffer.toString());
           break;
         case _WebSocketMessageType.BINARY:
-          if (_buffer.length == 0) {
-            sink.add(const []);
-          } else {
-            sink.add(_buffer.readBytes(_buffer.length));
-          }
+          sink.add(_buffer.readBytes());
           break;
       }
       _buffer = null;
       _currentMessageType = _WebSocketMessageType.NONE;
     }
     _prepareForNextFrame();
   }
 
   void _controlFrameEnd(EventSink sink) {
     switch (_opcode) {
@@ skipping 449 matching lines @@
           code == WebSocketStatus.RESERVED_1015) {
         throw new WebSocketException("Reserved status code $code");
       }
       _outCloseCode = code;
       _outCloseReason = reason;
       _writeClosed = true;
     }
     return _sink.close();
   }
 }