Ensure proper response to chrome client_max_window_bits

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";
 const String _clientNoContextTakeover = "client_no_context_takeover";
 const String _serverNoContextTakeover = "server_no_context_takeover";
 const String _clientMaxWindowBits = "client_max_window_bits";
@@ skipping 19 matching lines @@
   static const int PING = 9;
   static const int PONG = 10;
   static const int RESERVED_B = 11;
   static const int RESERVED_C = 12;
   static const int RESERVED_D = 13;
   static const int RESERVED_E = 14;
   static const int RESERVED_F = 15;
 }
 
 /**
+ *  Stores the header and integer value derived from negotiation of
+ *  client_max_window_bits and server_max_window_bits. headerValue will be
+ *  set in the Websocket response headers.
+ */
+class _CompressionMaxWindowBits {
+  String headerValue;
+  int maxWindowBits;
+  _CompressionMaxWindowBits([this.headerValue, this.maxWindowBits]);
+  String toString() => headerValue;
+}
+
+/**
  * The web socket protocol transformer handles the protocol byte stream
  * which is supplied through the [:handleData:]. As the protocol is processed,
  * it'll output frame data as either a List<int> or String.
  *
  * Important information about usage: Be sure you use cancelOnError, so the
  * socket will be closed when the processor encounter an error. Not using it
  * will lead to undefined behaviour.
  */
 // TODO(ajohnsen): make this transformer reusable?
 class _WebSocketProtocolTransformer implements StreamTransformer, EventSink {
@@ skipping 401 matching lines @@
       }).then(upgrade);
     } else {
       return upgrade(null);
     }
   }
 
   static _WebSocketPerMessageDeflate _negotiateCompression(HttpRequest request,
       HttpResponse response, CompressionOptions compression) {
     var extensionHeader = request.headers.value("Sec-WebSocket-Extensions");
 
-    if (extensionHeader == null) {
-      extensionHeader = "";
-    }
+    extensionHeader ??= "";
 
     var hv = HeaderValue.parse(extensionHeader, valueSeparator: ',');
     if (compression.enabled && hv.value == _WebSocketImpl.PER_MESSAGE_DEFLATE) {
       var info = compression._createHeader(hv);
 
-      response.headers.add("Sec-WebSocket-Extensions", info[0]);
+      response.headers.add("Sec-WebSocket-Extensions", info.headerValue);
       var serverNoContextTakeover =
           hv.parameters.containsKey(_serverNoContextTakeover);
       var clientNoContextTakeover =
           hv.parameters.containsKey(_clientNoContextTakeover);
       var deflate = new _WebSocketPerMessageDeflate(
           serverNoContextTakeover: serverNoContextTakeover,
           clientNoContextTakeover: clientNoContextTakeover,
-          serverMaxWindowBits: info[1],
-          clientMaxWindowBits: info[1],
+          serverMaxWindowBits: info.maxWindowBits,
+          clientMaxWindowBits: info.maxWindowBits,
           serverSide: true);
 
       return deflate;
     }
 
     return null;
   }
 
   static bool _isUpgradeRequest(HttpRequest request) {
     if (request.method != "GET") {
@@ skipping 742 matching lines @@
     return code != null &&
         (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));
   }
 }