When a connection is upgraded, don't return it as idle.

sdk/lib/io/http_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 int _OUTGOING_BUFFER_SIZE = 8 * 1024;
 
 class _HttpIncoming extends Stream<List<int>> {
   final int _transferLength;
@@ skipping 244 matching lines @@
               ..addAll(this.redirects)
               ..add(new _RedirectInfo(statusCode, method, url));
           return request.close();
         });
   }
 
   StreamSubscription<List<int>> listen(void onData(List<int> event),
                                        {Function onError,
                                         void onDone(),
                                         bool cancelOnError}) {
+    if (_incoming.upgraded) {
+      // If upgraded, the connection is already 'removed' form the client.
+      // Since listening to upgraded data is 'bogus', simply close and
+      // return empty stream subscription.
+      _httpRequest._httpClientConnection.destroy();
+      return new Stream.fromIterable([]).listen(null, onDone: onDone);
+    }
     var stream = _incoming;
     if (headers.value(HttpHeaders.CONTENT_ENCODING) == "gzip") {
       stream = stream.transform(GZIP.decoder);
     }
     return stream.listen(onData,
                          onError: onError,
                          onDone: onDone,
                          cancelOnError: cancelOnError);
   }
 
@@ skipping 1077 matching lines @@
     _streamFuture = outgoing.done
         .then((s) {
           // Request sent, set up response completer.
           _nextResponseCompleter = new Completer();
 
           // Listen for response.
           _nextResponseCompleter.future
               .then((incoming) {
                 _currentUri = null;
                 incoming.dataDone.then((closing) {
+                  if (incoming.upgraded) {
+                    _httpClient._connectionClosed(this);
+                    startTimer();
+                    return;
+                  }
                   if (closed) return;
                   if (!closing &&
                       !_dispose &&
                       incoming.headers.persistentConnection &&
                       request.persistentConnection) {
                     // Return connection, now we are done.
                     _httpClient._returnConnection(this);
                     _subscription.resume();
                   } else {
                     destroy();
@@ skipping 1344 matching lines @@
   const _RedirectInfo(this.statusCode, this.method, this.location);
 }
 
 String _getHttpVersion() {
   var version = Platform.version;
   // Only include major and minor version numbers.
   int index = version.indexOf('.', version.indexOf('.') + 1);
   version = version.substring(0, index);
   return 'Dart/$version (dart:io)';
 }