Reapply change to enable a couple of tests that were not run because they were named incorrectly.

sdk/lib/io/http_impl.dart

 // Copyright (c) 2012, 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;
 
 // The close queue handles graceful closing of HTTP connections. When
 // a connection is added to the queue it will enter a wait state
 // waiting for all data written and possibly socket shutdown from
 // peer.
@@ skipping 1519 matching lines @@
   void _checkSocketDone() {
     if (_isAllDone) {
       // If we are done writing the response, and either the server
       // has closed or the connection is not persistent, we must
       // close.
       if (_isReadClosed || !_response.persistentConnection) {
         this.onClosed = () {
           _client._closedSocketConnection(_socketConn);
         };
         _client._closeQueue.add(this);
-      } else {
+      } else if (_socket != null) {
         _client._returnSocketConnection(_socketConn);
         _socket = null;
         _socketConn = null;
         assert(_pendingRedirect == null || _pendingRetry == null);
         if (_pendingRedirect != null) {
           _doRedirect(_pendingRedirect);
           _pendingRedirect = null;
         } else if (_pendingRetry != null) {
           _doRetry(_pendingRetry);
           _pendingRetry = null;
@@ skipping 749 matching lines @@
 
 
 class _RedirectInfo implements RedirectInfo {
   const _RedirectInfo(int this.statusCode,
                       String this.method,
                       Uri this.location);
   final int statusCode;
   final String method;
   final Uri location;
 }