Support auto-drain of HttpRequest data.

tests/standalone/io/http_session_test.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.
 
 import "package:expect/expect.dart";
 import 'dart:async';
 import 'dart:io';
 
 const SESSION_ID = "DARTSESSID";
 
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       Expect.setEquals(new Set.from(clientSessions), sessions);
       server.close();
       client.close();
     });
   });
 }
 
 void testTimeout(int sessionCount) {
   var client = new HttpClient();
   HttpServer.bind("127.0.0.1", 0).then((server) {
-    server.sessionTimeout = 0;
+    server.sessionTimeout = 1;
     var timeouts = [];
     server.listen((request) {
       var c = new Completer();
       timeouts.add(c.future);
       request.session.onTimeout = () {
         c.complete(null);
       };
       request.response.close();
     });
 
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       });
   });
 }
 
 void main() {
   testSessions(1);
   testTimeout(5);
   testSessionsData();
   testSessionsDestroy();
 }