Support auto-drain of HttpRequest data.

tests/standalone/io/http_parser_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:math';
 import 'dart:typed_data';
 import 'dart:isolate';
 import 'dart:uri';
@@ skipping 56 matching lines @@
           expectedHeaders.forEach(
               (String name, String value) =>
               Expect.equals(value, headers[name][0]));
         }
         incoming.listen(
             (List<int> data) {
               Expect.isFalse(upgraded);
               bytesReceived += data.length;
             },
             onDone: () {
-              Expect.isFalse(upgraded);
               port2.close();
               Expect.equals(expectedMethod, method);
               Expect.stringEquals(expectedUri, uri.toString());
               Expect.equals(expectedVersion, headers.protocolVersion);
               if (upgrade) {
                 Expect.equals(0, bytesReceived);
                 // port1 is closed by the listener on the detached data.
               } else {
                 Expect.equals(expectedBytesReceived, bytesReceived);
               }
             });
 
         if (upgraded) {
           port1.close();
           httpParser.detachIncoming().listen(
               (List<int> data) {
                 unparsedBytesReceived += data.length;
               },
               onDone: () {
                 Expect.equals(unparsedLength, unparsedBytesReceived);
                 port2.close();
               });
         }
 
         incoming.dataDone.then((_) {
           port1.close();
-          Expect.isFalse(upgraded);
         });
       });
 
       method = null;
       uri = null;
       headers = null;
       bytesReceived = 0;
       unparsedBytesReceived = 0;
       upgraded = false;
     }
@@ skipping 752 matching lines @@
 0123456789012345678901234567890\r
 0\r\n\r\n""";
     _testParseInvalidResponse(response);
   }
 }
 
 
 void main() {
   HttpParserTest.runAllTests();
 }