Buffer the entire http header to one packet, and buffer other data in chunks of 4-16 kb.

tests/standalone/io/http_content_length_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 "dart:isolate";
 import "dart:io";
 
 void testNoBody(int totalConnections, bool explicitContentLength) {
   var errors = 0;
   HttpServer.bind("127.0.0.1", 0, totalConnections).then((server) {
@@ skipping 112 matching lines @@
           })
           .then((response) {
             Expect.equals("2", response.headers.value('content-length'));
             Expect.equals(2, response.contentLength);
             response.listen(
                 (d) {},
                 onDone: () {
                   if (++clientCount == totalConnections) {
                     client.close();
                   }
+                },
+                onError: (error) {
+                  // Undefined what server response sends.
                 });
           });
     }
   });
 }
 
 void testBodyChunked(int totalConnections, bool useHeader) {
   HttpServer.bind("127.0.0.1", 0, totalConnections).then((server) {
     server.listen(
         (HttpRequest request) {
@@ skipping 89 matching lines @@
 
 void main() {
   testNoBody(5, false);
   testNoBody(5, true);
   testBody(5, false);
   testBody(5, true);
   testBodyChunked(5, false);
   testBodyChunked(5, true);
   testSetContentLength();
 }