Merge all http-outgoing transfomers into _HttpOutgoing, including simpler(better) buffering.

tests/standalone/io/http_10_test.dart

 // (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.
 
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 import "package:expect/expect.dart";
@@ skipping 32 matching lines @@
       Socket.connect("127.0.0.1", server.port).then((socket) {
           socket.write("GET / HTTP/1.0\r\n\r\n");
 
           List<int> response = [];
           socket.listen(
               response.addAll,
               onDone: () {
                 count++;
                 socket.destroy();
                 String s = new String.fromCharCodes(response).toLowerCase();
-                Expect.isTrue(s.indexOf("\r\ncontent-length: 1\r\n") > 0);
                 Expect.equals(-1, s.indexOf("keep-alive"));
                 if (count < 10) {
                   makeRequest();
                 } else {
                   server.close();
                 }
               });
         });
     }
     makeRequest();
@@ skipping 157 matching lines @@
   });
 }
 
 
 void main() {
   testHttp10NoKeepAlive();
   testHttp10ServerClose();
   testHttp10KeepAlive();
   testHttp10KeepAliveServerCloses();
 }