Remove StreamSink(replaced by EventSink) and make IOSink extend EventSink.

tests/standalone/io/http_compression_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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 import 'package:expect/expect.dart';
 import 'dart:io';
 import 'dart:typeddata';
 
 void testServerCompress() {
   void test(List<int> data) {
     HttpServer.bind().then((server) {
       server.listen((request) {
-        request.response.writeBytes(data);
+        request.response.add(data);
         request.response.close();
       });
       var client = new HttpClient();
       client.get("localhost", server.port, "/")
           .then((request) {
             request.headers.set(HttpHeaders.ACCEPT_ENCODING, "gzip,deflate");
             return request.close();
           })
           .then((response) {
             Expect.equals("gzip",
@@ skipping 55 matching lines @@
   test('deflate  ,  gzip', true);
   test('abc,deflate  ,  gzip,def,,,ghi  ,jkl', true);
   test('xgzip', false);
   test('gzipx;', false);
 }
 
 void main() {
   testServerCompress();
   testAcceptEncodingHeader();
 }