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

tests/standalone/io/http_server_early_client_close_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";
 import "dart:isolate";
 
 void sendData(List<int> data, int port) {
   Socket.connect("127.0.0.1", port).then((socket) {
     socket.listen((data) {
         Expect.fail("No data response was expected");
       });
-    socket.writeBytes(data);
+    socket.add(data);
     socket.close();
     socket.done.then((_) {
       socket.destroy();
     });
   });
 }
 
 class EarlyCloseTest {
   EarlyCloseTest(this.data,
                  String this.exception,
@@ skipping 131 matching lines @@
           socket.done.catchError((_) {});
         });
   });
 }
 
 void main() {
   testEarlyClose1();
   testEarlyClose2();
   testEarlyClose3();
 }