Revert "Add onClosed callbacks to HTTP output streams"

tests/standalone/io/http_stream_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 "dart:io";
-import "dart:uri";
-
-main() {
-  bool serverOnClosed = false;
-  bool clientOnClosed = false;
-
-  var server = new HttpServer();
-  server.listen("127.0.0.1", 0);
-  server.defaultRequestHandler = (request, response) {
-    request.inputStream.onData = request.inputStream.read;
-    request.inputStream.onClosed = () {
-      response.outputStream.onClosed = () => serverOnClosed = true;
-      response.outputStream.writeString("hello!");
-      response.outputStream.close();
-    };
-  };
-
-  var client = new HttpClient();
-    var connection = client.postUrl(new Uri.fromString("http://127.0.0.1:${server.port}"));
-    connection.onError = (e) => throw e;
-    connection.onRequest = (request) {
-      request.contentLength = "hello!".length;
-      request.outputStream.onError = (e) => throw e;
-      request.outputStream.onClosed = () => clientOnClosed = true;
-      request.outputStream.writeString("hello!");
-      request.outputStream.close();
-    };
-    connection.onResponse = (response) {
-      response.inputStream.onData = response.inputStream.read;
-      response.inputStream.onClosed = () {
-        Expect.isTrue(serverOnClosed && clientOnClosed);
-        server.close();
-        client.shutdown();
-      };
-    };
-}