Remove SendPortSync and ReceivePortSync.

third_party/pkg/js/build.dart

-#!/usr/bin/env dart
-// Copyright (c) 2012, 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.
-
-library build;
-
-import 'tools/create_bootstrap.dart' as createBootstrap;
-import 'dart:io';
-
-void main(List<String> arguments) {
-  final scriptPath = new Path(Platform.script).directoryPath;
-  final libPath = scriptPath.append('lib');
-
-  final changedOpt = "--changed=${libPath.append('js.dart')}";
-  for (String arg in arguments) {
-    if (arg == changedOpt) {
-      createBootstrap.create(libPath);
-    }
-  }
-}