Add a sleep function to dart:io

runtime/platform/platform_sources.gypi

Index: runtime/platform/platform_sources.gypi
diff --git a/runtime/platform/platform_sources.gypi b/runtime/platform/platform_sources.gypi
index eadf674a1863d3b08d7a90a3dc9cc6fe78876398..5e2d50cb8615deaf78e3840a6232fb2f2326ea51 100644
--- a/runtime/platform/platform_sources.gypi
+++ b/runtime/platform/platform_sources.gypi
@@ -1,4 +1,4 @@
-# Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+# 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.
 
@@ -9,6 +9,10 @@
     'hashmap.cc',
     'json.cc',
     'floating_point_win.cc',
+    'platform_os_android.cc',
+    'platform_os_linux.cc',
+    'platform_os_macos.cc',
+    'platform_os_win.cc',
     'thread_android.cc',
     'thread_linux.cc',
     'thread_macos.cc',