Split dart:builtin into dart:builtin and dart:io.

runtime/bin/io_sources.gypi

Index: runtime/bin/io_sources.gypi
diff --git a/runtime/bin/io_sources.gypi b/runtime/bin/io_sources.gypi
new file mode 100644
index 0000000000000000000000000000000000000000..5405d47b90928acbeb99bd575cda72d68cefdad2
--- /dev/null
+++ b/runtime/bin/io_sources.gypi
@@ -0,0 +1,31 @@
+# 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.
+
+# This file contains all sources for the dart:io library.
+{
+  'sources': [
+    'buffer_list.dart',
+    'chunked_stream.dart',
+    'directory.dart',
+    'directory_impl.dart',
+    'eventhandler.dart',
+    'file.dart',
+    'file_impl.dart',
+    'input_stream.dart',
+    'list_stream.dart',
+    'output_stream.dart',
+    'stream_util.dart',
+    'string_stream.dart',
+    'platform.dart',
+    'platform_impl.dart',
+    'process.dart',
+    'process_impl.dart',
+    'socket.dart',
+    'socket_impl.dart',
+    'socket_stream.dart',
+    'stdio.dart',
+    'timer.dart',
+    'timer_impl.dart',
+  ],
+}