isolates refactor: this change introduces 'dart:isolate' as a library. This is a

runtime/lib/isolate_sources.gypi

Index: runtime/lib/isolate_sources.gypi
diff --git a/runtime/lib/isolate_sources.gypi b/runtime/lib/isolate_sources.gypi
new file mode 100644
index 0000000000000000000000000000000000000000..2aa46c0a6d1a59d3bcb5e57e012827bb5a8e7826
--- /dev/null
+++ b/runtime/lib/isolate_sources.gypi
@@ -0,0 +1,12 @@
+# 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:isolate library.
+{
+  'sources': [
+    '../../lib/isolate/isolate_api.dart',
+    'isolate.dart',
+    'isolate.cc',
+  ],
+}