Add dart:collection_dev library.

sdk/lib/collection_dev/collection_dev_sources.gypi

Index: sdk/lib/collection_dev/collection_dev_sources.gypi
diff --git a/runtime/lib/async_sources.gypi b/sdk/lib/collection_dev/collection_dev_sources.gypi
similarity index 72%
copy from runtime/lib/async_sources.gypi
copy to sdk/lib/collection_dev/collection_dev_sources.gypi
index d1c0711679a7189610e28d878b4f8825aae0a3c6..f83a837a42568d1f3e2b23009023969a4384253d 100644
--- a/runtime/lib/async_sources.gypi
+++ b/sdk/lib/collection_dev/collection_dev_sources.gypi
@@ -2,9 +2,10 @@
 # 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.
+# This file contains all sources for the dart:collection-dev library.
 {
   'sources': [
-    'timer_patch.dart',
+    'empty.dart',
   ],
 }
+