[infra] Translate _sources.gypi files to _sources.gni files

sdk/lib/async/async_sources.gni

Index: sdk/lib/async/async_sources.gni
diff --git a/sdk/lib/async/async_sources.gni b/sdk/lib/async/async_sources.gni
new file mode 100644
index 0000000000000000000000000000000000000000..3299cd405003ff1ed38ffc0f8a8d538dfd02d5fe
--- /dev/null
+++ b/sdk/lib/async/async_sources.gni
@@ -0,0 +1,23 @@
+# Copyright (c) 2017, 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:async library.
+async_sdk_sources = [
+  "async.dart",
+
+  # The above file needs to be first as it lists the parts below.
+  "async_error.dart",
+  "broadcast_stream_controller.dart",
+  "deferred_load.dart",
+  "future.dart",
+  "future_impl.dart",
+  "schedule_microtask.dart",
+  "stream.dart",
+  "stream_controller.dart",
+  "stream_impl.dart",
+  "stream_pipe.dart",
+  "stream_transformers.dart",
+  "timer.dart",
+  "zone.dart",
+]