Implementation of async-await transformation on js ast.

tests/language/syncstar_yieldstar_test.dart

Index: tests/language/syncstar_yieldstar_test.dart
diff --git a/tests/language/syncstar_yieldstar_test.dart b/tests/language/syncstar_yieldstar_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..9da39365d2fc174fc7cc4f3f1929dd82bc1224b9
--- /dev/null
+++ b/tests/language/syncstar_yieldstar_test.dart
@@ -0,0 +1,25 @@
+// Copyright (c) 2015, 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.
+
+import "package:expect/expect.dart";
+
+bar() sync* {
+  int i = 1;
+  int j = 1;
+  while (true) {
+    yield i;
+    j = i + j;
+    i = j - i;
+  }
+}
+
+foo() sync* {
+  yield* [1, 2, 3];
+  yield null;
+  yield* bar();
+}
+
+main () async {
+  Expect.listEquals([1, 2, 3, null, 1, 1, 2, 3, 5], foo().take(9).toList());
+}