Compile package:js.{rest, spread} helpers

test/codegen/varargs.dart

Index: test/codegen/varargs.dart
diff --git a/test/codegen/varargs.dart b/test/codegen/varargs.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f97ac58a9e485988dc87f0b7fbab40377714660c
--- /dev/null
+++ b/test/codegen/varargs.dart
@@ -0,0 +1,12 @@
+import 'package:js/src/varargs.dart' as js;
+import 'package:js/src/varargs.dart' show rest, spread;
+
+varargsTest(x, @js.rest others) {
+  var args = [1, others];
+  x.call(js.spread(args));
+}
+
+varargsTest2(x, @rest others) {
+  var args = [1, others];
+  x.call(spread(args));
+}