Add a small LED interface and demo app.

dart/examples/led/led.dart

Index: dart/examples/led/led.dart
diff --git a/dart/examples/led/led.dart b/dart/examples/led/led.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c122e676da5d3840920fe1cac49fc940783fe3ba
--- /dev/null
+++ b/dart/examples/led/led.dart
@@ -0,0 +1,16 @@
+// Copyright (c) 2016, the Dartino 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.md file.
+
+import "dart:dartino";
+import "dart:async";
+import "package:lk/leds.dart";
+
+void main() {
+  // Start up some timers. Note that timers in dartino are based on fibers,
+  // so even though the main fiber ends, the timers will keep running.
+  new Timer.periodic(const Duration(milliseconds: 50), (_) => LED0.toggle());
+  new Timer.periodic(const Duration(milliseconds: 100), (_) => LED1.toggle());
+  new Timer.periodic(const Duration(milliseconds: 75), (_) => LED2.toggle());
+  new Timer.periodic(const Duration(milliseconds: 333), (_) => LED3.toggle());
+}