Move fn.dart into /sky/framework

sky/examples/fn/lib/event.dart

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-part of fn;
-
-class EventHandler {
-  final String type;
-  final sky.EventListener listener;
-
-  EventHandler(this.type, this.listener);
-}
-
-class EventMap {
-  final List<EventHandler> _handlers = new List<EventHandler>();
-
-  void listen(String type, sky.EventListener listener) {
-    assert(listener != null);
-    _handlers.add(new EventHandler(type, listener));
-  }
-
-  void addAll(EventMap events) {
-    _handlers.addAll(events._handlers);
-  }
-}