Move examples to //sky/sdk/example

sky/sdk/example/raw/spinning_image.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.
 
 import 'dart:math' as math;
 import 'dart:sky';
 
 import 'package:sky/mojo/net/image_cache.dart' as image_cache;
 
 double timeBase = null;
@@ skipping 53 matching lines @@
 
   return false;
 }
 
 void main() {
   image_cache.load(url1, handleImageLoad);
   image_cache.load(url1, handleImageLoad);
   view.setEventCallback(handleEvent);
   view.setBeginFrameCallback(beginFrame);
 }