Move examples to //sky/sdk/example

sky/sdk/example/raw/painting.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:sky' as sky;
 import 'dart:math' as math;
 import 'dart:typed_data';
 
 void beginFrame(double timeStamp) {
   sky.Size size = new sky.Size(sky.view.width, sky.view.height);
@@ skipping 73 matching lines @@
   paint.setDrawLooper(builder.build());
   canvas.drawCircle(sky.Point.origin, radius, paint);
 
   sky.view.picture = recorder.endRecording();
 }
 
 void main() {
   sky.view.setBeginFrameCallback(beginFrame);
   sky.view.scheduleFrame();
 }