Move sky/examples to sky/sdk/lib/example, and code changes to support that change. Fixes T277.

sky/examples/rendering/spinning_flex.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 'package:sky/base/scheduler.dart';
-import 'package:sky/rendering/box.dart';
-import 'package:sky/rendering/flex.dart';
-import 'package:sky/rendering/sky_binding.dart';
-import 'package:vector_math/vector_math.dart';
-
-import '../lib/solid_color_box.dart';
-
-double timeBase;
-RenderTransform transformBox;
-
-void main() {
-  RenderFlex flexRoot = new RenderFlex(direction: FlexDirection.vertical);
-
-  void addFlexChildSolidColor(RenderFlex parent, sky.Color backgroundColor, { int flex: 0 }) {
-    RenderSolidColorBox child = new RenderSolidColorBox(backgroundColor);
-    parent.add(child);
-    child.parentData.flex = flex;
-  }
-
-  addFlexChildSolidColor(flexRoot, const sky.Color(0xFFFF00FF), flex: 1);
-  addFlexChildSolidColor(flexRoot, const sky.Color(0xFFFFFF00), flex: 2);
-  addFlexChildSolidColor(flexRoot, const sky.Color(0xFF00FFFF), flex: 1);
-
-  transformBox = new RenderTransform(child: flexRoot, transform: new Matrix4.identity());
-
-  RenderPadding root = new RenderPadding(padding: new EdgeDims.all(20.0), child: transformBox);
-
-  new SkyBinding(root: root);
-
-  addPersistentFrameCallback(rotate);
-}
-
-void rotate(double timeStamp) {
-  if (timeBase == null)
-    timeBase = timeStamp;
-  double delta = (timeStamp - timeBase) / 1000; // radians
-
-  transformBox.setIdentity();
-  transformBox.translate(transformBox.size.width / 2.0, transformBox.size.height / 2.0);
-  transformBox.rotateZ(delta);
-  transformBox.translate(-transformBox.size.width / 2.0, -transformBox.size.height / 2.0);
-}