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

sky/examples/game/lib/node_with_size.dart

-part of sprites;
-
-/// The super class of any [Node] that has a size.
-///
-/// NodeWithSize adds the ability for a node to have a size and a pivot point.
-abstract class NodeWithSize extends Node {
-
-  /// Changing the size will affect the size of the rendering of the node.
-  ///
-  ///     myNode.size = new Size(1024.0, 1024.0);
-  Size size;
-
-  /// The normalized point which the node is transformed around.
-  ///
-  ///     // Position myNode from is middle top
-  ///     myNode.pivot = new Point(0.5, 0.0);
-  Point pivot;
-
-  /// Creates a new NodeWithSize.
-  ///
-  /// The default [size] is zero and the default [pivot] point is the origin. Subclasses may change the default values.
-  ///
-  ///     var myNodeWithSize = new NodeWithSize(new Size(1024.0, 1024.0));
-  NodeWithSize([Size this.size, Point this.pivot]) {
-    if (size == null) size = Size.zero;
-    if (pivot == null) pivot = Point.origin;
-  }
-
-  /// Call this method in your [paint] method if you want the origin of your drawing to be the top left corner of the
-  /// node's bounding box.
-  ///
-  /// If you use this method you will need to save and restore your canvas at the beginning and
-  /// end of your [paint] method.
-  ///
-  ///     void paint(RenderCanvas canvas) {
-  ///       canvas.save();
-  ///       applyTransformForPivot(canvas);
-  ///
-  ///       // Do painting here
-  ///
-  ///       canvas.restore();
-  ///     }
-  void applyTransformForPivot(RenderCanvas canvas) {
-    if (pivot.x != 0 || pivot.y != 0) {
-      double pivotInPointsX = size.width * pivot.x;
-      double pivotInPointsY = size.height * pivot.y;
-      canvas.translate(-pivotInPointsX, -pivotInPointsY);
-    }
-  }
-
-  bool isPointInside (Point nodePoint) {
-
-    double minX = -size.width * pivot.x;
-    double minY = -size.height * pivot.y;
-    double maxX = minX + size.width;
-    double maxY = minY + size.height;
-    return (nodePoint.x >= minX && nodePoint.x < maxX &&
-            nodePoint.y >= minY && nodePoint.y < maxY);
-  }
-}