Decouple Canvas from DisplayList and map Picture and PictureRecorder more directly to their Skia co…

sky/examples/rendering/touch_demo.dart

Index: sky/examples/rendering/touch_demo.dart
diff --git a/sky/examples/rendering/touch_demo.dart b/sky/examples/rendering/touch_demo.dart
index 895cc60b54822c61527e2d018920db38f2ac8334..1773526d0f2633f32bd3486f4b068eb7399d0e73 100644
--- a/sky/examples/rendering/touch_demo.dart
+++ b/sky/examples/rendering/touch_demo.dart
@@ -36,7 +36,7 @@ class Dot {
     radius = 5 + (95 * event.pressure);
   }
 
-  void paint(RenderObjectDisplayList canvas) {
+  void paint(RenderCanvas canvas) {
     canvas.drawCircle(x, y, radius, _paint);
   }
 }
@@ -69,7 +69,7 @@ class RenderTouchDemo extends RenderBox {
     size = constraints.constrain(Size.infinite);
   }
 
-  void paint(RenderObjectDisplayList canvas) {
+  void paint(RenderCanvas canvas) {
     Paint white = new Paint()..color = const Color(0xFFFFFFFF);
     canvas.drawRect(new Rect.fromSize(size), white);
     for (Dot dot in dots.values)