Make rendering use PaintingNodes for increased efficiency.

sky/tests/resources/display_list.dart

Index: sky/tests/resources/display_list.dart
diff --git a/sky/tests/resources/display_list.dart b/sky/tests/resources/display_list.dart
index 248cb1269dd9acfecbc1cb029c81d3c8fb7d42ac..a22fe980a9d482b480d3e268e7b37f80846897c3 100644
--- a/sky/tests/resources/display_list.dart
+++ b/sky/tests/resources/display_list.dart
@@ -14,7 +14,7 @@ typedef void Logger (String s);
 class TestPaintingCanvas extends PaintingCanvas {
   TestPaintingCanvas(sky.PictureRecorder recorder, Size size, this.logger, { this.indent: '' })
     : size = size,
-      super(recorder, size) {
+      super(recorder, Point.origin & size) {
     log("TestPaintingCanvas() constructor: ${size.width} x ${size.height}");
   }