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

sky/examples/raw/spinning_image.dart

Index: sky/examples/raw/spinning_image.dart
diff --git a/sky/examples/raw/spinning_image.dart b/sky/examples/raw/spinning_image.dart
index 1a6a8932ade3b67cb5c1f5ff1e85b58998c7265f..7bc5fc02208814d912171760e07a6202665623ff 100644
--- a/sky/examples/raw/spinning_image.dart
+++ b/sky/examples/raw/spinning_image.dart
@@ -15,14 +15,15 @@ String url2 = "http://i2.kym-cdn.com/photos/images/facebook/000/581/296/c09.jpg"
 void beginFrame(double timeStamp) {
   if (timeBase == null) timeBase = timeStamp;
   double delta = timeStamp - timeBase;
-  PictureRecorder canvas = new PictureRecorder(view.width, view.height);
+  PictureRecorder recorder = new PictureRecorder();
+  Canvas canvas = recorder.beginRecording(view.width, view.height);
   canvas.translate(view.width / 2.0, view.height / 2.0);
   canvas.rotate(math.PI * delta / 1800);
   canvas.scale(0.2, 0.2);
   Paint paint = new Paint()..color = const Color.fromARGB(255, 0, 255, 0);
   if (image != null)
     canvas.drawImage(image, -image.width / 2.0, -image.height / 2.0, paint);
-  view.picture = canvas.endRecording();
+  view.picture = recorder.endRecording();
   view.scheduleFrame();
 }