Add Canvas.drawPicture

sky/examples/raw/draw_picture_into_canvas.sky

Index: sky/examples/raw/draw_picture_into_canvas.sky
diff --git a/sky/examples/raw/paint_element_into_displaylist.sky b/sky/examples/raw/draw_picture_into_canvas.sky
similarity index 73%
copy from sky/examples/raw/paint_element_into_displaylist.sky
copy to sky/examples/raw/draw_picture_into_canvas.sky
index c684836d0cdb75b0425a408041123de699bda9a2..95f9ca19926fc98460a5aec85ef6d859a0a38820 100644
--- a/sky/examples/raw/paint_element_into_displaylist.sky
+++ b/sky/examples/raw/draw_picture_into_canvas.sky
@@ -10,15 +10,19 @@ void main() {
 
   double width = window.innerWidth.toDouble();
   double height = window.innerHeight.toDouble();
+  PictureRecorder stampRecorder = new PictureRecorder(width, height);
+  root.paint(stampRecorder);
+  Picture stamp = stampRecorder.endRecording();
+
   PictureRecorder recorder = new PictureRecorder(width, height);
   Paint paint = new Paint()..setARGB(255, 0, 255, 0);
   recorder.drawCircle(50.0, 50.0, 50.0, paint);
   recorder.translate(10.0, 10.0);
-  root.paint(recorder);
+  recorder.drawPicture(stamp);
   recorder.translate(10.0, 10.0);
-  root.paint(recorder);
+  recorder.drawPicture(stamp);
   recorder.translate(10.0, 10.0);
-  root.paint(recorder);
+  recorder.drawPicture(stamp);
   document.rootPicture = recorder.endRecording();
 }
 </script>