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

sky/examples/rendering/touch_demo.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:math';
 import 'dart:sky';
 
 import 'package:sky/framework/app.dart';
 import 'package:sky/framework/rendering/box.dart';
 import 'package:sky/framework/rendering/object.dart';
@@ skipping 18 matching lines @@
   double radius = 0.0;
 
   Dot({ Color color }) : _paint = new Paint()..color = color;
 
   void update(PointerEvent event) {
     x = event.x;
     y = event.y;
     radius = 5 + (95 * event.pressure);
   }
 
-  void paint(RenderObjectDisplayList canvas) {
+  void paint(sky.Canvas canvas) {
     canvas.drawCircle(x, y, radius, _paint);
   }
 }
 
 class RenderTouchDemo extends RenderBox {
   Map<int, Dot> dots = new Map();
 
   RenderTouchDemo();
 
   void handleEvent(Event event, BoxHitTestEntry entry) {
@@ skipping 12 matching lines @@
         dots[event.pointer].update(event);
         break;
     }
     markNeedsPaint();
   }
 
   void performLayout() {
     size = constraints.constrain(Size.infinite);
   }
 
-  void paint(RenderObjectDisplayList canvas) {
+  void paint(sky.Canvas canvas) {
     Paint white = new Paint()..color = const Color(0xFFFFFFFF);
     canvas.drawRect(new Rect.fromSize(size), white);
     for (Dot dot in dots.values)
       dot.paint(canvas);
   }
 }
 
 AppView app;
 
 void main() {
   var para = new RenderParagraph(text: "Touch me!");
   var stack = new RenderStack(children: [
     new RenderTouchDemo(),
     para,
   ]);
   // Make the paragraph not fill the whole screen so it doesn't eat events.
   para.parentData..top = 40.0
                  ..left = 20.0;
   app = new AppView(stack);
 }