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

sky/sdk/lib/rendering/block.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' as math;
 
 import 'box.dart';
 import 'object.dart';
 
 class BlockParentData extends BoxParentData with ContainerParentDataMixin<RenderBox> { }
@@ skipping 82 matching lines @@
     }
     size = new Size(width, constraints.constrainHeight(y));
     assert(size.width < double.INFINITY);
     assert(size.height < double.INFINITY);
   }
 
   void hitTestChildren(HitTestResult result, { Point position }) {
     defaultHitTestChildren(result, position: position);
   }
 
-  void paint(RenderObjectDisplayList canvas) {
+  void paint(RenderCanvas canvas) {
     defaultPaint(canvas);
   }
 
 }