Make rendering use PaintingNodes for increased efficiency.

sky/sdk/lib/rendering/box.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 'dart:sky' as sky;
 
 import 'package:vector_math/vector_math.dart';
 
 import '../base/debug.dart';
@@ skipping 411 matching lines @@
     assert(RenderObject.debugDoingLayout);
     assert((sizedByParent && debugDoingThisResize) ||
            (!sizedByParent && debugDoingThisLayout));
     if (value is _DebugSize) {
       assert(value._canBeUsedByParent);
       assert(value._owner.parent == this);
     }
     _size = inDebugBuild ? new _DebugSize(value, this, debugCanParentUseSize) : value;
   }
 
+  Rect get paintBounds => Point.origin & size;
+
   String debugDescribeSettings(String prefix) => '${super.debugDescribeSettings(prefix)}${prefix}size: ${size}\n';
 }
 
 class RenderProxyBox extends RenderBox with RenderObjectWithChildMixin<RenderBox> {
 
   // ProxyBox assumes the child will be at 0,0 and will have the same size
 
   RenderProxyBox([RenderBox child = null]) {
     this.child = child;
   }
@@ skipping 902 matching lines @@
     return true;
   }
 
   void paint(PaintingCanvas canvas, Offset offset) {
     if (child != null)
       canvas.paintChild(child, offset.toPoint());
   }
 
   void paintFrame() {
     sky.tracing.begin('RenderView.paintFrame');
-    RenderObject.debugDoingPaint = true;
     try {
       sky.PictureRecorder recorder = new sky.PictureRecorder();
-      PaintingCanvas canvas = new PaintingCanvas(recorder, _size);
-      paint(canvas, Offset.zero);
+      PaintingCanvas canvas = new PaintingCanvas(recorder, paintBounds);
+      canvas.drawPaintingNode(paintingNode);
       sky.view.picture = recorder.endRecording();
     } finally {
-      RenderObject.debugDoingPaint = false;
       sky.tracing.end('RenderView.paintFrame');
     }
   }
 
+  Rect get paintBounds => Point.origin & size;
 }
 
 // HELPER METHODS FOR RENDERBOX CONTAINERS
 abstract class RenderBoxContainerDefaultsMixin<ChildType extends RenderBox, ParentDataType extends ContainerParentDataMixin<ChildType>> implements ContainerRenderObjectMixin<ChildType, ParentDataType> {
 
   // This class, by convention, doesn't override any members of the superclass.
   // It only provides helper functions that subclasses can call.
 
   double defaultComputeDistanceToFirstActualBaseline(TextBaseline baseline) {
     assert(!needsLayout);
@@ skipping 44 matching lines @@
 
   void defaultPaint(PaintingCanvas canvas, Offset offset) {
     RenderBox child = firstChild;
     while (child != null) {
       assert(child.parentData is ParentDataType);
       canvas.paintChild(child, child.parentData.position + offset);
       child = child.parentData.nextSibling;
     }
   }
 }