Remove onFrame callback

sky/sdk/lib/rendering/object.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 'dart:sky' show Point, Offset, Size, Rect, Color, Paint, Path;
 
 import 'package:sky/base/debug.dart';
 import 'package:sky/base/hit_test.dart';
@@ skipping 319 matching lines @@
       scheduler.ensureVisualUpdate();
     } else {
       assert(parent != null); // parent always exists on this path because the root node is a RenderView, which sets createNewDisplayList.
       if (parent is RenderObject) {
         (parent as RenderObject).markNeedsPaint(); // TODO(ianh): remove the cast once the analyzer is cleverer
       }
     }
   }
 
   static void flushPaint() {
+    sky.tracing.begin('RenderObject.flushPaint');
+    _debugDoingPaint = true;
     try {
-      _debugDoingPaint = true;
       List<RenderObject> dirtyNodes = _nodesNeedingPaint;
       _nodesNeedingPaint = new List<RenderObject>();
       for (RenderObject node in dirtyNodes..sort((a, b) => a.depth - b.depth)) {
         if (node._needsPaint && node.attached)
           node._updatePaintingCanvas();
       };
       assert(_nodesNeedingPaint.length == 0);
     } finally {
       _debugDoingPaint = false;
+      sky.tracing.end('RenderObject.flushPaint');
     }
   }
 
   void _updatePaintingCanvas() {
     assert(!_needsLayout);
     assert(createNewDisplayList);
     sky.PictureRecorder recorder = new sky.PictureRecorder();
     PaintingCanvas canvas = new PaintingCanvas(recorder, paintBounds);
     _needsPaint = false;
     try {
@@ skipping 338 matching lines @@
     int count = 1;
     ChildType child = _firstChild;
     while (child != null) {
       result += '${prefix}child ${count}: ${child.toString(prefix)}';
       count += 1;
       child = child.parentData.nextSibling;
     }
     return result;
   }
 }