Ink splashes should start at the touch point

sky/examples/raw/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 24 matching lines @@
   void paint(RenderObjectDisplayList canvas) {
     canvas.drawCircle(x, y, radius, _paint);
   }
 }
 
 class RenderTouchDemo extends RenderBox {
   Map<int, Dot> dots = new Map();
 
   RenderTouchDemo();
 
-  void handleEvent(sky.Event event) {
+  void handleEvent(Event event, BoxHitTestData data) {
     switch (event.type) {
       case 'pointerdown':
         int color = colors[event.pointer.remainder(colors.length)];
         dots[event.pointer] = new Dot(color: color)..update(event);
         break;
       case 'pointerup':
         dots.remove(event.pointer);
         break;
       case 'pointercancel':
         dots = new Map();
@@ skipping 14 matching lines @@
       dot.paint(canvas);
     });
   }
 }
 
 AppView app;
 
 void main() {
   app = new AppView(new RenderTouchDemo());
 }