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

sky/examples/game/lib/game_demo_world.dart

 part of game;
 
 const double _steeringThreshold = 0.0;
 const double _steeringMax = 150.0;
 
 // Random generator
 Math.Random _rand = new Math.Random();
 
 const double _gameSizeWidth = 1024.0;
 const double _gameSizeHeight = 1024.0;
@@ skipping 369 matching lines @@
     _starScales = [];
     _opacity = [];
 
     for (int i  = 0; i < _numStars; i++) {
       _starPositions.add(new Point(_rand.nextDouble() * _gameSizeWidth, _rand.nextDouble() * _gameSizeHeight));
       _starScales.add(_rand.nextDouble());
       _opacity.add(_rand.nextDouble() * 0.5 + 0.5);
     }
   }
 
-  void paint(PictureRecorder canvas) {
+  void paint(RenderCanvas canvas) {
     // Setup paint object for opacity and transfer mode
     Paint paint = new Paint();
     paint.setTransferMode(TransferMode.plus);
 
     double baseScaleX = 32.0/_img.width;
     double baseScaleY = 32.0/_img.height;
 
     // Draw each star
     for (int i = 0; i < _numStars; i++) {
       Point pos = _starPositions[i];
@@ skipping 68 matching lines @@
   double dy = a.y - b.y;
   if (dx < 0.0) dx = -dx;
   if (dy < 0.0) dy = -dy;
   if (dx > dy) {
     return dx + dy/2.0;
   }
   else {
     return dy + dx/2.0;
   }
 }