anchor.diff:  
     void _setMouse(core.Coordinate value) {
       _mouseLocation = value;
  -    requestFrame();
  +    //requestFrame();
     }
   }
  
positive.code:     }
    }
  
    bool _onFrame(num highResTime){
      _frameRequested = false;
    }
  
    void _canvas_mouseMove(MouseEvent e){
  
negative.code: main(){
    CanvasElement canvas = document.query("#content");
    final demo = new QrDemo(canvas);
    demo._setValue("hello world");
    demo.requestFrame();
  }
  
  class QrDemo{
    static final int typeNumber = 10;
    static final int size = typeNumber * 4 + 17;
    static final int scale = 5;
  
    final List<bool> _squares;
  
    final CanvasElement _canvas;
    CanvasRenderingContext2D _ctx;
  
    core.Coordinate _mouseLocation;
    bool _frameRequested = false;
  