anchor.diff:      if (!excludeChildren) {
         for (var i = 0; i < element.visualChildCount; i++) {
           var e = element.getVisualChild(i);
  -        ctx.save();
           _borderElement(ctx, e, false, filter);
  -        ctx.restore();
         }
       }
  -    ctx.restore();
     }
   
     static void _borderElementCore(CanvasRenderingContext2D ctx, PElement element) {
  
positive.code:     } else {
        ctx.strokeStyle = 'orange';
      }
      ctx.strokeRect(0, 0, element.width, element.height);
    }
  }
  
negative.code:   }
  
    static void _borderElement(CanvasRenderingContext2D ctx, PElement element, [bool excludeChildren = false, core.Predicate<PElement> filter = null]) {
      if (filter == null || filter(element)) {
        _borderElementCore(ctx, element);
      }
  