anchor.diff:    @override
     ui.EngineLayer addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) {
       assert(optionsMask != null);
  -    builder.addPerformanceOverlay(optionsMask, overlayRect.shift(layerOffset));
  +    final Rect shiftedOverlayRect = layerOffset == Offset.zero ? overlayRect : overlayRect.shift(layerOffset);
  +    builder.addPerformanceOverlay(optionsMask, shiftedOverlayRect);
       builder.setRasterizerTracingThreshold(rasterizerThreshold);
       builder.setCheckerboardRasterCacheImages(checkerboardRasterCacheImages);
       builder.setCheckerboardOffscreenLayers(checkerboardOffscreenLayers);
  
positive.code: 
    @override
    ui.EngineLayer addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) {
      final Rect shiftedRect = rect.shift(layerOffset);
      builder.addPlatformView(
        viewId,
        offset: shiftedRect.topLeft,
  
negative.code: 
    @override
    ui.EngineLayer addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) {
      final Rect shiftedRect = layerOffset == Offset.zero ? rect : rect.shift(layerOffset);
      builder.addTexture(
        textureId,
        offset: shiftedRect.topLeft,
  