Flutter's web engine drops every built path at the end of a frame, so a
path made of lineTo calls is rebuilt point by point, one call into
CanvasKit each, every frame it is drawn. The map's playable-area clip
has thousands of points, which cost about 3 ms a frame while a cone was
dragged. addPolygon hands each ring over in one call; the shape is the
same, and screenshots of all four test maps match main pixel for pixel.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>