mobile - show-user-location
1. if canvas-based layers are in use, don't draw the hack range marker (as any leaflet path-based drawing is slow, and they don't support SVG styles)
2. only add/remove the circle marker layer when needed - as the leaflet library doesn't document what will happen if a removed layer is removed again, or an added layer is added again
render queue: when using canvas-based L.Path-s, it's most efficient to draw as much as possible every time - so quick-n-dirty change to the batch limits
with canvas based L.Paths, it's inefficient to draw too frequently, so reduce the debug tile refresh rate even further