When an image has no intrinsic dimensions but has an intrinsic aspect
ratio, the CSS default sizing algorithm should resolve its size as a
contain constraint against the default object size. Previously, we
returned the default size directly, which caused such images to stretch
to fill the entire background positioning area. The SVG's default
`preserveAspectRatio` would then center the content within that
oversized viewport, making the image appear horizontally mispositioned.