Inline nodes in our layout tree have a position, so let's show it. By
centralizing the logic for this, block nodes now lose their redundant
'content-size' dump info which is already part of the box model dump.
Previously, `SVGSVGBox` would have a natural aspect ratio of 0 if it
had a viewbox with zero width. This led to a division by zero, causing
a crash.
Found by Domato.