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.
We were incorrectly looking at the CSS computed values for width and
height to determine the natural size of <svg> root elements.
This meant that elements where the attribute and computed value were
different values would end up with incorrect natural size.
