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 previously crashing when invoking 'scroll to the fragment' on
such documents as it was unable to find the active document. This is
as a result of our AD-HOC implementation not setting up the document
fully to mark it is active before running the parser.
Fixes a crash on https://tweakers.net.
