In case the logic visible area is known, info is provided only about the
visible headers. Given that only relative sizes (no absolute positions)
are provided, a placeholder row/col is added to the result that contains
the total size of the skipped items.

These placeholder items are not needed when providing all headers, so
don't emit them.

Change-Id: I48ccb73554313f4d2bb420e4402995719b0f9f7d