Chrome 23 is out and people start to see the rulers when opening the Elements panel. Some people find it annoying and want to turn it off.
See the comment on https://plus.google.com/u/0/115203843155141445032/posts/ZYezofJmMya
Created attachment 172971 [details]
Committed r133885: <http://trac.webkit.org/changeset/133885>
It's more than just a mere annoyance... the ruler appears over elements near the top and right edges that are actively being inspected, thereby not only defeating the purpose of the ruler, but obstructing precise visual representations of margin and padding.