In a matched rule, find a long enough property, something like
font-family: dejavu sans mono, monospace;
Start gradually changing the sidebar width until the property no longer fits the sidebar and starts wrapping onto the next line.
At this point the property text indent will get lost, the former starting just at the left sidebar boundary.
Created attachment 195503 [details]
Comment on attachment 195503 [details]
Clearing flags on attachment: 195503
Committed r147088: <http://trac.webkit.org/changeset/147088>
All reviewed patches have been landed. Closing bug.