If you try to identify an element with mulitple CSS plus selectors it is not working, if the first selector is a input[type="checkbox"]:checked.
This bug is also there for input[type="radiao]:checked, but e.g for div:hover it is working.
There is a minimal testcase her : http://www.basechat.com/chromebug/checkbox.htm
You can check and uncheck the checkbox to generate the bug, and test in firefox or IE to see the expected behavior.
This is the thing not working: "input[type="checkbox"]:checked + div + div"
Created attachment 245852 [details]
Comment on attachment 245852 [details]
Clearing flags on attachment: 245852
Committed r179484: <http://trac.webkit.org/changeset/179484>
All reviewed patches have been landed. Closing bug.