I bisected the problem to this range: http://trac.webkit.org/log/trunk/?rev=82003&stop_rev=81947, and it looks like 81992 is the most likely culprit, so I am calling it.
Reduction attached. Interesting combination:
1) strict mode
2) whitespace before label
3) select elements.
First reported in in http://code.google.com/p/chromium/issues/detail?id=78871.
Created attachment 88897 [details]
Per chromium bug report, this affects verizonwireless.com - payment page does not display the credit card expiration year.
Please put all relevant information in bugzilla when moving chromium bugs - there is no reason why everyone should click through to other bug tracking systems and hunt it down for themselves.
Created attachment 89245 [details]
Attachment 89245 [details] did not pass style-queue:
Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'LayoutTests/ChangeLog', u'LayoutTests/fast..." exit_code: 1
LayoutTests/ChangeLog:1: ChangeLog entry has no bug number [changelog/bugnumber] 
Total errors found: 1 in 6 files
If any of these errors are false positives, please file a bug against check-webkit-style.
Fixed in r83629.