Created attachment 707183 [details] [diff] [review] Patch v1 http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=2073 shows that IE/Chrome/Opera don't support it.
Comment on attachment 707183 [details] [diff] [review] Patch v1 r=dbaron. If you land after bug 835169, please remove the outer if, though.
Will do. Thanks.
Yoshino-san updated: https://developer.mozilla.org/en-US/docs/Site_Compatibility_for_Firefox_21 As it wasn't documented elsewhere, and it was non-standard and quite cryptic, I don't think we need more doc. Switch back to dev-doc-needed if you disagree.