https://bugzilla.mozilla.org/show_bug.cgi?id=1358018
We change dom/webidl/CSSStyleSheet.webidl plus dom/interfaces/css/nsIDOMCSSGroupingRule.idl and dom/interfaces/css/nsIDOMCSSStyleSheet.idl (the latter just make [optional]; the former make optional unsigned long index = 0).
https://bugzilla.mozilla.org/show_bug.cgi?id=1358018
We change
dom/webidl/CSSStyleSheet.webidlplusdom/interfaces/css/nsIDOMCSSGroupingRule.idlanddom/interfaces/css/nsIDOMCSSStyleSheet.idl(the latter just make[optional]; the former makeoptional unsigned long index = 0).