[5] HTML や xml-stylesheet 処理指令の media 属性は直接対応する
MediaList を持っていません。 (スタイル・シートを生成するものは
StyleSheet で間接的に存在しますが。)
[6] [cssom] Make MediaList.item return serialization. (upsuper著, ) <https://github.com/w3c/csswg-drafts/commit/33a023d4e9c0ad9c18f0becaf83ad8f20d0c3b56>
[7] [cssom] Why is CSSRuleList [LegacyArrayClass] · Issue #2601 · w3c/csswg-drafts () <https://github.com/w3c/csswg-drafts/issues/2601>
[8] [cssom] Remove [LegacyArrayClass] from CSSOM interfaces. (emilio著, ) <https://github.com/w3c/csswg-drafts/commit/b05eb1b9c05c22f771aff6a3ae7cdbb4a925522e>
[9] [cssom] Why is CSSRuleList [LegacyArrayClass] · Issue #2601 · w3c/csswg-drafts () <https://github.com/w3c/csswg-drafts/issues/2601>