[2] allowfullscreen 属性の有無は、
parse a sandboxing directive 時の allow fullscreen flag
(入力) として用いられます。
[3] Make allowfullscreen and allowusermedia match implementations (annevk著, ) <https://github.com/whatwg/html/commit/9f6b91cb14a0f497ee5b3e7118ee65e687eaea78>
[4] Iframe sandboxing options for gUM · Issue #268 · w3c/mediacapture-main () <https://github.com/w3c/mediacapture-main/issues/268>
[5] Use HTML's new "allowed to use" algorithm (foolip著, ) <https://github.com/whatwg/fullscreen/commit/42f9d159f948865ac415f0ac6243ee0e0a5d2c1a>
[6] Integrate Feature Policy concepts into HTML (clelland著, ) <https://github.com/whatwg/html/commit/78741b7b5471ba213c68a22caff1a53c56d35ce8>
[7] Refer to feature policy spec (#107) (clelland著, ) <https://github.com/whatwg/fullscreen/commit/97ff618681926e3333e9a78208a994371ba59b59>
[8] Define fullscreen in terms of feature policy · Issue #106 · whatwg/fullscreen () <https://github.com/whatwg/fullscreen/issues/106>
[9] Refer to feature policy spec by clelland · Pull Request #107 · whatwg/fullscreen () <https://github.com/whatwg/fullscreen/pull/107>
sandboxを、 処理方法は parse a sandboxing directive を参照。