[2] input 要素の files IDL属性は、
現在選択されているファイルを表す FileList を返します。
[3] [whatwg] Make files attribute of the input element writable ( ( 版)) <http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2012-May/036229.html>
[4] [whatwg] Make the files attribute of the input element writable ( ( 版)) <http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2013-January/038716.html>
[5] Web Applications 1.0 r8057 A typo fix in window.open(), and some internal comments for making input.files writable ( ( 版)) <http://html5.org/tools/web-apps-tracker?from=8056&to=8057>
[6] 22682 – forms: Make <input type=file>.files writable () <https://www.w3.org/Bugs/Public/show_bug.cgi?id=22682>
[7] Make <input type=file>.files settable (annevk著, ) <https://github.com/whatwg/html/commit/5dc7db2108656c9ce4b2dc7a8bb7dcde5c03afee>
[8] Make HTMLInputElement.prototype.files settable · Issue #2861 · whatwg/html () <https://github.com/whatwg/html/issues/2861>
[9] Make <input type=file>.files settable by annevk · Pull Request #2866 · whatwg/html () <https://github.com/whatwg/html/pull/2866>