[1] Add history.index (domenic著, ) <https://github.com/whatwg/html/commit/f8e293fa081b29676405507b998ff2cbd9f41e42>
[7] Expose `history.index` in addition to `history.length` · Issue #2710 · whatwg/html () <https://github.com/whatwg/html/issues/2710>
[8] Add history.index by domenic · Pull Request #2944 · whatwg/html () <https://github.com/whatwg/html/pull/2944>
[9] Fix typo in previous commit (domenic著, ) <https://github.com/whatwg/html/commit/f8a212406c906bd72788cbea6ebd60f4bdb087a5>
[10] Fix typo in previous commit by domenic · Pull Request #2960 · whatwg/html () <https://github.com/whatwg/html/pull/2960>
[11] Remove history.index (domenic著, ) <https://github.com/whatwg/html/commit/430a6531dd6cb25c9fe7903c823e86eabfde784c>
[12] Remove history.index by domenic · Pull Request #3460 · whatwg/html () <https://github.com/whatwg/html/pull/3460>
[13] Session history indexing is broken · Issue #2985 · whatwg/html () <https://github.com/whatwg/html/issues/2985>