[4] 色々なところで参照されています。
[1] Rename non-relative to cannot-be-a-base-URL · whatwg/url@2f4161d ( 版) <https://github.com/whatwg/url/commit/2f4161d9f82b1752d9627ee7f34886e94464b054>
[2] Editorial: non-relative flag got renamed · whatwg/html@d360c27 ( 版) <https://github.com/whatwg/html/commit/d360c27d44c52390441b5910d39e898160ec016d>
[3] Update for URL's cannot-be-a-base-URL flag (annevk著, ) <https://github.com/whatwg/fetch/commit/1f0b7ead88a0535f9ff1135e94dac3d2b031d8af>