merge_pr_46347

Use normalize-newlines algorithm for setCustomValidity

This is for whatwg/html#10350

Differential Revision: https://phabricator.services.mozilla.com/D210688

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1896923
gecko-commit: c9931f28fd168fb6f179eecf28a87a1a738fde0d
gecko-reviewers: emilio