Running mozregression with the `layout.css.page-size.enabled` pref manually enabled (to avoid bisecting to the pref-default-enabling commit), I got this regression range: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=61b00062dcdd41077516b098afe63fd49ba44187&tochange=4aee63294f3940bf9b80611a4e6989700a558386 (And in "good" builds before that, it looks like we're just ignoring the specified page size, basically.)
Bug 1763246 Comment 3 Edit History
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Running mozregression with the `layout.css.page-size.enabled` pref manually enabled (to avoid bisecting to the pref-default-enabling commit), I got this regression range: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=61b00062dcdd41077516b098afe63fd49ba44187&tochange=4aee63294f3940bf9b80611a4e6989700a558386 ...which is just bug 1647851. (In "good" builds before that, it looks like we're just ignoring the specified page size, basically, which trivially prevents the clipping issue.)