Properly enable letterboxing (again)
It seems while rebasing in legacy/trac#30429 (moved) we did not realize that the letterboxing patches made it into ESR 68 yet the pref to enabled the functionality needs still to get set.
It seems while rebasing in legacy/trac#30429 (moved) we did not realize that the letterboxing patches made it into ESR 68 yet the pref to enabled the functionality needs still to get set.