From what I can tell, that's
ZoneAbilityFrame and it's attached to
ExtraAbilityContainer. The position is managed by
UIParent.
Code:
["ExtraAbilityContainer"] = {baseY = true, yOffset = 0, bottomEither = actionBarOffset, overrideActionBar = overrideActionBarTop, petBattleFrame = petBattleTop, bonusActionBar = 1, pet = 1, watchBar = 1, tutorialAlert = 1, powerBarWidgets = 1};
FrameXML\UIParent.lua:2482