Sets the scroll child for the scroll frame. The scroll child frame represents the (generally larger) area into which the scroll frame provides a (generally smaller) movable "window". The child must have an absolute size, set either by <AbsDimension> in XML or using both SetWidth() and SetHeight() in Lua.

Setting a frame's scroll child involves changing the child frame's parent -- thus, if the frame's scroll child is protected, this operation cannot be performed while in combat.