@Xypherous What classifies as a "Drain"?

According to this link the new passives of and (and by extension, Windspeaker's Blessing) don't work on lifesteal and drain abilities. So I was curious as to what classified as a drain ability.

Are drains abilities those that deal damage and heal based on the damage dealt, such as Fiddle E, Warwick Q, and Yorick E? What about abilities that state that they "heal" regardless of damage in their description, such as Vlad ult/Q, Swain ult, and Renekton Q?