Replacing one BannerMessage notification with another causes incorrect CSS transition

[pfaffle]

The CSS transition which is meant to provide the "slide-out" behavior when you dismiss a BannerMessage notification has an unintended effect if you immediately replace it in the DOM with a different notification. If the notifications have different types (e.g. info, success), the color of the notification is transitioned instead.

Presumably the correct behavior is for the first notification to slide out and then the second will slide in?