[css3-animations] Interaction of animation-fill-mode with running/completed animations

Assuming a simple animation such as:

	#menu {
      	animation: slide 2s;
	}

	@keyframes slide-right {
      	from { left: 100px; }
	      to { left: 600px; }
	}

a. What happens if script sets animation-fill-mode on #menu to forwards during the animation? 
b. What happens if script sets animation-fill-mode on #menu after the animation has completed?

The current draft [1] does not say; I assume a. is covered by the snapshot clause [2]: 

# The values used for the keyframes and animation properties are snapshotted at 
# the time the animation starts. Changing them during the execution of the animation 
# has no effect.

I would expect b. to have no effect until a new animation is started on #menu.






[1] http://dev.w3.org/csswg/css3-animations/
[2] http://dev.w3.org/csswg/css3-animations/#animations