Created attachment 346840 [details]
Given an animation definition with @keyframe rules containing transform: properties, and a :active selector which sets the animation-iteration-count to infinite, the animation will not stop when the :active state is removed. An identical animation which uses top: properties in its @keyframe will stop correctly.
Does this happen if you disable "Web Animations and CSS Integration"?
Actually, unless I misunderstand the test, it appears that Jer's test only works with the Web Animations code path and fails with the old code path.