There are some places in the animations code that call PostRestyleForAnimation when the reason they're doing that is to make the restyle code detect a difference in animation generation and produce an UpdateOpacityLayer or UpdateTransformLayer hint. I made PostResendToLayer in bug 847287 patch 5 to have a slightly more direct way to do this. I think some existing callers could use this as well.

Actually, I guess the only place I was thinking of is CommonAnimationManager::NotifyCollectionUpdated, and that can certainly be called when we actually need to update style, I think. (It's not at all specific to OMT Animations.) So I actually don't think there's anything to do here.