public void RemoveClocks(IEnumerable <AnimationTimelineClock> newClocks, AnimationLayerKey key)
        {
            AnimationLayer animationLayer = GetAnimationLayer(key);

            animationLayer.RemoveClocks(newClocks);

            if (key != AnimationLayerKey.Default && animationLayer.IsEmpty)
            {
                RemoveAnimationLayer(key);
            }

            LayerInvalidated.Raise(this);
        }