[css-contain-2] Replace the manual description of animation updates by waving at Animation/Transitions 2. Fixes w3c#5611.

Author: tabatkins

css-contain-2/Overview.bs

@@ -1660,28 +1660,19 @@ Restrictions and Clarifications {#cv-notes}
 
 	If script queries the style of a [=skipped=] element
 	(causing a [=style change event=])
-	such that knowing the state of animations is required
+	such that knowing the state of animations or transitions is required
 	to return correct information,
-	animations are "refreshed" at that moment
+	animation and transitions are sampled
 	according to the styles at the time of that [=style change event=]:
-	new animations are created if necessary;
-	existing animations are advanced
-	to the point on their timeline they would have been at
-	were they never skipped at all;
-	animations that have would have ended since the last "refresh"
-	are ended.
-
-	If a transition or animation-related event would have been triggered
-	as a result of changes occurring during the "refresh" interval,
-	they are fired when the animations are "refreshed",
-	in the same order they would have originally fired in
-	had the element never been [=skipped=].
-	If multiple iterations of an animation would have completed during this period,
-	only one {{animationiteration}} event must be triggered,
-	ordered as if it were triggered at the first completed iteration during the refresh interval.
+
+	[[css-animations-2#events]] and [[css-transitions-2#events]]
+	defines what objects are created
+	and what events are fired,
+	with what data,
+	when an animation or transition is updated,.
 
 	When an element stops being [=skipped=],
-	animations are refreshed
+	animations and transitions are sampled
 	and then resume advancing on their timelines as normal from that point.
 
 	Note: Overall, this is similar to the behavior of transitions/animations