[cssom-view-1] note about visual viewport scroll and scrollend

Author: Adam Argyle

cssom-view-1/Overview.bs

@@ -361,6 +361,8 @@ the following steps must be run:
   Otherwise, perform an <a>instant scroll</a> of <var>box</var> to <var>position</var>. After an <a>instant scroll</a> emit the <a event>scrollend</a> event.
 
   Note: If the scroll position did not change as a result of the user interaction or programmatic invocation, where no translations were applied as a result, then no <a event>scrollend</a> event fires because no scrolling occured.
+
+  Note: In the case the VisualViewport was scrolled, yielding no translation changes in the document, emit the <a event>scrollend</a> on the VisualViewport just as the <a event>scroll</a> event is emitted for VisualViewport scrolling.
 </ol>
 
 Scroll is <dfn lt="scroll completed">completed</dfn> when the scroll position has no more pending updates or translations and the user has completed their gesture. Scroll position updates include smooth or instant mouse wheel scrolling, keyboard scrolling, scroll-snap events, or other APIs and gestures which cause the scroll position to update and possibly interpolate. User gestures like touch panning or trackpad scrolling aren't complete until pointers or keys have released.