Added some text to monky-patch the envent loop part from the HTML spec.

cssom-view-1/Overview.bs

@@ -1946,7 +1946,11 @@ Issue: In what order are scrollend events dispatched? Ordered based on scroll st
 
 This section integrates with the <a for=/>event loop</a> defined in HTML. [[!HTML]]
 
-When asked to <dfn export for=Document>run the move steps</dfn> for a {{Document}} <var>doc</var>, run these steps:
+When <a for=/>updating the rendering</a>, after running the scroll steps:
+
+1. For each fully active Document in docs, <dfn export for=Document>run the move steps</dfn> for that Document.
+
+When asked to <a>run the move steps</a> for a {{Document}} <var>doc</var>, run these steps:
 
 1. If <var>doc</var>'s client window has had its position relative to the <a>Web-exposed screen area</a> changed
     (e.g. as a result of the user moving the browser window)