[css-overflow-3] Mark 'overflow' on replaced elements at-risk. w3c#7435

Author: fantasai

css-overflow-3/Overview.bs

@@ -22,6 +22,7 @@ Abstract: This module contains the features of CSS relating to scrollable overfl
 Ignored Vars: B, P
 Ignored Terms: padding edge, viewport, line box, flex order, -webkit-box-orient
 At Risk: the 'max-lines' property
+At Risk: application of 'overflow' to [=replaced elements=]
 Status Text:
 	The description of 'overflow' and its longhands is considered
 	significantly more complete and correct than previous working drafts