[css-ui-4] maintains caret visibility despite transforms

Closes w3c#4784

Author: frivoal

css-ui-4/Overview.bs

@@ -1193,6 +1193,13 @@ If the edited text is laid out on a path,
 for instance by using the SVG <{textPath}> element,
 UAs should also account for this.
 
+The thickness of ''caret-shape/bar'' and ''caret-shape/underscore'' carets--
+as well as that of ''caret-shape/auto'' carets with a similar rendering--
+is determined by the user agent.
+When practical, the user agent should choose a thickness that ensures
+the caret remains visible even if it has been scaled down
+via means such as transformations [[CSS-TRANSFORMS-1]].
+
 The stacking position of the caret is left undefined within the following constraints:
 
 <ul>
@@ -2162,6 +2169,9 @@ the following normative changes have been made:
 		Restricted the applicability of ''appearance: button''
 		so that it can no longer give a buttony appearance
 		to widgets that aren't buttons to start with.
+
+	<li>
+		Add a clause to preserve visibility of carets even when scaled down via transforms.
 </ul>
 
 <h3 id=changes-22-12-2017 class=no-num>Changes from the