link to use-cases, why not pseudos per issue #2009

Author: tantek

css-scrollbars-1/Overview.bs

@@ -21,11 +21,18 @@ Introduction</h2>
 Scope</h3>
 <em>This subsection is non-normative.</em>
 
-This module adds color properties for styling the scrollbar (if any) of an element as has been increasingly adopted 
-on the web since Windows IE 5.5 introduced it in 2000. [add citations of examples from Bugzilla 77790 and webcompat].
+This module adds color properties for styling the scrollbar (if any) of an element per 
+<a href="https://www.w3.org/wiki/Css-scrollbars#Use-cases">documented use-cases</a>,
+and as has been increasingly adopted 
+on the web since Windows IE 5.5 introduced it in 2000.
+[Note: Add citations of examples from Bugzilla 77790 and webcompat].
 
 Should we add scrollbar width? (<a href="https://github.com/w3c/csswg-drafts/issues/1958">Issue 1958</a>)
 
+Out of scope: 
+<a href="https://www.w3.org/wiki/Css-scrollbars#Why_not_pseudos">pseudo-elements for selecting specific parts of a scrollbar are unnecesssary</a>
+for the documented use-cases and are thus out of scope for this specification.
+
 <h3 id="values">
 Values</h3>