[css-scrollbars] Update test coverage

Author: frivoal

css-scrollbars-1/Overview.bs

@@ -57,6 +57,10 @@ Scope</h3>
 		without affecting other aspects of scrollability.
 	</ol>
 
+	<wpt title="Tests that related to the specification as a whole, without exerting any specific part">
+		invalid-needs-layout-crash.html
+	</wpt>
+
 <h4 id="out-of-scope">
 Out Of Scope</h4>