[css-conditional] Allow parens to be dropped from single-argument supports() method calls per WG resolution. <https://lists.w3.org/Archives/Public/www-style/2015Aug/0051.html>

Author: fantasai

css-conditional/Overview.bs

@@ -1025,7 +1025,8 @@ partial interface CSS {
     <p>
       When invoked with a single <var>conditionText</var> argument,
       it must return <code>true</code> if <var>conditionText</var>,
-      when parsed and evaluated as a <code>supports_condition</code>,
+      when either parsed and evaluated as a <code>supports_condition</code>
+      or parsed as a <code>declaration</code>, wrapped in implied parentheses, and evaluated as a <code>supports_condition</code>,
       would return true.
       Otherwise, it must return <code>false</code>.
   </dl>
@@ -1037,6 +1038,9 @@ Changes</h2>
 <a href="https://www.w3.org/TR/2013/CR-css3-conditional-20130404/">4 April 2013 Candidate Recommendation</a>:
 
 <ul>
+  <li>Allow the <code title=''>supports()</code> method
+      to imply parentheses for simple declarations,
+      for consistency with the ''@import'' rule’s ''supports()'' function.
   <li>Fixed missing semicolons in IDL code.
   <li>Updated links, terminology, and example code in response to changes to other modules.
 </ul>