Add the :open pseudo-class

source

@@ -74232,6 +74232,43 @@ Demos:
    <dd><p>The <code data-x="selector-volume-locked">:volume-locked</code> <span>pseudo-class</span>
    must match all <span data-x="media element">media elements</span> when the user agent's
    <span>volume locked</span> is true.</p></dd>
+
+   <dt><dfn selector><code data-x="selector-open">:open</code></dfn></dt>
+   <dd>
+    <p>An <code>Element</code> matches the <code data-x="selector-open">:open</code>
+    <span>pseudo-class</span> if it matches one of the following:</p>
+
+    <ol>
+     <li><p>A <code>details</code> element which has the <code
+     data-x="attr-details-open">open</code> attribute.</p></li>
+
+     <li><p>A <code>dialog</code> element which has the <code data-x="attr-dialog-open">open</code>
+     attribute.</p></li>
+
+     <li><p>A <code>select</code> element which is a <span>drop-down box</span> whose drop-down box
+     is open.</p></li>
+    </ol>
+   </dd>
+
+   <dt><dfn selector><code data-x="selector-closed">:closed</code></dfn></dt>
+   <dd>
+    <p>An <code>Element</code> matches the <code data-x="selector-closed">:closed</code>
+    <span>pseudo-class</span> if it matches one of the following:</p>
+
+    <p>An <code>Element</code> <var>element</var> <dfn>matches the closed selector</dfn> that matches
+    one of the following:</p>
+
+    <ol>
+     <li><p>A <code>details</code> element which does not have the <code
+     data-x="attr-details-open">open</code> attribute.</p></li>
+
+     <li><p>A <code>dialog</code> element which does not have the <code
+     data-x="attr-dialog-open">open</code> attribute.</p></li>
+
+     <li><p>A <code>select</code> element which is a <span>drop-down box</span> whose drop-down box
+     is closed.</p></li>
+    </ol>
+   </dd>
   </dl>
 
   <p class="note">This specification does not define when an element matches the <code undefined