Add the :open pseudo-class

source

@@ -48169,6 +48169,11 @@ interface <dfn interface>HTMLInputElement</dfn> : <span>HTMLElement</span> {
   data-x="attr-input-type-checkbox">Checkbox</span> state) stop an <code>input</code> element from
   being <i data-x="concept-fe-mutable">mutable</i>.</p>
 
+  <p>Some states of the <code data-x="attr-input-type">type</code> attribute <dfn
+  data-x="input-support-picker">support a picker</dfn>, which is a popup that allows the user to
+  choose a value. Which states <span data-x="input-support-picker">support a picker</span> is up to
+  the user agent.</p>
+
   <p>The <span data-x="concept-node-clone-ext">cloning steps</span> for <code>input</code> elements
   must propagate the <span data-x="concept-fe-value">value</span>, <span
   data-x="concept-fe-dirty">dirty value flag</span>, <span
@@ -52636,8 +52641,10 @@ You cannot submit this form when the field is incorrect.</samp></pre>
    <dt><code data-x=""><var>input</var>.<span subdfn data-x="dom-input-showPicker">showPicker</span>()</code></dt>
 
    <dd>
-    <p>Shows any applicable picker UI for <var>input</var>, so that the user can select a value. (If
-    no picker UI is implemented for the given control, then this method does nothing.)</p>
+    <p>If <var>input</var> does not <span data-x="input-support-picker">support a picker</span>,
+    this method does nothing.</p>
+
+    <p>Shows any applicable picker UI for <var>input</var>, so that the user can select a value.</p>
 
     <p>Throws an <span>"<code>InvalidStateError</code>"</span> <code>DOMException</code> if
     <var>input</var> is not <span data-x="concept-fe-mutable">mutable</span>.</p>
@@ -53010,7 +53017,8 @@ You cannot submit this form when the field is incorrect.</samp></pre>
    <li>
     <p>Otherwise, the user agent should show any relevant user interface for selecting a value for
     <var>element</var>, in the way it normally would when the user interacts with the control. (If
-    no such UI applies to <var>element</var>, then this step does nothing.)</p>
+    <var>element</var> does not <span data-x="input-support-picker">support a picker</span>, then
+    this step does nothing.)</p>
 
     <p>If such a user interface is shown, it must respect the requirements stated in the relevant
     parts of the specification for how <var>element</var> behaves given its <code
@@ -74795,6 +74803,26 @@ 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>
+
+     <li><p>An <code>input</code> element which <span data-x="input-support-picker">supports a
+     picker</span> popup and whose picker popup is open.</p></li>
+    </ol>
+   </dd>
   </dl>
 
   <p class="note">This specification does not define when an element matches the <code undefined