Define the :placeholder-shown pseudo-class for HTML elements

https://drafts.csswg.org/selectors/#placeholder

PR: #1354

source

@@ -67700,6 +67700,30 @@ Demos:
    </dd>
 
 
+   <dt><dfn data-noexport=""><code
+   data-x="selector-placeholder-shown">:placeholder-shown</code></dfn></dt>
+
+   <dd>
+
+    <p>The <code data-x="selector-placeholder-shown">:placeholder-shown</code>
+    <span>pseudo-class</span> must match any element falling into one of the following
+    categories:</p>
+
+    <ul>
+
+     <li><code>input</code> elements that have a <code
+     data-x="attr-input-placeholder">placeholder</code> attribute whose value is currently being
+     presented to the user.</li>
+
+     <li><code>textarea</code> elements that have a <code
+     data-x="attr-textarea-placeholder">placeholder</code> attribute whose value is currently being
+     presented to the user.</li>
+
+    </ul>
+
+   </dd>
+
+
    <dt><dfn data-noexport=""><code data-x="selector-valid">:valid</code></dfn></dt>
 
    <dd>