Expand <details> for find-in-page and element fragments

source

@@ -75340,6 +75340,17 @@ body { display:none }
   can navigate through the <span data-x="fip-matches">matches</span> by advancing the <span
   data-x="fip-active-match">active match</span> using the <span>find-in-page interface</span>.</p>
 
+  <p>When a find-in-page search begins, all <code>details</code> elements in the page which are not
+  <code data-x="attr-details-open">open</code> should be rendered as if they were open so that
+  find-in-page can look for matches inside of them, but without modifying the <code
+  data-x="attr-details-open">open</code> attribute. After the find-in-page search is done, the
+  closed details elements should go back to not being rendered.
+
+  When find-in-page chooses a new <span data-x="fip-active-match">active match</span>, all
+  <code>details</code> elements in the flat tree ancestor chain of the <span
+  data-x="fip-active-match">active match</span> must be opened if the are not already open before
+  the <span data-x="fip-active-match">active match</span> is scrolled into view.
+
   <p class="XXX"><a href="https://github.com/whatwg/html/issues/3539">Issue #3539</a> tracks
   standardizing how <span>find-in-page</span> underlies the currently-unspecified <code
   data-x="">window.find()</code> API.</p>
@@ -86015,6 +86026,11 @@ new PaymentRequest(&hellip;); // Allowed to use
      <li><p>Set the <code>Document</code>'s <span>target element</span> to
      <var>target</var>.</p></li>
 
+     <li><p>If there are one or more <code>details</code> elements in the ancestor chain of
+     <var>target</var> which are not <code data-x="attr-details-open">open</code>, then <code
+     data-x"attr-details-open">open</code> the <code>details</code> element(s) containing
+     <var>target</var>.
+
      <li><p><span data-x="scroll an element into view">Scroll <var>target</var> into view</span>,
      with <var>behavior</var> set to "auto", <var>block</var> set to "start", and <var>inline</var>
      set to "nearest". <ref spec=CSSOMVIEW></p></li>