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

source

@@ -56988,6 +56988,27 @@ interface <dfn>HTMLDetailsElement</dfn> : <span>HTMLElement</span> {
  &lt;p>Direction: North&lt;/p>
 &lt;/details></code></pre>
 
+  <p>The <dfn>ancestor details revealing algorithm</dfn> is to run the following steps on
+  currentNode:</p>
+
+  <ol>
+   <li><p>While <var>currentNode</var> has a parent node, perform the following steps:</p></li>
+
+   <li><p>If <var>currentNode</var> is slotted into the second slot of a <code>details</code>
+   element:</p>
+
+     <ol>
+       <li><p>let <var>currentNode</var> be the <code>details</code> element which
+       <var>currentNode</var> is slotted into.</p></li>
+
+       <li><p>Add the <code data-x="attr-details-open">open</code> attribute to
+       <var>currentNode</var>.</p></li>
+     </ol>
+
+   <li><p>Otherwise, let <var>currentNode</var> be the parent node of
+   <var>currentNode</var>.</p></li>.
+  </ol>
+
   </div>
 
 
@@ -75340,6 +75361,25 @@ 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 find-in-page begins searching for matches, all <code>details</code> elements in the page
+  which are not <code data-x="attr-details-open">open</code> should have their second slot be added
+  to the rendering without modifying the <code data-x="attr-details-open">open</code> attribute.
+  After find-in-page finishes searching for matches, those details elements should have their second
+  slot be removed from the rendering again. This entire process must happen synchronously (and so is
+  not observable to users or to author code).</p>
+
+  <p>When find-in-page chooses a new <span data-x="fip-active-match">active match</span>, perform
+  the following steps:</p>
+
+  <ol>
+    <li><p>Let <var>node</var> be the first node in the <span data-x="fip-active-match">active
+    match</span>.</p></li>
+
+    <li><p><span>Queue a global task</span> on the <span>user interaction task source</span> given
+    <var>node</var>'s <span>relevant global object</span> to run the <span>ancestor details
+    revealing algorithm</span> on <var>node</var>.</p></li>
+  </ol>
+
   <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 +86055,8 @@ 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>Run the <span>ancestor details revealing algorithm</span> on <var>target</var>.</p></li>
+
      <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>