Do not unload during same-document history step application

Closes #9819.

source

@@ -100521,14 +100521,21 @@ location.href = '#foo';</code></pre>
         data-x="changing-nav-continuation-update-only">update-only</span> is false, then:</p>
 
         <ol>
-         <li><p><span data-x="unload a document">Unload</span> <var>displayedDocument</var> given
-         <var>targetEntry</var>'s <span data-x="she-document">document</span>.</p></li>
-
-         <li><p>For each <var>childNavigable</var> of <var>displayedDocument</var>'s
-         <span>descendant navigables</span>, <span>queue a global task</span> on the
-         <span>navigation and traversal task source</span> given <var>childNavigable</var>'s <span
-         data-x="nav-window">active window</span> to <span data-x="unload a document">unload</span>
-         <var>childNavigable</var>'s <span data-x="nav-document">active document</span>.</p></li>
+         <li>
+          <p>If <var>targetEntry</var>'s <span data-x="she-document">document</span> does not equal
+          <var>displayedDocument</var>, then:</p>
+
+          <ol>
+           <li><p><span data-x="unload a document">Unload</span> <var>displayedDocument</var> given
+           <var>targetEntry</var>'s <span data-x="she-document">document</span>.</p></li>
+
+           <li><p>For each <var>childNavigable</var> of <var>displayedDocument</var>'s
+           <span>descendant navigables</span>, <span>queue a global task</span> on the
+           <span>navigation and traversal task source</span> given <var>childNavigable</var>'s
+           <span data-x="nav-window">active window</span> to <span data-x="unload a
+           document">unload</span> <var>childNavigable</var>'s <span data-x="nav-document">active
+           document</span>.</p></li>
+          </ol>
 
          <li><p><span>Activate history entry</span> <var>targetEntry</var> for
          <var>navigable</var>.</p></li>