Disable PageSwapEvent's activation on cross-origin redirects

Closes whatwg#10196.

source

@@ -102459,9 +102459,20 @@ location.href = '#foo';</code></pre>
    <li><p>Let <var>activation</var> be null.</p></li>
 
    <li>
-    <p>If <var>targetEntry</var>'s <span data-x="she-document">document</span>'s <span
-    data-x="concept-document-origin">origin</span> is <span>same origin</span> with
-    <var>displayedDocument</var>'s <span data-x="concept-document-origin">origin</span>, then:
+    <p>If all of the following are true:</p>
+
+    <ul>
+     <li><p><var>targetEntry</var>'s <span data-x="she-document">document</span>'s <span
+     data-x="concept-document-origin">origin</span> is <span>same origin</span> with
+     <var>displayedDocument</var>'s <span data-x="concept-document-origin">origin</span>;
+     and</p></li>
+
+     <li><p><var>targetEntry</var>'s <span data-x="she-document">document</span>'s
+     <span>was created via cross-origin redirects</span> is false, or <var>targetEntry</var>'s
+     <span data-x="she-document">document</span>'s <span>latest entry</span> is not null,</p></li>
+    </ul>
+
+    <p>then:</p>
 
     <ol>
      <li>
@@ -102503,6 +102514,11 @@ location.href = '#foo';</code></pre>
       </dl>
      </li>
     </ol>
+
+    <p class="note">This means that a cross-origin redirect during a navigation would result in a
+    null <code data-x="dom-PageSwapEvent-activation">activation</code> in the old document's
+    <code>PageSwapEvent</code>, unless the new document is being restored from <a
+    href="#note-bfcache">bfcache</a>.</p>
    </li>
 
    <li><p><span data-x="concept-event-fire">Fire an event</span> named