Update to relect HTML spec change

index.html

@@ -622,10 +622,10 @@ <h2>Creating a navigation timing entry</h2>
         <li>Set |document|'s <span>navigation timing entry</span> to |navigationTimingEntry|.
         <li>Set |navigationTimingEntry|'s <a data-for="PerformanceNavigationTiming">`Critical-CH` restart time</a>
         to |criticalCHRestart|.
-        <li>If document is the outermost main frame's document, set |navigationTimingEntry|'s
-        <a data-for="PerformanceNavigationTiming">not restored reasons</a> to the result of
-        creating a NotRestoredReasons object given |document|'s node navigable's active session
-        history entry's document state's not restored reasons and realm.</li>
+        <li>If |document|'s [=Document/not restored reasons=] is not null, then set
+        |navigationTimingEntry|'s [=PerformanceNavigationTiming/not restored reasons=] to the
+        result of [=creating a NotRestoredReasons object=] given |document|'s
+        [=Document/not restored reasons=].</li>
         <li>add |navigationTimingEntry| to |global|'s
         <a data-cite='performance-timeline-2#dfn-performance-entry-buffer'>performance entry buffer</a>.
       </ol>