Set iframe lazy load resumption steps to null on navigation

When an iframe element is navigated, the lazy-loading mechanism should not navigate it again.

Fixes #10213.

source

@@ -98718,6 +98718,14 @@ location.href = '#foo';</code></pre>
      https://github.com/whatwg/html/issues/1213
      https://software.hixie.ch/utilities/js/live-dom-viewer/?saved=1946 to 1955 -->
 
+   <li><p>Set <var>container</var> to <var>navigable</var>'s <span
+   data-x="nav-container">container</span>.</p></li>
+
+   <li><p>If <var>container</var> is an <code>iframe</code> element and <span>will lazy load
+   element steps</span> given <var>container</var> returns true, then <span>stop
+   intersection-observing a lazy loading element</span> <var>container</var> and set
+   <var>container</var>'s <span>lazy load resumption steps</span> to null.</p></li>
+
    <li id="navigate-convert-to-replace">
     <p>If <var>historyHandling</var> is "<code data-x="NavigationHistoryBehavior-auto">auto</code>",
     then:</p>