WebKit export: [popover] Tabbing out of a popover causes a hang in ce…

…rtain cases (#50235)

https://bugs.webkit.org/show_bug.cgi?id=285811

html/semantics/popovers/popover-focus-2.html

@@ -173,3 +173,35 @@
   assert_equals(document.activeElement,otherElement,'focus does not move because it was not inside the popover');
 }, "Popover focus only returns to invoker when focus is within the popover");
 </script>
+
+<div id=no-focus-candidate>
+  <button popovertarget=no-focus-candidate-p tabindex="0">Toggle popover</button>
+  <div popover id=no-focus-candidate-p>
+    Popover with <button tabindex="0" popovertarget=no-focus-candidate-p2>focusable element</button>
+    <div popover id=no-focus-candidate-p2>Nested popover with <button tabindex="0">focusable element</button></div>
+  </div>
+</div>
+<script>
+promise_test(async t => {
+  const invoker = document.querySelector('#no-focus-candidate>button');
+  const popover = document.querySelector('#no-focus-candidate>[popover]');
+  const nestedPopover = document.querySelector('#no-focus-candidate>[popover]>[popover]');
+  invoker.focus(); // Make sure button is focused.
+  assert_equals(document.activeElement,invoker);
+  invoker.click(); // Activate the invoker
+  assert_true(popover.matches(':popover-open'), 'popover should be invoked by invoker');
+  assert_equals(document.activeElement,invoker, 'invoker should still be focused');
+  await sendTab();
+  assert_equals(document.activeElement,popover.querySelector('button'),'next up is the popover');
+  await sendEnter(); // Show nested popover
+  assert_true(nestedPopover.matches(':popover-open'), 'nested popover should be invoked by invoker');
+  await sendTab();
+  assert_equals(document.activeElement, nestedPopover.querySelector('button'), 'focus on the nested popover button');
+  popover.querySelector('button').disabled = true; // Make the invoker no longer a focus candidate.
+  await sendShiftTab();
+  assert_equals(document.activeElement, invoker, 'initial invoker should be focused, nested popover invoker is skipped since it is disabled');
+  nestedPopover.querySelector('button').focus();
+  await sendTab();
+  assert_equals(document.activeElement, document.body, 'no more focusable elements after the button');
+}, "Cases where the next focus candidate isn't in the direct parent scope");
+</script>