1 files changed, 39 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/semantics/forms/the-fieldset-element/disabled-003.html b/testing/web-platform/tests/html/semantics/forms/the-fieldset-element/disabled-003.html
new file mode 100644
index 0000000000..de01eb57fc
--- /dev/null
+++ b/testing/web-platform/tests/html/semantics/forms/the-fieldset-element/disabled-003.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Disable nested fieldsets with focused element</title>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/#the-fieldset-element">
+<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1427047">
+<link rel="author" href="mailto:xiaochengh@chromium.org">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+
+<div id=container1>
+  <fieldset id=target1>
+    <legend>foo</legend>
+    <fieldset>
+      <legend>bar</legend>
+      <input id=input1>
+    </fieldset>
+  </fieldset>
+</div>
+<script>
+test(() => {
+  input1.focus();
+  target1.disabled = true;
+  assert_not_equals(document.activeElement, input1);
+}, 'Disable light-nested fieldsets should not crash');
+</script>
+
+<div id=container2></div>
+<script>
+test(() => {
+  let n = 100;
+  let markup = '<fieldset><legend>foo</legend>'.repeat(n) +
+               '<input id=input2>' + '</fieldset>'.repeat(n);
+  container2.innerHTML = markup;
+  input2.focus();
+  container2.firstChild.disabled = true;
+  assert_not_equals(document.activeElement, input2);
+}, 'Disable deep-nested fieldsets should not hang');
+</script>
+