Implement the inert attribute

third_party/WebKit/Source/modules/accessibility/AXMenuListOption.cpp

Index: third_party/WebKit/Source/modules/accessibility/AXMenuListOption.cpp
diff --git a/third_party/WebKit/Source/modules/accessibility/AXMenuListOption.cpp b/third_party/WebKit/Source/modules/accessibility/AXMenuListOption.cpp
index a4353de322f57ae95c800afa59aca59869ecfffd..af8b879f8aa95cb684c00df08472d6ac07eb7339 100644
--- a/third_party/WebKit/Source/modules/accessibility/AXMenuListOption.cpp
+++ b/third_party/WebKit/Source/modules/accessibility/AXMenuListOption.cpp
@@ -64,6 +64,26 @@ Element* AXMenuListOption::ActionElement() const {
   return element_;
 }
 
+AXObjectImpl* AXMenuListOption::ComputeParent() const {
+  Node* node = GetNode();
+  if (!node)
+    return nullptr;
+  HTMLSelectElement* select = toHTMLOptionElement(node)->OwnerSelectElement();
+  if (!select)
+    return nullptr;
+  AXObjectImpl* select_ax_object = AxObjectCache().GetOrCreate(select);
+  if (select_ax_object->HasChildren()) {
+    const auto& child_objects = select_ax_object->Children();
+    DCHECK(!child_objects.IsEmpty());
+    DCHECK_EQ(child_objects.size(), 1UL);
+    DCHECK(child_objects[0]->IsMenuListPopup());
+    ToAXMenuListPopup(child_objects[0].Get())->UpdateChildrenIfNecessary();
+  } else {
+    select_ax_object->UpdateChildrenIfNecessary();
+  }
+  return parent_.Get();
+}
+
 bool AXMenuListOption::IsEnabled() const {
   // isDisabledFormControl() returns true if the parent <select> element is
   // disabled, which we don't want.