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 9676ad9ddce2b7ee4894c6e2e4d40f6a32c96037..8b236d6e79f76916765b029c0c58fa3536aa20f8 100644
--- a/third_party/WebKit/Source/modules/accessibility/AXMenuListOption.cpp
+++ b/third_party/WebKit/Source/modules/accessibility/AXMenuListOption.cpp
@@ -27,6 +27,7 @@
 
 #include "SkMatrix44.h"
 #include "core/dom/AccessibleNode.h"
+#include "core/html/HTMLSelectElement.h"
 #include "modules/accessibility/AXMenuListPopup.h"
 #include "modules/accessibility/AXObjectCacheImpl.h"
 
@@ -63,6 +64,26 @@ Element* AXMenuListOption::ActionElement() const {
   return element_;
 }
 
+AXObject* AXMenuListOption::ComputeParent() const {
+  Node* node = GetNode();
+  if (!node)
+    return nullptr;
+  HTMLSelectElement* select = toHTMLOptionElement(node)->OwnerSelectElement();
+  if (!select)
+    return nullptr;
+  AXObject* 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.