Oilpan: Prepare moving AXObject to heap

Source/modules/accessibility/AXMenuListOption.h

Index: Source/modules/accessibility/AXMenuListOption.h
diff --git a/Source/modules/accessibility/AXMenuListOption.h b/Source/modules/accessibility/AXMenuListOption.h
index 92cf32d8bb7ff27863b3931e3aacef52fb4c182a..410a3a7d0fb5e58a068180e80b9d29a00f50be7f 100644
--- a/Source/modules/accessibility/AXMenuListOption.h
+++ b/Source/modules/accessibility/AXMenuListOption.h
@@ -35,10 +35,11 @@ class AXObjectCacheImpl;
 
 class AXMenuListOption final : public AXMockObject {
 public:
-    static PassRefPtr<AXMenuListOption> create(HTMLOptionElement* element, AXObjectCacheImpl& axObjectCache) { return adoptRef(new AXMenuListOption(element, axObjectCache)); }
+    static PassRefPtrWillBeRawPtr<AXMenuListOption> create(HTMLOptionElement* element, AXObjectCacheImpl& axObjectCache) { return adoptRefWillBeNoop(new AXMenuListOption(element, axObjectCache)); }
 
 private:
     explicit AXMenuListOption(HTMLOptionElement*, AXObjectCacheImpl&);
+    DECLARE_VIRTUAL_TRACE();
 
     virtual bool isMenuListOption() const override { return true; }
 
@@ -59,7 +60,7 @@ private:
     virtual String stringValue() const override;
     virtual bool computeAccessibilityIsIgnored(IgnoredReasons* = nullptr) const override;
 
-    HTMLOptionElement* m_element;
+    RawPtrWillBeWeakMember<HTMLOptionElement> m_element;
 };
 
 DEFINE_AX_OBJECT_TYPE_CASTS(AXMenuListOption, isMenuListOption());