Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXMenuList.h

Index: Source/modules/accessibility/AXMenuList.h
diff --git a/Source/modules/accessibility/AXMenuList.h b/Source/modules/accessibility/AXMenuList.h
index 0f0a2af6e5219490360aca5621d7f64d253b2bd0..b4650e758fca5f92768b3a79f1e9e7f7a1635343 100644
--- a/Source/modules/accessibility/AXMenuList.h
+++ b/Source/modules/accessibility/AXMenuList.h
@@ -35,7 +35,7 @@ class LayoutMenuList;
 
 class AXMenuList final : public AXLayoutObject {
 public:
-    static PassRefPtr<AXMenuList> create(LayoutMenuList* layoutObject, AXObjectCacheImpl*);
+    static PassRefPtr<AXMenuList> create(LayoutMenuList* layoutObject, AXObjectCacheImpl&);
 
     virtual bool isCollapsed() const override;
     virtual AccessibilityExpanded isExpanded() const override final;
@@ -47,7 +47,7 @@ public:
     void didHidePopup();
 
 private:
-    AXMenuList(LayoutMenuList*, AXObjectCacheImpl*);
+    AXMenuList(LayoutMenuList*, AXObjectCacheImpl&);
 
     virtual bool isMenuList() const override { return true; }
     virtual AccessibilityRole determineAccessibilityRole() override final;