Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXListBox.h

Index: Source/modules/accessibility/AXListBox.h
diff --git a/Source/modules/accessibility/AXListBox.h b/Source/modules/accessibility/AXListBox.h
index b6ee3760ea8905ddca192e824b4b64e7caa7629e..707f2faceff910556313643ba37dc7dc15a44995 100644
--- a/Source/modules/accessibility/AXListBox.h
+++ b/Source/modules/accessibility/AXListBox.h
@@ -38,10 +38,10 @@ class AXObjectCacheImpl;
 class AXListBox final : public AXLayoutObject {
 
 private:
-    AXListBox(LayoutObject*, AXObjectCacheImpl*);
+    AXListBox(LayoutObject*, AXObjectCacheImpl&);
 
 public:
-    static PassRefPtr<AXListBox> create(LayoutObject*, AXObjectCacheImpl*);
+    static PassRefPtr<AXListBox> create(LayoutObject*, AXObjectCacheImpl&);
     virtual ~AXListBox();
 
     virtual AccessibilityRole determineAccessibilityRole() override final;