Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXTableHeaderContainer.h

Index: Source/modules/accessibility/AXTableHeaderContainer.h
diff --git a/Source/modules/accessibility/AXTableHeaderContainer.h b/Source/modules/accessibility/AXTableHeaderContainer.h
index 63806740023420baa09fa2d78c0f752c8d466a8a..29966448de56079b2f438e5ad3b92e6f33364e54 100644
--- a/Source/modules/accessibility/AXTableHeaderContainer.h
+++ b/Source/modules/accessibility/AXTableHeaderContainer.h
@@ -39,10 +39,10 @@ class AXObjectCacheImpl;
 class AXTableHeaderContainer final : public AXMockObject {
 
 private:
-    explicit AXTableHeaderContainer(AXObjectCacheImpl*);
+    explicit AXTableHeaderContainer(AXObjectCacheImpl&);
 
 public:
-    static PassRefPtr<AXTableHeaderContainer> create(AXObjectCacheImpl*);
+    static PassRefPtr<AXTableHeaderContainer> create(AXObjectCacheImpl&);
     virtual ~AXTableHeaderContainer();
 
     virtual AccessibilityRole roleValue() const override { return TableHeaderContainerRole; }