Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXSpinButton.h

Index: Source/modules/accessibility/AXSpinButton.h
diff --git a/Source/modules/accessibility/AXSpinButton.h b/Source/modules/accessibility/AXSpinButton.h
index ce0a53694a7ef5115ffdc6bab5e848c76a7512bd..554ae7223ecf3018d3b81248d3642a4b75b0d7ea 100644
--- a/Source/modules/accessibility/AXSpinButton.h
+++ b/Source/modules/accessibility/AXSpinButton.h
@@ -36,14 +36,14 @@ class AXObjectCacheImpl;
 
 class AXSpinButton final : public AXMockObject {
 public:
-    static PassRefPtr<AXSpinButton> create(AXObjectCacheImpl*);
+    static PassRefPtr<AXSpinButton> create(AXObjectCacheImpl&);
     virtual ~AXSpinButton();
 
     void setSpinButtonElement(SpinButtonElement* spinButton) { m_spinButtonElement = spinButton; }
     void step(int amount);
 
 private:
-    explicit AXSpinButton(AXObjectCacheImpl*);
+    explicit AXSpinButton(AXObjectCacheImpl&);
 
     virtual AccessibilityRole roleValue() const override;
     virtual bool isSpinButton() const override { return true; }
@@ -58,14 +58,14 @@ private:
 
 class AXSpinButtonPart final : public AXMockObject {
 public:
-    static PassRefPtr<AXSpinButtonPart> create(AXObjectCacheImpl*);
+    static PassRefPtr<AXSpinButtonPart> create(AXObjectCacheImpl&);
     virtual ~AXSpinButtonPart() { }
 
     bool isIncrementor() const { return m_isIncrementor; }
     void setIsIncrementor(bool value) { m_isIncrementor = value; }
 
 private:
-    explicit AXSpinButtonPart(AXObjectCacheImpl*);
+    explicit AXSpinButtonPart(AXObjectCacheImpl&);
     bool m_isIncrementor : 1;
 
     virtual bool press() const override;