Introduce DEFINE_AX_OBJECT_TYPE_CASTS to replace manual toFoo() in accessibility child class

Source/core/accessibility/AXScrollbar.h

Index: Source/core/accessibility/AXScrollbar.h
diff --git a/Source/core/accessibility/AXScrollbar.h b/Source/core/accessibility/AXScrollbar.h
index 37fcdc8a383b7d489d3aa5767646ad62406ed494..42eaca23470d57f8c596f83f7c1177f002085d6d 100644
--- a/Source/core/accessibility/AXScrollbar.h
+++ b/Source/core/accessibility/AXScrollbar.h
@@ -64,20 +64,7 @@ private:
     RefPtr<Scrollbar> m_scrollbar;
 };
 
-inline AXScrollbar* toAXScrollbar(AXObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isAXScrollbar());
-    return static_cast<AXScrollbar*>(object);
-}
-
-inline const AXScrollbar* toAXScrollbar(const AXObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isAXScrollbar());
-    return static_cast<const AXScrollbar*>(object);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toAXScrollbar(const AXScrollbar*);
+DEFINE_AX_OBJECT_TYPE_CASTS(AXScrollbar, isAXScrollbar());
 
 } // namespace WebCore