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

Source/core/accessibility/AXSpinButton.h

Index: Source/core/accessibility/AXSpinButton.h
diff --git a/Source/core/accessibility/AXSpinButton.h b/Source/core/accessibility/AXSpinButton.h
index c118926c91e9ad367a6573ba066154b429c16f36..12ae3adb23b56b71ab141cad11759f122f1ef225 100644
--- a/Source/core/accessibility/AXSpinButton.h
+++ b/Source/core/accessibility/AXSpinButton.h
@@ -70,17 +70,8 @@ private:
     virtual LayoutRect elementRect() const OVERRIDE;
 };
 
-inline AXSpinButton* toAXSpinButton(AXObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isNativeSpinButton());
-    return static_cast<AXSpinButton*>(object);
-}
-
-inline AXSpinButtonPart* toAXSpinButtonPart(AXObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isSpinButtonPart());
-    return static_cast<AXSpinButtonPart*>(object);
-}
+DEFINE_AX_OBJECT_TYPE_CASTS(AXSpinButton, isNativeSpinButton());
+DEFINE_AX_OBJECT_TYPE_CASTS(AXSpinButtonPart, isSpinButtonPart());
 
 } // namespace WebCore