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

Source/core/accessibility/AXScrollView.h

Index: Source/core/accessibility/AXScrollView.h
diff --git a/Source/core/accessibility/AXScrollView.h b/Source/core/accessibility/AXScrollView.h
index e892a492566548df2117e3b63cf68ba9d18717f5..cf7e291024e41d7d34f14fba1cf068b327e37625 100644
--- a/Source/core/accessibility/AXScrollView.h
+++ b/Source/core/accessibility/AXScrollView.h
@@ -81,14 +81,7 @@ private:
     bool m_childrenDirty;
 };
 
-inline AXScrollView* toAXScrollView(AXObject* object)
-{
-    ASSERT(!object || object->isAXScrollView());
-    if (!object->isAXScrollView())
-        return 0;
-
-    return static_cast<AXScrollView*>(object);
-}
+DEFINE_AX_OBJECT_TYPE_CASTS(AXScrollView, isAXScrollView());
 
 } // namespace WebCore