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

Source/core/accessibility/AXMockObject.h

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 37 matching lines @@
 
     // Must be called when the parent object clears its children.
     virtual void detachFromParent() OVERRIDE { m_parent = 0; }
 
 private:
     virtual bool isMockObject() const OVERRIDE { return true; }
 
     virtual bool computeAccessibilityIsIgnored() const OVERRIDE;
 };
 
-inline AXMockObject* toAXMockObject(AXObject* object)
-{
-    ASSERT(!object || object->isMockObject());
-    return static_cast<AXMockObject*>(object);
-}
+DEFINE_AX_OBJECT_TYPE_CASTS(AXMockObject, isMockObject());
 
 } // namespace WebCore
 
 #endif // AXMockObject_h