Cleanup <static_cast>: Switch to toFoo for Accessibility Objects.

Source/core/accessibility/AccessibilityScrollbar.h

 /*
  * Copyright (C) 2010 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 46 matching lines @@
 
     virtual bool isEnabled() const OVERRIDE;
 
     // Assumes float [0..1]
     virtual void setValue(float) OVERRIDE;
     virtual float valueForRange() const OVERRIDE;
 
     RefPtr<Scrollbar> m_scrollbar;
 };
 
+inline AccessibilityScrollbar* toAccessibilityScrollbar(AccessibilityObject* object)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isAccessibilityScrollbar());
+    return static_cast<AccessibilityScrollbar*>(object);
+}
+
+inline const AccessibilityScrollbar* toAccessibilityScrollbar(const AccessibilityObject* object)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isAccessibilityScrollbar());
+    return static_cast<const AccessibilityScrollbar*>(object);
+}
+
+// This will catch anyone doing an unnecessary cast.
+void toAccessibilityScrollbar(const AccessibilityScrollbar*);
+
 } // namespace WebCore
 
 #endif // AccessibilityScrollbar_h