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

Source/core/accessibility/AccessibilityTableColumn.h

 /*
  * Copyright (C) 2008 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 42 matching lines @@
 
     virtual void addChildren() OVERRIDE;
     virtual void setParent(AccessibilityObject*) OVERRIDE;
 
     virtual LayoutRect elementRect() const OVERRIDE;
 
 private:
     unsigned m_columnIndex;
     LayoutRect m_columnRect;
 
+    virtual bool isTableCol() const OVERRIDE { return true; }
     AccessibilityObject* headerObjectForSection(RenderTableSection*, bool thTagRequired);
     virtual bool computeAccessibilityIsIgnored() const OVERRIDE;
 };
 
+inline AccessibilityTableColumn* toAccessibilityTableColumn(AccessibilityObject* object)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isTableCol());
+    return static_cast<AccessibilityTableColumn*>(object);
+}
+
+inline const AccessibilityTableColumn* toAccessibilityTableColumn(const AccessibilityObject* object)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isTableCol());
+    return static_cast<const AccessibilityTableColumn*>(object);
+}
+
+// This will catch anyone doing an unnecessary cast.
+void toAccessibilityTableColumn(const AccessibilityTableColumn*);
+
 } // namespace WebCore
 
 #endif // AccessibilityTableColumn_h