Introduce DEFINE_INLINE_BOX_TYPE_CASTS, and use it

Source/core/rendering/InlineTextBox.h

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 172 matching lines @@
     void paintDocumentMarker(GraphicsContext*, const FloatPoint& boxOrigin, DocumentMarker*, RenderStyle*, const Font&, bool grammar);
     void paintTextMatchMarker(GraphicsContext*, const FloatPoint& boxOrigin, DocumentMarker*, RenderStyle*, const Font&);
 
     TextRun::ExpansionBehavior expansionBehavior() const
     {
         return (canHaveLeadingExpansion() ? TextRun::AllowLeadingExpansion : TextRun::ForbidLeadingExpansion)
             | (expansion() && nextLeafChild() ? TextRun::AllowTrailingExpansion : TextRun::ForbidTrailingExpansion);
     }
 };
 
-inline InlineTextBox* toInlineTextBox(InlineBox* inlineBox)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!inlineBox || inlineBox->isInlineTextBox());
-    return static_cast<InlineTextBox*>(inlineBox);
-}
-
-inline const InlineTextBox* toInlineTextBox(const InlineBox* inlineBox)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!inlineBox || inlineBox->isInlineTextBox());
-    return static_cast<const InlineTextBox*>(inlineBox);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toInlineTextBox(const InlineTextBox*);
+DEFINE_INLINE_BOX_TYPE_CASTS(InlineTextBox);
 
 inline RenderText* InlineTextBox::textRenderer() const
 {
     return toRenderText(renderer());
 }
 
 void alignSelectionRectToDevicePixels(FloatRect&);
 
 } // namespace WebCore
 
 #endif // InlineTextBox_h