Introduce DEFINE_RENDER_OBJECT_TYPE_CASTS to replace manual toRenderFoo, and use it

Source/core/rendering/RenderTextControlMultiLine.h

 /*
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2009 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 30 matching lines @@
     virtual float getAvgCharWidth(AtomicString family);
     virtual LayoutUnit preferredContentLogicalWidth(float charWidth) const;
     virtual LayoutUnit computeControlLogicalHeight(LayoutUnit lineHeight, LayoutUnit nonContentHeight) const OVERRIDE;
     virtual int baselinePosition(FontBaseline, bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const;
 
     virtual RenderStyle* textBaseStyle() const;
     virtual PassRefPtr<RenderStyle> createInnerTextStyle(const RenderStyle* startStyle) const;
     virtual RenderObject* layoutSpecialExcludedChild(bool relayoutChildren, SubtreeLayoutScope&);
 };
 
-inline RenderTextControlMultiLine* toRenderTextControlMultiLine(RenderObject* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isTextArea());
-    return static_cast<RenderTextControlMultiLine*>(object);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toRenderTextControlMultiLine(const RenderTextControlMultiLine*);
+DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderTextControlMultiLine, isTextArea());
 
 }
 
 #endif