Use new is*Element() helper functions more in rendering code

Source/core/rendering/RenderFieldset.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006 Apple Computer, Inc.
  *
  * 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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #include "config.h"
 #include "core/rendering/RenderFieldset.h"
 
 #include "CSSPropertyNames.h"
 #include "HTMLNames.h"
+#include "core/html/HTMLLegendElement.h"
 #include "core/rendering/PaintInfo.h"
 #include "platform/graphics/GraphicsContextStateSaver.h"
 
 using std::min;
 using std::max;
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
@@ skipping 83 matching lines @@
     }
     return legend;
 }
 
 RenderBox* RenderFieldset::findLegend(FindLegendOption option) const
 {
     for (RenderObject* legend = firstChild(); legend; legend = legend->nextSibling()) {
         if (option == IgnoreFloatingOrOutOfFlow && legend->isFloatingOrOutOfFlowPositioned())
             continue;
 
-        if (legend->node() && (legend->node()->hasTagName(legendTag)))
+        if (isHTMLLegendElement(legend->node()))
             return toRenderBox(legend);
     }
     return 0;
 }
 
 void RenderFieldset::paintBoxDecorations(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     if (!paintInfo.shouldPaintWithinRoot(this))
         return;
 
@@ skipping 63 matching lines @@
     } else {
         LayoutUnit xOff = (legend->x() > 0) ? LayoutUnit() : (legend->width() - borderLeft()) / 2;
         paintRect.expand(-xOff, 0);
         paintRect.move(xOff, 0);
     }
 
     paintMaskImages(paintInfo, paintRect);
 }
 
 } // namespace WebCore