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

Source/core/rendering/RenderTableCol.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 42 matching lines @@
         RenderTable* table = this->table();
         if (table && !table->selfNeedsLayout() && !table->normalChildNeedsLayout() && oldStyle && oldStyle->border() != style()->border())
             table->invalidateCollapsedBorders();
     }
 }
 
 void RenderTableCol::updateFromElement()
 {
     unsigned oldSpan = m_span;
     Node* n = node();
-    if (n && (n->hasTagName(colTag) || n->hasTagName(colgroupTag))) {
-        HTMLTableColElement* tc = toHTMLTableColElement(n);
-        m_span = tc->span();
+    if (n && isHTMLTableColElement(*n)) {
+        HTMLTableColElement& tc = toHTMLTableColElement(*n);
+        m_span = tc.span();
     } else
         m_span = !(style() && style()->display() == TABLE_COLUMN_GROUP);
     if (m_span != oldSpan && style() && parent())
         setNeedsLayoutAndPrefWidthsRecalc();
 }
 
 void RenderTableCol::insertedIntoTree()
 {
     RenderBox::insertedIntoTree();
     table()->addColumn(this);
@@ skipping 98 matching lines @@
     return style()->borderStart();
 }
 
 const BorderValue& RenderTableCol::borderAdjoiningCellAfter(const RenderTableCell* cell) const
 {
     ASSERT_UNUSED(cell, table()->colElement(cell->col() - 1) == this);
     return style()->borderEnd();
 }
 
 }