Use C++11 features in core/html

Source/core/html/HTMLTableColElement.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, 2010 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
@@ skipping 64 matching lines @@
                     col->setNeedsLayoutAndPrefWidthsRecalcAndFullPaintInvalidation();
             }
         }
     } else
         HTMLTablePartElement::parseAttribute(name, value);
 }
 
 const StylePropertySet* HTMLTableColElement::additionalPresentationAttributeStyle()
 {
     if (!hasTagName(colgroupTag))
-        return 0;
+        return nullptr;
     if (HTMLTableElement* table = findParentTable())
         return table->additionalGroupStyle(false);
-    return 0;
+    return nullptr;
 }
 
 void HTMLTableColElement::setSpan(int n)
 {
     setIntegralAttribute(spanAttr, n);
 }
 
 const AtomicString& HTMLTableColElement::width() const
 {
     return getAttribute(widthAttr);
 }
 
 }