Use default argument value instead of overloading for MarkupAccumulator::serializeNodes()

Source/core/editing/MarkupAccumulator.h

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 52 matching lines @@
     EntityMask mask;
 };
 
 class MarkupAccumulator {
     WTF_MAKE_NONCOPYABLE(MarkupAccumulator);
 
 public:
     MarkupAccumulator(Vector<Node*>*, EAbsoluteURLs, const Range* = 0);
     virtual ~MarkupAccumulator();
 
-    String serializeNodes(Node* targetNode, EChildrenOnly);
-    String serializeNodes(Node* targetNode, EChildrenOnly, Vector<QualifiedName>* tagNamesToSkip);
+    String serializeNodes(Node* targetNode, EChildrenOnly, Vector<QualifiedName>* tagNamesToSkip = 0);
 
     static void appendComment(StringBuilder&, const String&);
 
     static void appendCharactersReplacingEntities(StringBuilder&, const String&, unsigned, unsigned, EntityMask);
 
 protected:
     virtual void appendString(const String&);
     void appendStartTag(Node*, Namespaces* = 0);
     virtual void appendEndTag(Node*);
     static size_t totalLength(const Vector<String>&);
@@ skipping 28 matching lines @@
     void appendQuotedURLAttributeValue(StringBuilder&, const Element*, const Attribute&);
     void serializeNodesWithNamespaces(Node* targetNode, EChildrenOnly, const Namespaces*, Vector<QualifiedName>* tagNamesToSkip);
 
     StringBuilder m_markup;
     const EAbsoluteURLs m_resolveURLsMethod;
 };
 
 }
 
 #endif