Implement ParentNode IDL interface

Source/core/dom/ContainerNode.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009, 2010, 2011 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.
@@ skipping 15 matching lines @@
 
 #include "core/dom/ExceptionCodePlaceholder.h"
 #include "core/dom/Node.h"
 
 #include <wtf/OwnPtr.h>
 #include <wtf/Vector.h>
 
 namespace WebCore {
 
 class FloatPoint;
-    
+class HTMLCollection;
+
 typedef void (*NodeCallback)(Node*, unsigned);
 
 namespace Private { 
     template<class GenericNode, class GenericNodeContainer>
     void addChildNodesToDeletionQueue(GenericNode*& head, GenericNode*& tail, GenericNodeContainer*);
 };
 
 class NoEventDispatchAssertion {
 public:
     NoEventDispatchAssertion()
@@ skipping 32 matching lines @@
 
 class ContainerNode : public Node {
     friend class PostAttachCallbackDisabler;
 public:
     virtual ~ContainerNode();
 
     Node* firstChild() const { return m_firstChild; }
     Node* lastChild() const { return m_lastChild; }
     bool hasChildNodes() const { return m_firstChild; }
 
+    // ParentNode interface API
+    PassRefPtr<HTMLCollection> children();
+    Element* firstElementChild() const;
+    Element* lastElementChild() const;
+    unsigned childElementCount() const;
+
     unsigned childNodeCount() const;
     Node* childNode(unsigned index) const;
 
     bool insertBefore(PassRefPtr<Node> newChild, Node* refChild, ExceptionCode& = ASSERT_NO_EXCEPTION, AttachBehavior = AttachNow);
     bool replaceChild(PassRefPtr<Node> newChild, Node* oldChild, ExceptionCode& = ASSERT_NO_EXCEPTION, AttachBehavior = AttachNow);
     bool removeChild(Node* child, ExceptionCode& = ASSERT_NO_EXCEPTION);
     bool appendChild(PassRefPtr<Node> newChild, ExceptionCode& = ASSERT_NO_EXCEPTION, AttachBehavior = AttachNow);
 
     // These methods are only used during parsing.
     // They don't send DOM mutation events or handle reparenting.
@@ skipping 253 matching lines @@
         m_node->resumePostAttachCallbacks();
     }
 
 private:
     ContainerNode* m_node;
 };
 
 } // namespace WebCore
 
 #endif // ContainerNode_h