Get rid of inefficient uses of childNodeCount()

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 68 matching lines @@
 class ContainerNode : public Node {
 public:
     virtual ~ContainerNode();
 
     Node* firstChild() const { return m_firstChild; }
     Node* lastChild() const { return m_lastChild; }
     bool hasChildNodes() const { return m_firstChild; }
 
     bool hasOneChild() const { return m_firstChild && !m_firstChild->nextSibling(); }
     bool hasOneTextChild() const { return hasOneChild() && m_firstChild->isTextNode(); }
+    bool hasChildCount(unsigned) const;
 
     PassRefPtr<HTMLCollection> children();
 
     unsigned childNodeCount() const;
     Node* childNode(unsigned index) const;
 
     PassRefPtr<Element> querySelector(const AtomicString& selectors, ExceptionState&);
     PassRefPtr<NodeList> querySelectorAll(const AtomicString& selectors, ExceptionState&);
 
     void insertBefore(PassRefPtr<Node> newChild, Node* refChild, ExceptionState& = ASSERT_NO_EXCEPTION);
@@ skipping 70 matching lines @@
     Node* m_firstChild;
     Node* m_lastChild;
 };
 
 #ifndef NDEBUG
 bool childAttachedAllowedWhenAttachingChildren(ContainerNode*);
 #endif
 
 DEFINE_NODE_TYPE_CASTS(ContainerNode, isContainerNode());
 
+inline bool ContainerNode::hasChildCount(unsigned count) const
+{
+    Node* child = m_firstChild;
+    while (count && child) {
+        child = child->nextSibling();
+        --count;
+    }
+    return !count && !child;
+}
+
 inline ContainerNode::ContainerNode(TreeScope* treeScope, ConstructionType type)
     : Node(treeScope, type)
     , m_firstChild(0)
     , m_lastChild(0)
 {
 }
 
 inline void ContainerNode::attachChildren(const AttachContext& context)
 {
     AttachContext childrenContext(context);
@@ skipping 132 matching lines @@
 
     RefPtr<Node> m_currentNode;
     unsigned m_currentIndex;
     OwnPtr<Vector<RefPtr<Node> > > m_childNodes; // Lazily instantiated.
     ChildNodesLazySnapshot* m_nextSnapshot;
 };
 
 } // namespace WebCore
 
 #endif // ContainerNode_h