Get rid of inefficient uses of childNodeCount()

Source/core/dom/Range.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Gunnstein Lye (gunnstein@netcom.no)
  * (C) 2000 Frederik Holljen (frederik.holljen@hig.no)
  * (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Motorola Mobility. 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 639 matching lines @@
     switch (node->nodeType()) {
     case Node::TEXT_NODE:
     case Node::CDATA_SECTION_NODE:
     case Node::COMMENT_NODE:
         return toCharacterData(node)->length();
     case Node::PROCESSING_INSTRUCTION_NODE:
         return toProcessingInstruction(node)->data().length();
     case Node::ELEMENT_NODE:
     case Node::ATTRIBUTE_NODE:
     case Node::DOCUMENT_NODE:
+    case Node::DOCUMENT_FRAGMENT_NODE:
+        return toContainerNode(node)->childNodeCount();
     case Node::DOCUMENT_TYPE_NODE:
-    case Node::DOCUMENT_FRAGMENT_NODE:
-        return node->childNodeCount();
+        return 0;
     }
     ASSERT_NOT_REACHED();
     return 0;
 }
 
 PassRefPtr<DocumentFragment> Range::processContents(ActionType action, ExceptionState& exceptionState)
 {
     typedef Vector<RefPtr<Node> > NodeVector;
 
     RefPtr<DocumentFragment> fragment;
@@ skipping 1213 matching lines @@
 
 void showTree(const WebCore::Range* range)
 {
     if (range && range->boundaryPointsValid()) {
         range->startContainer()->showTreeAndMark(range->startContainer(), "S", range->endContainer(), "E");
         fprintf(stderr, "start offset: %d, end offset: %d\n", range->startOffset(), range->endOffset());
     }
 }
 
 #endif