ClassRootNodeList should start from rootNode, not the first child of rootNode.

Source/core/dom/SelectorQuery.cpp

 /*
  * Copyright (C) 2011 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
@@ skipping 46 matching lines @@
         m_currentNode = 0;
         return current;
     }
 
 private:
     Node* m_currentNode;
 };
 
 class ClassRootNodeList : public SimpleNodeList {
 public:
-    explicit ClassRootNodeList(Node* rootNode, const AtomicString& className)
+    ClassRootNodeList(Node* rootNode, const AtomicString& className)
         : m_className(className)
         , m_rootNode(rootNode)
-        , m_currentElement(nextInternal(ElementTraversal::firstWithin(rootNode))) { }
+        , m_currentElement(nextInternal(rootNode && rootNode->isElementNode() ? toElement(rootNode) : ElementTraversal::firstWithin(rootNode))) { }
 
     bool isEmpty() const { return !m_currentElement; }
 
     Node* next()
     {
         Node* current = m_currentElement;
         ASSERT(current);
         m_currentElement = nextInternal(ElementTraversal::nextSkippingChildren(m_currentElement, m_rootNode));
         return current;
     }
 
 private:
     Element* nextInternal(Element* element)
     {
         for (; element; element = ElementTraversal::next(element, m_rootNode)) {
             if (element->hasClass() && element->classNames().contains(m_className))
                 return element;
         }
         return 0;
     }
 
     const AtomicString& m_className;
     Node* m_rootNode;
     Element* m_currentElement;
 };
 
 class ClassElementList : public SimpleNodeList {
 public:
-    explicit ClassElementList(Node* rootNode, const AtomicString& className)
+    ClassElementList(Node* rootNode, const AtomicString& className)
         : m_className(className)
         , m_rootNode(rootNode)
         , m_currentElement(nextInternal(ElementTraversal::firstWithin(rootNode))) { }
 
     bool isEmpty() const { return !m_currentElement; }
 
     Node* next()
     {
         Node* current = m_currentElement;
         ASSERT(current);
@@ skipping 400 matching lines @@
     m_entries.add(selectors, selectorQuery.release());
     return rawSelectorQuery;
 }
 
 void SelectorQueryCache::invalidate()
 {
     m_entries.clear();
 }
 
 }