Pass rootNode by reference when constructing node lists / collections

Source/core/dom/ChildNodeList.cpp

 /*
  * 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, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Samsung Electronics. 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
@@ skipping 11 matching lines @@
  */
 
 #include "config.h"
 #include "core/dom/ChildNodeList.h"
 
 #include "core/dom/Element.h"
 #include "core/dom/NodeRareData.h"
 
 namespace WebCore {
 
-ChildNodeList::ChildNodeList(PassRefPtr<ContainerNode> parent)
+ChildNodeList::ChildNodeList(ContainerNode& parent)
     : m_parent(parent)
 {
-    ASSERT(m_parent);
 }
 
 Node* ChildNodeList::virtualOwnerNode() const
 {
     return &ownerNode();
 }
 
 ChildNodeList::~ChildNodeList()
 {
     m_parent->nodeLists()->removeChildNodeList(this);
 }
 
 Node* ChildNodeList::itemBefore(const Node* previous) const
 {
     return LIKELY(!!previous) ? previous->previousSibling() : rootNode().lastChild();
 }
 
 Node* ChildNodeList::traverseForwardToOffset(unsigned offset, Node& currentNode, unsigned& currentOffset, const ContainerNode&) const
 {
     ASSERT(currentOffset < offset);
     Node* next = &currentNode;
     while ((next = next->nextSibling())) {
         if (++currentOffset == offset)
             return next;
     }
     return 0;
 }
 
 } // namespace WebCore