NS_ASSERTION((aSiblingIndex >= 0) == (aSiblingList != nsnull), "Cached sibling list and sibling index not in sync.");
if (mState.siblingIndex < 0) mState.siblingList = nsnull;
nsAccessibleTreeWalker::nsAccessibleTreeWalker(nsIWeakReference* aPresShell, nsIDOMNode* aNode, PRInt32 aSiblingIndex, nsIDOMNodeList *aSiblingList):   mPresShell(aPresShell), mAccService(do_GetService("@mozilla.org/accessibilityService;1")){  mState.domNode = aNode;  mState.siblingIndex = aSiblingIndex;  mState.prevState = nsnull;  mState.siblingList = aSiblingList;  NS_ASSERTION((aSiblingIndex >= 0) == (aSiblingList != nsnull), "Cached sibling list and sibling index not in sync.");  nsCOMPtr<nsIPresShell> shell(do_QueryReferent(mPresShell));  if (shell) {    nsCOMPtr<nsIDocument> doc;    shell->GetDocument(getter_AddRefs(doc));     doc->GetBindingManager(getter_AddRefs(mBindingManager));  }   MOZ_COUNT_CTOR(nsAccessibleTreeWalker);}