nsIFrame* nextChild;
nsFrameContentIterator::Last(){  nsIFrame* nextChild;  // Starting with the first child walk and find the last child  mCurrentChild = nsnull;  mParentFrame->FirstChild(mPresContext, nsnull, &nextChild);  while (nextChild) {    mCurrentChild = nextChild;    nextChild = ::GetNextChildFrame(mPresContext, nextChild);  }  if (!mCurrentChild) {    return NS_ERROR_FAILURE;  }  mIsDone = PR_FALSE;  return NS_OK;}