if (mLines) { nsLineBox* line = nsLineBox::LastLine(mLines); return line->LastChild();
nsIFrame* frame = mFirstChild; PRInt32 n = mChildCount - 1; while (--n >= 0) { frame->GetNextSibling(frame);
nsBlockFrame::LastChild(){  if (mLines) {    nsLineBox* line = nsLineBox::LastLine(mLines);    return line->LastChild();  }  return nsnull;}