nsIFrame *prevInFlow = nsnull; aFrame->GetPrevInFlow(&prevInFlow);
nsIFrame *prevInFlow = aFrame->GetPrevInFlow();
  void SetFrame(nsIFrame* aFrame)  {    NS_PRECONDITION(aFrame, "Need a frame");    nsIFrame *prevInFlow = nsnull;    aFrame->GetPrevInFlow(&prevInFlow);    if (!prevInFlow || mFrame != prevInFlow) {      // Ok, we've got the wrong frame.  We have to start from scratch.      Reset();      Init(aFrame);      return;    }    // Get our last frame's size and add its width to our continuation    // point before we cache the new frame.    mContinuationPoint += mFrame->GetSize().width;    mFrame = aFrame;  }