NS_PRECONDITION(PRInt32(mRefCnt) >= 0, "illegal refcnt"); ++mRefCnt; return mRefCnt;
return ++mRefCnt;
NS_IMETHODIMP_(nsrefcnt) nsWebShell::AddRef(void){  NS_PRECONDITION(PRInt32(mRefCnt) >= 0, "illegal refcnt");  ++mRefCnt;  return mRefCnt;}