NS_IF_ADDREF(mAtom); if (aCopy.mNext) { mNext = new nsHTMLClassList(*(aCopy.mNext)); }
  nsHTMLClassList(const nsHTMLClassList& aCopy)    : mAtom(aCopy.mAtom),      mNext(nsnull)  {    MOZ_COUNT_CTOR(nsHTMLClassList);    NS_IF_ADDREF(mAtom);    if (aCopy.mNext) {      mNext = new nsHTMLClassList(*(aCopy.mNext));    }  }