return NS_ERROR_ILLEGAL_VALUE; }
  nsresult  SetContentAt(PRUint32 aIndex, nsStyleContentType aType, const nsString& aContent) {    if (aIndex < mContentCount) {      mContents[aIndex].mType = aType;      if (aType < eStyleContentType_OpenQuote) {        mContents[aIndex].mContent = aContent;      }      else {        mContents[aIndex].mContent.Truncate();      }      return NS_OK;    }    return NS_ERROR_ILLEGAL_VALUE;  }