return NS_ERROR_ILLEGAL_VALUE; }
  nsresult  GetCounterIncrementAt(PRUint32 aIndex, nsString& aCounter, PRInt32& aIncrement) const {    if (aIndex < mIncrementCount) {      aCounter = mIncrements[aIndex].mCounter;      aIncrement = mIncrements[aIndex].mValue;      return NS_OK;    }    return NS_ERROR_ILLEGAL_VALUE;  }