CharT* startPos = GetWritableFragment(fragment, kFragmentAt, NS_MAX(0U, Length()-aOffset));
CharT* startPos = GetWritableFragment(fragment, kFragmentAt, NS_MAX(0U, this->Length()-aOffset));
      EndWriting( PRUint32 aOffset = 0 )        {          nsWritableFragment<CharT> fragment;          CharT* startPos = GetWritableFragment(fragment, kFragmentAt, NS_MAX(0U, Length()-aOffset));          return nsWritingIterator<CharT>(fragment, startPos, *this);        }