nsAWritableString& aDest )
nsAString& aDest )
AppendUnicodeTo( const nsReadingIterator<PRUnichar>& aSrcStart,                 const nsReadingIterator<PRUnichar>& aSrcEnd,                 nsAWritableString& aDest )  {    nsWritingIterator<PRUnichar> writer;    PRUint32 oldLength = aDest.Length();    aDest.SetLength(oldLength + Distance(aSrcStart, aSrcEnd));    aDest.BeginWriting(writer).advance(oldLength);    nsReadingIterator<PRUnichar> fromBegin(aSrcStart);        copy_string(fromBegin, aSrcEnd, writer);  }