nsAString::size_type src_len = aSource.Length(), sub_len = aSubstring.Length();
nsACString::size_type src_len = aSource.Length(), sub_len = aSubstring.Length();
StringEndsWith( const nsAString& aSource, const nsAString& aSubstring)  {    nsAString::size_type src_len = aSource.Length(),                         sub_len = aSubstring.Length();    if (sub_len > src_len)      return PR_FALSE;    return Substring(aSource, src_len - sub_len, sub_len) == aSubstring;  }