Print pooler crashes for some page ranges.

1. The print spooler fails to parse page ranges that end with
   a dash, e,g, "1-", which are however valid inputs since the
   user can continue typing to end up with a well-fromed range.

2. After a layout we are asking for the first selected page
   to be written emulating print preview, thus increasing the
   changes that apps will correctly implement the APIs.

bug:10743632

Change-Id: Ia74172d4fa6bce6ad93a0bc53da1aaa3fe8bef42