states that: "The winner of each Division will be determined by the record in all Conference games played (both interdivisional and intra-divisional) within the Conference. In the event of a tie, the following procedures will be applied to determine the Pac-12 Championship Game representatives" and it then goes on to list them.
http://championships.pac-12.org/wp-content/uploads/2014/09/2016-17-P12-Handbook.v3.pdf
The conference record alone determines division winners. If there is a tie in division winners, the tiebreakers kick in for CCG selection.