Roll re2 596d73e..193486d and update OWNERS.

https://chromium.googlesource.com/external/github.com/google/re2.git/+log/596d73e..193486d

R=inferno@chromiu.org, tfarina@chromium.org, thakis@chromium.org
BUG=693507

Review-Url: https://codereview.chromium.org/2707673002
Cr-Commit-Position: refs/heads/master@{#451489}
NOKEYCHECK=True
GitOrigin-RevId: 7d820c7251c04d0ecfb7e587c14ec6891aa8955a