Fix the script used to roll GN.

This updates the script to handle the latest inconsistencies in
the buildbot step logging, and also removes the CQ_EXTRA_TRYBOTS
logic for the old builders.

R=brettw@chromium.org

Review-Url: https://codereview.chromium.org/2120673003
Cr-Original-Commit-Position: refs/heads/master@{#403693}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 061d24c115ac682e388c25fbccdd012fbb7c1a63
1 file changed
tree: d6ac747acbb8c2c2984389873a9b6e30fd5ebca0
  1. tools/