Add a TBR= field to enable automated rolling. In some cases, add a committer to the field, for other rolls: leave it empty. Always run 'git pull', even if --dry-run is specified, as it is often used to just generate an updated commit message to update an existing CL with when updating it to match fixes in Chromium. BUG=webrtc:4688 R=phoglund@webrtc.org Review URL: https://codereview.webrtc.org/1369333010 . Cr-Commit-Position: refs/heads/master@{#10140}