Fix rebaseline-o-matic logging.

We'd miss any output between the last poll and the end of
the process.

Also, print out the log lines so that you can see them when
looking at the local log.

BUG=382248

Review URL: https://codereview.chromium.org/327633003

git-svn-id: svn://svn.chromium.org/blink/trunk@176135 bbb929c8-8fbe-4397-9dbb-9b2b20218538