LogDog/Butler: Enable direct output forwarding.

LogDog/Butler: Enable direct output forwarding.

Currently, Butler supports either passing a subprocess' STDOUT/STDERR
directly as a LogDog stream or completely ignoring them. This adds a
third option: forwarding them through the Butler's STDOUT/STDERR.

BUG=chromium:643243
TEST=local
  - Ran locally, seems to work.

Committed: https://github.com/luci/luci-go/commit/11daeac05bb27ba6a5322cb653e06285fcff7040

[dnj, 2016-09-07 18:45:49]

dnj@chromium.org changed reviewers:
+ iannucci@chromium.org

[dnj, 2016-09-07 18:45:50]

PTAL!

[iannucci, 2016-09-07 19:03:58]

lgtm

[dnj, 2016-09-07 19:07:47]

The CQ bit was checked by dnj@chromium.org

[commit-bot: I haz the power, 2016-09-07 19:07:52]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-07 19:15:15]

Description was changed from

==========
LogDog/Butler: Enable direct output forwarding.

Currently, Butler supports either passing a subprocess' STDOUT/STDERR
directly as a LogDog stream or completely ignoring them. This adds a
third option: forwarding them through the Butler's STDOUT/STDERR.

BUG=chromium:643243
TEST=local
  - Ran locally, seems to work.
==========

to

==========
LogDog/Butler: Enable direct output forwarding.

Currently, Butler supports either passing a subprocess' STDOUT/STDERR
directly as a LogDog stream or completely ignoring them. This adds a
third option: forwarding them through the Butler's STDOUT/STDERR.

BUG=chromium:643243
TEST=local
  - Ran locally, seems to work.

Committed:
https://github.com/luci/luci-go/commit/11daeac05bb27ba6a5322cb653e06285fcff7040
==========

[commit-bot: I haz the power, 2016-09-07 19:15:15]

Committed patchset #1 (id:1) as
https://github.com/luci/luci-go/commit/11daeac05bb27ba6a5322cb653e06285fcff7040