Filter out log lines when parsing output of --gtest_list_tests.

Filter out log lines when parsing output of --gtest_list_tests.

This patch makes the Chromium apptest runner resilient to missing apps
(e.g. tracing.mojo) polluting the output of mojo_shell that it tries to
parse.

BUG=450356
TBR=jamesr@chromium.org

Committed: https://crrev.com/554d1a97e618d951e5b30132b69ec51515d6839d
Cr-Commit-Position: refs/heads/master@{#314134}

[ppi, 2015-02-02 11:11:51]

ppi@chromium.org changed reviewers:
+ qsr@chromium.org

[ppi, 2015-02-02 11:12:05]

Hi Ben,

ptal.

[qsr, 2015-02-02 12:01:39]

lgtm

[ppi, 2015-02-02 12:20:38]

ppi@chromium.org changed reviewers:
+ jamesr@chromium.org

[ppi, 2015-02-02 12:21:59]

Thanks. I'm sending out https://codereview.chromium.org/892103004/ so that we
don't need to wait or TBR such changes.

[ppi, 2015-02-02 12:22:57]

The CQ bit was checked by ppi@chromium.org

[commit-bot: I haz the power, 2015-02-02 12:23:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/892933002/1

[commit-bot: I haz the power, 2015-02-02 13:26:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-02 13:27:12]

Patchset 1 (id:??) landed as
https://crrev.com/554d1a97e618d951e5b30132b69ec51515d6839d
Cr-Commit-Position: refs/heads/master@{#314134}

[jamesr, 2015-02-03 05:03:39]

Shouldn't this sort of thing be in some generic part of the apptest framework in
the public sdk?  This isn't a chromium-specific behavior.

[ppi, 2015-02-03 08:38:11]

I think so. As discussed on https://codereview.chromium.org/878933003/ , this
doesn't seem straightforward.

Filed http://crbug.com/454718 to follow up on that.