Silence uninteresting proguard output.

Silence uninteresting proguard output.

ProGuard outputs boring stuff to stdout (proguard version, jar path,
etc) as well as interesting stuff (notes, warnings, etc). If stdout is
entirely boring, this method suppresses the output.

Committed: https://crrev.com/20e824209ff87f27e26d8c20bf20b5d0d6795d4e
Cr-Commit-Position: refs/heads/master@{#319183}

[newt (away), 2015-03-04 23:58:40]

newt@chromium.org changed reviewers:
+ cjhopman@chromium.org

[newt (away), 2015-03-04 23:58:40]

PTAL

[cjhopman, 2015-03-05 00:02:09]

lgtm

[newt (away), 2015-03-05 00:04:19]

The CQ bit was checked by newt@chromium.org

[commit-bot: I haz the power, 2015-03-05 00:05:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/977253002/1

[commit-bot: I haz the power, 2015-03-05 01:05:35]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-05 01:06:23]

Patchset 1 (id:??) landed as
https://crrev.com/20e824209ff87f27e26d8c20bf20b5d0d6795d4e
Cr-Commit-Position: refs/heads/master@{#319183}