Implementing WebRTC audio quality test for Mac.

Implementing WebRTC audio quality test for Mac.

This makes the test described in http://goo.gl/umvzMt run on Mac.
It relies on Soundflower to loop audio from output to input so that rec
picks up the right audio.

The new gs resource files have been added to their respective buckets.

Note: this patch doesn't enable the tests. I need to configure the bots
first with sox and soundflower before I do that.

BUG=418034
Committed: https://crrev.com/d5597f9c656723040a1c04b2710f64fbd6f5041e
Cr-Commit-Position: refs/heads/master@{#296917}

[phoglund_chromium, 2014-09-26 09:28:17]

phoglund@chromium.org changed reviewers:
+ xians@chromium.org

[phoglund_chromium, 2014-09-26 10:02:52]

phoglund@chromium.org changed reviewers:
+ vrk@chromium.org
- xians@chromium.org

[vrk (LEFT CHROMIUM), 2014-09-26 10:09:56]

The CQ bit was checked by vrk@chromium.org

[vrk (LEFT CHROMIUM), 2014-09-26 10:09:56]

lgtm

[commit-bot: I haz the power, 2014-09-26 10:10:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/611433002/20001

[commit-bot: I haz the power, 2014-09-26 11:19:18]

Committed patchset #2 (id:20001) as b08dd0e8cfaed125800b6399c780013946ea475e

[commit-bot: I haz the power, 2014-09-26 11:19:58]

Patchset 2 (id:??) landed as
https://crrev.com/d5597f9c656723040a1c04b2710f64fbd6f5041e
Cr-Commit-Position: refs/heads/master@{#296917}