Reland: Replace AudioFifo with a deque of AudioBus in ATR::AudioEncoder

Reland: Replace AudioFifo with a deque of AudioBus in ATR::AudioEncoder

Link to original CL: https://codereview.chromium.org/2854363002/

Original CL description:
This CL uses a std::deque<std::unique_ptr<media::AudioBus>> instead
of an AudioFifo, to avoid copying data needlessly.

The original CL was reverted due to failures in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyRAsSDVdmU3VzcGVjdGVkQ0wiMWNocm9taXVtLzhlM2YwOTY3OGZkMjE5OTY0OWZkZmRlMWJiOWNjMGVjNTUyNDAzMDkM

This reland CL zeroes out all channels of incoming audio bus.

BUG=724448

[Chandan, 2017-05-22 13:07:16]

The CQ bit was checked by c.padhi@samsung.com to run a CQ dry run

[commit-bot: I haz the power, 2017-05-22 13:07:25]

Dry run: 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, 2017-05-22 14:47:44]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-22 14:47:45]

Dry run: This issue passed the CQ dry run.

[Chandan, 2017-05-23 11:30:12]

Description was changed from

==========
ATRDeque

BUG=
==========

to

==========
Reland: Replace AudioFifo with a deque of AudioBus in ATR::AudioEncoder

Link to original CL: https://codereview.chromium.org/2854363002/

Original CL description:
This CL uses a std::deque<std::unique_ptr<media::AudioBus>> instead
of an AudioFifo, to avoid copying data needlessly.

The original CL was reverted due to failures in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3Itb...

This reland CL zeroes out all channels of incoming audio bus.

BUG=724448
==========