Fix Cast Streaming regression caused by enabling H264 HW encoder on Mac.

Fix Cast Streaming regression caused by enabling H264 HW encoder on Mac.

A recent commit (3956fa1cac34dd5682c271d77463accdd7191102) turned on
detection and use of the H264 hardware encoder for Mac desktop.  This
caused breakage in the form of a "black screen."  This change reverts to
the prior behavior of always using the software VP8 encoder on Macs.

BUG=596674
Committed: https://crrev.com/5f6bf2ab1d3619432d6d0a5021008d500b7e1c37
Cr-Commit-Position: refs/heads/master@{#382432}

[miu, 2016-03-21 21:57:30]

miu@chromium.org changed reviewers:
+ emircan@chromium.org

[emircan, 2016-03-21 22:01:42]

lgtm

[miu, 2016-03-21 22:04:26]

The CQ bit was checked by miu@chromium.org

[commit-bot: I haz the power, 2016-03-21 22:04:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1818203002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1818203002/1

[commit-bot: I haz the power, 2016-03-21 23:20:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-03-21 23:23:08]

Description was changed from

==========
Fix Cast Streaming regression caused by enabling H264 HW encoder on Mac.

A recent commit (3956fa1cac34dd5682c271d77463accdd7191102) turned on
detection and use of the H264 hardware encoder for Mac desktop.  This
caused breakage in the form of a "black screen."  This change reverts to
the prior behavior of always using the software VP8 encoder on Macs.

BUG=596674
==========

to

==========
Fix Cast Streaming regression caused by enabling H264 HW encoder on Mac.

A recent commit (3956fa1cac34dd5682c271d77463accdd7191102) turned on
detection and use of the H264 hardware encoder for Mac desktop.  This
caused breakage in the form of a "black screen."  This change reverts to
the prior behavior of always using the software VP8 encoder on Macs.

BUG=596674

Committed: https://crrev.com/5f6bf2ab1d3619432d6d0a5021008d500b7e1c37
Cr-Commit-Position: refs/heads/master@{#382432}
==========

[commit-bot: I haz the power, 2016-03-21 23:23:09]

Patchset 1 (id:??) landed as
https://crrev.com/5f6bf2ab1d3619432d6d0a5021008d500b7e1c37
Cr-Commit-Position: refs/heads/master@{#382432}