Revert of Re-enabling 720p WebRTC video quality test.

Revert of Re-enabling 720p WebRTC video quality test. (patchset #2 id:20001 of https://codereview.chromium.org/1367453002/ )

Reason for revert:
Still too slow for one of our win7 bots.

Original issue's description:
> Re-enabling 720p WebRTC video quality test.
>
> Closing the local streams seems to solve the buffer thrashing that's
> going on while gathering frames; this should stop the test from
> timing out on Windows.
>
> BUG=532918, webrtc:4986
>
> Committed: https://crrev.com/5743af3d0c098fa86f587269519e226ecce185e4
> Cr-Commit-Position: refs/heads/master@{#351034}

TBR=perkj@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=532918, webrtc:4986
Committed: https://crrev.com/f838038bfe998af36ffd03b0b977650dddba1cf1
Cr-Commit-Position: refs/heads/master@{#351057}

[phoglund_chromium, 2015-09-28 12:10:04]

Created Revert of Re-enabling 720p WebRTC video quality test.

[commit-bot: I haz the power, 2015-09-28 12:10:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1372923002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1372923002/1

[commit-bot: I haz the power, 2015-09-28 12:10:54]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-28 12:11:33]

Patchset 1 (id:??) landed as
https://crrev.com/f838038bfe998af36ffd03b0b977650dddba1cf1
Cr-Commit-Position: refs/heads/master@{#351057}