Revert of Disable RunsAudioVideoWebRTCCallInTwoTabs so blink can roll

Revert of Disable RunsAudioVideoWebRTCCallInTwoTabs so blink can roll (patchset #1 id:1 of https://codereview.chromium.org/1148873003/)

Reason for revert:
Re-enabling after reverting breaking change.

BUG=490368
Original issue's description:
> Disable RunsAudioVideoWebRTCCallInTwoTabs so blink can roll
>
> This failure has been preventing blink from rolling for >12 hours.
> Sample failure:
>
> http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_rel_ng/builds/66651
>
> TBR=cevans@chromium.org,haraken@chromium.org
> NOTRY=true
> BUG=
>
> Committed: https://crrev.com/44cafa04c9c11b4ac32c99d39177be62b0a7acd3
> Cr-Commit-Position: refs/heads/master@{#330763}

TBR=cevans@chromium.org,haraken@chromium.org,szager@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/692979285996f271ce80aef4677eb56a3b7ed4dd
Cr-Commit-Position: refs/heads/master@{#331270}

[phoglund_chromium, 2015-05-25 09:21:33]

Created Revert of Disable RunsAudioVideoWebRTCCallInTwoTabs so blink can roll

[commit-bot: I haz the power, 2015-05-25 09:21:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1152333004/1

[commit-bot: I haz the power, 2015-05-25 09:22:07]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-25 09:23:17]

Patchset 1 (id:??) landed as
https://crrev.com/692979285996f271ce80aef4677eb56a3b7ed4dd
Cr-Commit-Position: refs/heads/master@{#331270}

[haraken, 2015-05-25 09:31:47]

LGTM