Re-add kUseGpuInTests flag in WebRTC browser tests.

Re-add kUseGpuInTests flag in WebRTC browser tests.

This reverts the removal of the kUseGpuInTests flags done in
https://crrev.com/cf04d9696a7f1f321294bc0970037ddb23c1204d
since it seems this affected performance results.
It also adds it to the new chrome/browser/media/chrome_webrtc_simulcast_browsertest.cc
test.

BUG=452654, 452655
Committed: https://crrev.com/0d6e89ba9d5d66adf5dcd8c46682c5a1901844c3
Cr-Commit-Position: refs/heads/master@{#313475}

[kjellander_chromium, 2015-01-28 08:14:58]

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

[kjellander_chromium, 2015-01-28 08:14:58]

Do you think we need to add the flag for
chrome/browser/media/chrome_webrtc_simulcast_browsertest.cc as well?
I had to disable it on Windows yesterday, see
https://codereview.chromium.org/882713003/

[phoglund_chromium, 2015-01-28 08:46:56]

lgtm

[phoglund_chromium, 2015-01-28 08:47:21]

On 2015/01/28 08:14:58, kjellander wrote:
> Do you think we need to add the flag for
> chrome/browser/media/chrome_webrtc_simulcast_browsertest.cc as well?
> I had to disable it on Windows yesterday, see
> https://codereview.chromium.org/882713003/

I think that might be a good idea.

[kjellander_chromium, 2015-01-28 08:56:56]

The CQ bit was checked by kjellander@chromium.org

[commit-bot: I haz the power, 2015-01-28 08:57:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/879223002/20001

[commit-bot: I haz the power, 2015-01-28 10:53:05]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-01-28 10:53:52]

Patchset 2 (id:??) landed as
https://crrev.com/0d6e89ba9d5d66adf5dcd8c46682c5a1901844c3
Cr-Commit-Position: refs/heads/master@{#313475}