Revert of Remove swap ack throttling to regain performance regression on freon

Revert of Remove swap ack throttling to regain performance regression on freon (patchset #4 id:80001 of https://codereview.chromium.org/1053153003/)

Reason for revert:
Despite throughput wins, this increased hang rates, broke pdfs, and regressed latency.

Original issue's description:
> Remove swap ack throttling to regain performance regression on freon.
>
> In the past eglSwapBuffers used to return early, before the swap actually happened and descheduling in the driver. This resulted in the scheduler beginning the next frame early and hitting the page flip deadline in time more often.
>
> Freon returns swap ack when page flip actually happened, but with the side effect of scheduling shifted forward, resulting in more missed vblanks and reduced performance.
>
> This change restores original performance on freon.
>
> BUG=465599
>
> Committed: https://crrev.com/faa924ff38e80006a27ac85fcc95f3dcbe441d55
> Cr-Commit-Position: refs/heads/master@{#324465}

TBR=danakj@chromium.org,skyostil@chromium.org,alexst@chromium.org
BUG=465599, 311213, 477082
Committed: https://crrev.com/ce413fbbfc4eb065a7591972d4f886099631880a
Cr-Commit-Position: refs/heads/master@{#325158}

[brianderson, 2015-04-14 22:39:24]

Created Revert of Remove swap ack throttling to regain performance regression on
freon

[brianderson, 2015-04-14 22:40:05]

The CQ bit was checked by brianderson@chromium.org

[commit-bot: I haz the power, 2015-04-14 22:40:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1087983003/1

[brianderson, 2015-04-14 22:40:35]

The CQ bit was unchecked by brianderson@chromium.org

[commit-bot: I haz the power, 2015-04-14 22:41:07]

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

[brianderson, 2015-04-14 22:43:20]

The CQ bit was checked by brianderson@chromium.org

[commit-bot: I haz the power, 2015-04-14 22:43:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1087983003/1

[commit-bot: I haz the power, 2015-04-15 00:39:49]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-15 00:40:46]

Patchset 1 (id:??) landed as
https://crrev.com/ce413fbbfc4eb065a7591972d4f886099631880a
Cr-Commit-Position: refs/heads/master@{#325158}