Remove callback_cs_ in ViEEncoder.

Remove callback_cs_ in ViEEncoder.

Instead make callbacks const and set on construction.

BUG=webrtc:1695
R=philipel@webrtc.org

Committed: https://crrev.com/7083e119e8f39d2ec9e504461c1bb6e0bc6be5ff
Cr-Commit-Position: refs/heads/master@{#10017}

[pbos-webrtc, 2015-09-22 10:24:39]

PTAL woo!

[pbos-webrtc, 2015-09-22 10:24:43]

The CQ bit was checked by pbos@webrtc.org to run a CQ dry run

[commit-bot: I haz the power, 2015-09-22 10:24:49]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1354143004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1354143004/1

[commit-bot: I haz the power, 2015-09-22 10:39:42]

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

[commit-bot: I haz the power, 2015-09-22 10:39:43]

Dry run: Try jobs failed on following builders:
  linux_asan on tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/linux_asan/builds/9462)

[philipel, 2015-09-22 14:06:20]

On 2015/09/22 10:39:43, commit-bot: I haz the power wrote:
> Dry run: Try jobs failed on following builders:
>   linux_asan on tryserver.webrtc (JOB_FAILED,
> http://build.chromium.org/p/tryserver.webrtc/builders/linux_asan/builds/9462)

lgtm

[pbos-webrtc, 2015-09-22 14:29:06]

Committed patchset #1 (id:1) manually as
7083e119e8f39d2ec9e504461c1bb6e0bc6be5ff (presubmit successful).

[commit-bot: I haz the power, 2015-09-22 14:29:10]

Patchset 1 (id:??) landed as
https://crrev.com/7083e119e8f39d2ec9e504461c1bb6e0bc6be5ff
Cr-Commit-Position: refs/heads/master@{#10017}