Reland: Implement NetEq's CurrentDelay function

Reland: Implement NetEq's CurrentDelay function

This was not implemented before. It returns the current total delay
(packet buffer and sync buffer) of NetEq. This is the same information
that was already available in
NetEqNetworkStatistics::current_buffer_size_ms, that can be obtained
through NetEq::NetworkStatistics(). But, since the current delay is a
key metric of NetEq, it is convenient to have it available in a
simpler way.

This is a re-landing of r9359,
https://webrtc-codereview.appspot.com/51149004, which was reverted in
r9360. The refactoring made in r9669 facilitated the relanding.

TBR=minyue@webrtc.org

Committed: https://crrev.com/9c3efd00523a81d0f2b582799fbe67afe44139b2
Cr-Commit-Position: refs/heads/master@{#9801}

[minyue-webrtc, 2015-08-25 11:45:04]

may better rename to "Reland ..."

[hlundin-webrtc, 2015-08-25 12:09:35]

On 2015/08/25 11:45:04, minyue-webrtc wrote:
> may better rename to "Reland ..."

Of course. Thanks!

[hlundin-webrtc, 2015-08-26 19:18:54]

The CQ bit was checked by henrik.lundin@webrtc.org

[commit-bot: I haz the power, 2015-08-26 19:19:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1313873003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1313873003/1

[commit-bot: I haz the power, 2015-08-26 19:25:02]

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

[commit-bot: I haz the power, 2015-08-26 19:25:03]

Try jobs failed on following builders:
  win_x64_gn on tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/win_x64_gn/builds/3643)

[hlundin-webrtc, 2015-08-27 11:36:20]

Fixing win64 build

[hlundin-webrtc, 2015-08-27 11:40:39]

The CQ bit was checked by henrik.lundin@webrtc.org

[commit-bot: I haz the power, 2015-08-27 11:40:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1313873003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1313873003/20001

[commit-bot: I haz the power, 2015-08-27 13:40:57]

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

[commit-bot: I haz the power, 2015-08-27 13:40:58]

Try jobs failed on following builders:
  android on tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  android_rel on tryserver.webrtc (JOB_TIMED_OUT, no build URL)

[hlundin-webrtc, 2015-08-27 20:11:29]

The CQ bit was checked by henrik.lundin@webrtc.org

[commit-bot: I haz the power, 2015-08-27 20:11:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1313873003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1313873003/20001

[commit-bot: I haz the power, 2015-08-27 20:12:27]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-08-27 20:12:37]

Patchset 2 (id:??) landed as
https://crrev.com/9c3efd00523a81d0f2b582799fbe67afe44139b2
Cr-Commit-Position: refs/heads/master@{#9801}