Fix div-by-0 in NetEq's StatisticsCalculator

Fix div-by-0 in NetEq's StatisticsCalculator

If a StatisticsCalculator::PeriodicUmaAverage object was created and
then deleted without any samples being logged, the destructor would call
the Metric() method, which calculated sum_/counter_. However, with no
samples logged, counter_ is 0.

This was found and verified using UBSan tests; see the bug for more info.

BUG=webrtc:5490
R=ivoc@webrtc.org

Committed: https://crrev.com/e594213a2bb6006c41ff1ecc516afc9b024d19ad
Cr-Commit-Position: refs/heads/master@{#11534}

[hlundin-webrtc, 2016-02-08 14:26:52]

PTAL

[ivoc, 2016-02-08 14:28:26]

LGTM

[hlundin-webrtc, 2016-02-08 14:31:23]

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

[commit-bot: I haz the power, 2016-02-08 14:31:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1678773003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1678773003/1

[commit-bot: I haz the power, 2016-02-08 15:11:47]

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

[commit-bot: I haz the power, 2016-02-08 15:11:48]

Try jobs failed on following builders:
  linux_tsan2 on tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/linux_tsan2/builds/9701)

[hlundin-webrtc, 2016-02-08 15:13:25]

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

[commit-bot: I haz the power, 2016-02-08 15:13:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1678773003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1678773003/1

[commit-bot: I haz the power, 2016-02-08 16:31:56]

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

[commit-bot: I haz the power, 2016-02-08 16:31:57]

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

[hlundin-webrtc, 2016-02-09 07:59:35]

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

[commit-bot: I haz the power, 2016-02-09 07:59:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1678773003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1678773003/1

[commit-bot: I haz the power, 2016-02-09 08:35:58]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-02-09 08:36:08]

Description was changed from

==========
Fix div-by-0 in NetEq's StatisticsCalculator

If a StatisticsCalculator::PeriodicUmaAverage object was created and
then deleted without any samples being logged, the destructor would call
the Metric() method, which calculated sum_/counter_. However, with no
samples logged, counter_ is 0.

This was found and verified using UBSan tests; see the bug for more info.

BUG=webrtc:5490
R=ivoc@webrtc.org
==========

to

==========
Fix div-by-0 in NetEq's StatisticsCalculator

If a StatisticsCalculator::PeriodicUmaAverage object was created and
then deleted without any samples being logged, the destructor would call
the Metric() method, which calculated sum_/counter_. However, with no
samples logged, counter_ is 0.

This was found and verified using UBSan tests; see the bug for more info.

BUG=webrtc:5490
R=ivoc@webrtc.org

Committed: https://crrev.com/e594213a2bb6006c41ff1ecc516afc9b024d19ad
Cr-Commit-Position: refs/heads/master@{#11534}
==========

[commit-bot: I haz the power, 2016-02-09 08:36:09]

Patchset 1 (id:??) landed as
https://crrev.com/e594213a2bb6006c41ff1ecc516afc9b024d19ad
Cr-Commit-Position: refs/heads/master@{#11534}