NetEq: Implement counting of Delayed Packet Outage Events per minute

NetEq: Implement counting of Delayed Packet Outage Events per minute

This CL adds a counter for delayed packet outage events. The counter
is restarted every minute, and the result is logged to the UMA stat
WebRTC.Audio.DelayedPacketOutageEventsPerMinute.  For a description of
delayed packet outages, see previous CL implementing a duration log
for these events.

BUG=webrtc:4915, chromium:488124

[hlundin-webrtc, 2015-08-14 21:05:33]

henrik.lundin@webrtc.org changed reviewers:
+ ivoc@webrtc.org, minyue@webrtc.org

[hlundin-webrtc, 2015-08-14 21:05:33]

Minyue, Ivo,

Please, take a look at this CL. This is number two in the series adding new
metrics to NetEq.

Thanks!

[hlundin-webrtc, 2015-08-18 13:32:18]

On 2015/08/14 21:05:33, hlundin-webrtc wrote:
> Minyue, Ivo,
> 
> Please, take a look at this CL. This is number two in the series adding new
> metrics to NetEq.
> 
> Thanks!

This CL is replaced by https://codereview.webrtc.org/1287333005/.
Closing.