Wiring discard rate of audio FEC/RED packets up to StatsReport.

BUG=webrtc:7903

Change-Id: I0325725be354ab89cfce1d3564936fe5ff93d303
Reviewed-on: https://chromium-review.googlesource.com/559339
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Commit-Queue: Minyue Li <minyue@webrtc.org>
Cr-Original-Commit-Position: refs/heads/master@{#19560}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 0e320ec5baf3a0845cfef5d3a347501093aeeaad
11 files changed