Adding two new stats to VoiceReceiverInfo

There have been requests of two new stats namely

speech_expand_rate and secondary_decoded_rate.

BUG=3867
R=henrik.lundin@webrtc.org, henrika@webrtc.org, tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/40789004

Cr-Original-Commit-Position: refs/heads/master@{#8415}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c0bd7be0df67735d63f5cdd302a3b85f88239874
13 files changed