Add Config struct for experimental AGC.

Disable in the audio mixer.

TBR=aluebs,bjornv
BUG=2844

Review URL: https://webrtc-codereview.appspot.com/7769004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@5454 4adac7df-926f-26a2-2b94-8c16560cd09d
2 files changed