VAD changes ported to ACM2.

This CL ports the relevant parts of  https://code.google.com/p/webrtc/source/detail?r=4625 to ACM2.

BUG=
R=tina.legrand@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2264004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4804 4adac7df-926f-26a2-2b94-8c16560cd09d
4 files changed