Re-land "Switch to using AudioEncoderIsac instead of ACMISAC"

It should work now, after the fix in r8431.

Previously committed in r8342, reverted in r8372, committed in r8378,
and reverted in r8412.

COAUTHOR=henrik.lundin@webrtc.org
BUG=4228
TBR=henrik.lundin@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/34279004

Cr-Commit-Position: refs/heads/master@{#8433}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8433 4adac7df-926f-26a2-2b94-8c16560cd09d
5 files changed