Make VoiceEngine choose ACM2 by default

The use of a factory for ACM will be removed in later CLs.

BUG=2996
R=henrika@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12069004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@5923 4adac7df-926f-26a2-2b94-8c16560cd09d
1 file changed