Stop using ACM factory in VoiceEngine

The factory injection was introduces in order to facilitate switching
between ACM1 and ACM2. Now, ACM1 is being deprecated, and this switching
mechanism is no longer needed.

BUG=2996
R=henrika@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12259005

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@5954 4adac7df-926f-26a2-2b94-8c16560cd09d
2 files changed