This CL opens up support for DTMF tones to be played to multi-channel outputs. The same tones are replicated across all channels. Unit tests are updated. Also adding a new method AudioMultiVector::CopyChannel. BUG=crbug/407114 R=tina.legrand@webrtc.org Review URL: https://webrtc-codereview.appspot.com/20279004 git-svn-id: http://webrtc.googlecode.com/svn/trunk@7056 4adac7df-926f-26a2-2b94-8c16560cd09d