CL also replaces deprecated AudioSession calls with equivalent AVAudioSession ones. BUG=3487 R=glaznev@webrtc.org, noahric@chromium.org Review URL: https://webrtc-codereview.appspot.com/21769004 git-svn-id: http://webrtc.googlecode.com/svn/trunk@6697 4adac7df-926f-26a2-2b94-8c16560cd09d