Reason for revert: Breaks Chrome since its build files were not updated prior to file removal. Original issue's description: > - Remove AudioTrackRenderer. > - Remove AddChannel/RemoveChannel from AudioRenderer interface. > > BUG=webrtc:4690 > > Committed: https://crrev.com/1c0bb386b67835feb5934f503dddfe0912bce3ac > Cr-Commit-Position: refs/heads/master@{#10226} TBR=tommi@webrtc.org,solenberg@webrtc.org NOPRESUBMIT=true NOTREECHECKS=true NOTRY=true BUG=webrtc:4690 Review URL: https://codereview.webrtc.org/1393343003 Cr-Commit-Position: refs/heads/master@{#10228}