In particular, PlayoutStereoData and StartPlayingAudioFile. This also
eliminates the dependency on system_wrappers FileWrapper.
Bug: None
Change-Id: I61df1eea1ad5f5035e36c8229febbf3668808f65
Reviewed-on: https://webrtc-review.googlesource.com/28121
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Magnus Flodman <mflodman@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21038}