This renames the following (in alphabetical order, non-exhaustive):

AudioCaptureStream -> AudioCaptureTrack
AudioNodeStream -> AudioNodeTrack
AudioNodeExternalInputStream -> AudioNodeExternalInputTrack
DirectMediaStreamTrackListener -> DirectMediaTrackListener
MediaStream -> MediaTrack
  - Note that there's also dom::MediaTrack. Namespaces differentiate them.
MediaStreamGraph -> MediaTrackGraph
MediaStreamTrackListener -> MediaTrackListener
MSG -> MTG (in comments)
ProcessedMediaStream -> ProcessedMediaTrack
SharedDummyStream -> SharedDummyTrack
SourceMediaStream -> SourceMediaTrack
StreamTime -> TrackTime
TrackUnionStream -> ForwardedInputTrack
  - Because this no longer takes a union of anything, but only a single track
    as input.

Other minor classes, members and comments have been updated to reflect these
name changes.

Differential Revision: https://phabricator.services.mozilla.com/D46146

--HG--
rename : dom/media/AudioCaptureStream.cpp => dom/media/AudioCaptureTrack.cpp
rename : dom/media/AudioCaptureStream.h => dom/media/AudioCaptureTrack.h
rename : dom/media/TrackUnionStream.cpp => dom/media/ForwardedInputTrack.cpp
rename : dom/media/TrackUnionStream.h => dom/media/ForwardedInputTrack.h
rename : dom/media/MediaStreamGraph.cpp => dom/media/MediaTrackGraph.cpp
rename : dom/media/MediaStreamGraph.h => dom/media/MediaTrackGraph.h
rename : dom/media/MediaStreamGraphImpl.h => dom/media/MediaTrackGraphImpl.h
rename : dom/media/MediaStreamListener.cpp => dom/media/MediaTrackListener.cpp
rename : dom/media/MediaStreamListener.h => dom/media/MediaTrackListener.h
rename : dom/media/webaudio/AudioNodeExternalInputStream.cpp => dom/media/webaudio/AudioNodeExternalInputTrack.cpp
rename : dom/media/webaudio/AudioNodeExternalInputStream.h => dom/media/webaudio/AudioNodeExternalInputTrack.h
rename : dom/media/webaudio/AudioNodeStream.cpp => dom/media/webaudio/AudioNodeTrack.cpp
rename : dom/media/webaudio/AudioNodeStream.h => dom/media/webaudio/AudioNodeTrack.h
extra : moz-landing-system : lando