Strip down GStreamerBackend to bare minimum

mopidy/backends/gstreamer.py

@@ -1,10 +1,6 @@
 import logging
 
-import gst
-
-from mopidy import config
-from mopidy.backends import BaseBackend
-from mopidy.models import Artist, Album, Track, Playlist
+from mopidy.backends import BaseBackend, BasePlaybackController
 
 logger = logging.getLogger(u'backends.gstreamer')
 
@@ -12,30 +8,8 @@ class GStreamerBackend(BaseBackend):
     def __init__(self, *args, **kwargs):
         super(GStreamerBackend, self).__init__(*args, **kwargs)
 
-        playlist = []
-        player = gst.element_factory_make("playbin2", "player")
-        fakesink = gst.element_factory_make("fakesink", "fakesink")
+        self.playback = GStreamerPlaybackController(self)
 
-        player.set_property("video-sink", fakesink)
-
-        self.player = player
-
-    def _play(self):
-        if self._current_track is None:
-            return False
-
-        self.player.set_property("uri", self._current_track.uri)
-        self.player.set_state(gst.STATE_PLAYING)
-
-        return True
-
-    def _stop(self):
-        self.player.set_state(gst.STATE_NULL)
-
-        return True
-
-    def playlist_add_track(self, uri, pos=None):
-        tracks = self._current_playlist.tracks
-        tracks.insert(pos or -1, Track(uri))
-
-        self._current_playlist = Playlist(tracks=tracks)
+class GStreamerPlaybackController(BasePlaybackController):
+    def __init__(self, backend):
+        super(GStreamerPlaybackController, self).__init__(backend)