MPRIS2 TrackList interface is claimed but missing

According to author kdekorte, http://kdekorte.blogspot.co.uk/2012/05/mpris2-support-in-gnome-mplayer.html, gnome-mplayer supports the MPRIS2 remote control interface since 1.0.7. This interface is useful eg to implement vendor-specific media player keys.

MPRIS2 comprises 4 interfaces, http://specifications.freedesktop.org/mpris-spec/latest/:

    org.mpris.MediaPlayer2
    org.mpris.MediaPlayer2.Player
optionally
    org.mpris.MediaPlayer2.TrackList
optionally
    org.mpris.MediaPlayer2.Playlists

In the version under test (Lubuntu 14.04, gnome-mplayer 1.0.8) the 2 required interfaces are supported. The HasTracklist property of interface org.mpris.MediaPlayer2 is returned as True. This means that the interface org.mpris.MediaPlayer2.TrackList ought to be supported, but it isn't, as shown in this output from a command-line MPRIS2 client.

Traceback (most recent call last):
  File "./mpris2-remote", line 749, in <module>
    for chunk in output_generator:
  File "./mpris2-remote", line 422, in trackinfo
    self.tracklist.GetTracksMetadata(['/org/mpris/MediaPlayer2/TrackList/' + track])
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 145, in __call__
    **keywords)
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 651, in call_blocking
    message, timeout)
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.UnknownMethod: Method "GetTracksMetadata" with signature "ao" on interface "org.mpris.MediaPlayer2.TrackList" doesn't exist

On checking the source file https://code.google.com/p/gnome-mplayer/source/browse/trunk/src/mpris-interface.c (r2452, latest), it becomes clear that the implementation of org.mpris.MediaPlayer2.TrackList is missing.

Consequently line 421 of the above file must be changed to, eg
                    b_val = FALSE; // change this to TRUE if the Tracklist interface is ever implemented

Then, and better, the Tracklist interface should be implemented.