Anti-drift in RCC playback position

Periodically verify that the reported playback position hasn't
 drifted from the estimated playback position.
If a drift is noticed, re-synchronize registered
 IRemoteControlDisplay implementations.

bug 8120740

Note that this implementation updates the playback position
 of  all IRemoteControlDisplay implementations,
 and always causes the OnGetPlaybackPositionListener to be
 called. This might be undesirable in some circumstances
 and will be addressed in a subsequent CL.

Change-Id: Ib9f40e1b000e912f6c35fa03e41adf81efadc894