Revert of Switch to using media::TimeSource inside media::RendererImpl.

media/base/wall_clock_time_source.cc

Index: media/base/wall_clock_time_source.cc
diff --git a/media/base/wall_clock_time_source.cc b/media/base/wall_clock_time_source.cc
index f7a8f6ef894d843ba9dd67dc46013ffbc822ce2d..67b16f717952c29dc1d8e7fe5abb174a0ec60bef 100644
--- a/media/base/wall_clock_time_source.cc
+++ b/media/base/wall_clock_time_source.cc
@@ -57,10 +57,6 @@
              (now - reference_wall_ticks_).InMicroseconds() * playback_rate_);
 }
 
-base::TimeDelta WallClockTimeSource::CurrentMediaTimeForSyncingVideo() {
-  return CurrentMediaTime();
-}
-
 void WallClockTimeSource::SetTickClockForTesting(
     scoped_ptr<base::TickClock> tick_clock) {
   tick_clock_.swap(tick_clock);