Use base::TickClock in media::AudioRendererImpl instead of a callback.

media/filters/audio_renderer_impl.h

Index: media/filters/audio_renderer_impl.h
diff --git a/media/filters/audio_renderer_impl.h b/media/filters/audio_renderer_impl.h
index 2e29a9e82110adce8bccd546adcb3992a1323247..cc06fa3bf58151d6225a770f4b270bf879802000 100644
--- a/media/filters/audio_renderer_impl.h
+++ b/media/filters/audio_renderer_impl.h
@@ -80,12 +80,6 @@ class MEDIA_EXPORT AudioRendererImpl
   virtual void StartPlayingFrom(base::TimeDelta timestamp) OVERRIDE;
   virtual void SetVolume(float volume) OVERRIDE;
 
-  // Allows injection of a custom time callback for non-realtime testing.
-  typedef base::Callback<base::TimeTicks()> NowCB;
-  void set_now_cb_for_testing(const NowCB& now_cb) {
-    now_cb_ = now_cb;
-  }
-
  private:
   friend class AudioRendererImplTest;
 
@@ -221,9 +215,6 @@ class MEDIA_EXPORT AudioRendererImpl
   // Callback provided to Flush().
   base::Closure flush_cb_;
 
-  // Typically calls base::TimeTicks::Now() but can be overridden by a test.
-  NowCB now_cb_;
-
   // After Initialize() has completed, all variables below must be accessed
   // under |lock_|. ------------------------------------------------------------
   base::Lock lock_;