Convert Filter::Seek() to use new callback system.

media/filters/audio_renderer_base.h

Index: media/filters/audio_renderer_base.h
diff --git a/media/filters/audio_renderer_base.h b/media/filters/audio_renderer_base.h
index 0b13e02aecf725b34ac9ca05121e4e36e54f0a5c..18827430307f3b5fd27a0e76af5b0a038ca08af6 100644
--- a/media/filters/audio_renderer_base.h
+++ b/media/filters/audio_renderer_base.h
@@ -37,7 +37,7 @@ class AudioRendererBase : public AudioRenderer {
   virtual void Pause(FilterCallback* callback);
   virtual void Stop(FilterCallback* callback);
 
-  virtual void Seek(base::TimeDelta time, FilterCallback* callback);
+  virtual void Seek(base::TimeDelta time, const FilterStatusCB& cb);
 
   // AudioRenderer implementation.
   virtual void Initialize(AudioDecoder* decoder, FilterCallback* callback);
@@ -125,7 +125,7 @@ class AudioRendererBase : public AudioRenderer {
 
   // Filter callbacks.
   scoped_ptr<FilterCallback> pause_callback_;
-  scoped_ptr<FilterCallback> seek_callback_;
+  FilterStatusCB seek_cb_;
 
   base::TimeDelta seek_timestamp_;