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

media/base/filters.h

Index: media/base/filters.h
diff --git a/media/base/filters.h b/media/base/filters.h
index 901a91bc4f3950dc446f51880557150b6fe63b0c..cceed6759edb38df4f364829efedcbfe77478e82 100644
--- a/media/base/filters.h
+++ b/media/base/filters.h
@@ -33,6 +33,7 @@
 #include "base/time.h"
 #include "media/base/audio_decoder_config.h"
 #include "media/base/media_format.h"
+#include "media/base/pipeline_status.h"
 #include "media/base/video_frame.h"
 
 struct AVStream;
@@ -62,6 +63,12 @@ enum Preload {
 
 // Used for completing asynchronous methods.
 typedef Callback0::Type FilterCallback;
+typedef base::Callback<void(PipelineStatus)> FilterStatusCB;
+
+// This function copies |cb|, calls Reset() on |cb|, and then calls Run()
+// on the copy. This is used in the common case where you need to clear
+// a callback member variable before running the callback.
+void ResetAndRunCB(FilterStatusCB* cb, PipelineStatus status);
 
 // Used for updating pipeline statistics.
 typedef Callback1<const PipelineStatistics&>::Type StatisticsCallback;
@@ -104,7 +111,7 @@ class Filter : public base::RefCountedThreadSafe<Filter> {
 
   // Carry out any actions required to seek to the given time, executing the
   // callback upon completion.
-  virtual void Seek(base::TimeDelta time, FilterCallback* callback);
+  virtual void Seek(base::TimeDelta time, const FilterStatusCB& callback);
 
   // This method is called from the pipeline when the audio renderer
   // is disabled. Filters can ignore the notification if they do not