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

media/base/pipeline_impl.h

Index: media/base/pipeline_impl.h
diff --git a/media/base/pipeline_impl.h b/media/base/pipeline_impl.h
index 7b5fe4a6c2dbd3fde22fe730e1674a9ad0e306b5..caf4e19f081709a4ace1b08c822a850e970136eb 100644
--- a/media/base/pipeline_impl.h
+++ b/media/base/pipeline_impl.h
@@ -205,10 +205,12 @@ class PipelineImpl : public Pipeline, public FilterHost {
   // Callback executed by filters upon completing initialization.
   void OnFilterInitialize();
 
-  // Callback executed by filters upon completing Play(), Pause(), Seek(),
-  // or Stop().
+  // Callback executed by filters upon completing Play(), Pause(), or Stop().
   void OnFilterStateTransition();
 
+  // Callback executed by filters upon completing Seek().
+  void OnFilterStateTransitionWithStatus(PipelineStatus status);
+
   // Callback executed by filters when completing teardown operations.
   void OnTeardownStateTransition();