[Video] Collect average keyframe distance for video

media/filters/decoder_stream_traits.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_FILTERS_DECODER_STREAM_TRAITS_H_
 #define MEDIA_FILTERS_DECODER_STREAM_TRAITS_H_
 
+#include "base/time/time.h"
 #include "media/base/cdm_context.h"
 #include "media/base/demuxer_stream.h"
 #include "media/base/pipeline_status.h"
 #include "media/base/video_decoder_config.h"
 #include "media/filters/audio_timestamp_validator.h"
 
 namespace media {
 
 class AudioBuffer;
 class AudioDecoder;
@@ skipping 57 matching lines @@
                                int bytes_decoded);
   static scoped_refptr<OutputType> CreateEOSOutput();
 
   explicit DecoderStreamTraits(const scoped_refptr<MediaLog>& media_log) {}
 
   void InitializeDecoder(DecoderType* decoder,
                          DemuxerStream* stream,
                          CdmContext* cdm_context,
                          const InitCB& init_cb,
                          const OutputCB& output_cb);
-  void OnDecode(const scoped_refptr<DecoderBuffer>& buffer) {}
+  void OnDecode(const scoped_refptr<DecoderBuffer>& buffer);
   void OnDecodeDone(const scoped_refptr<OutputType>& buffer) {}
-  void OnStreamReset(DemuxerStream* stream) {}
+  void OnStreamReset(DemuxerStream* stream);
+
+ private:
+  base::TimeDelta last_keyframe_timestamp_;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_DECODER_STREAM_TRAITS_H_