Revert of MSE: Relax the 'media segment must begin with keyframe' requirement

media/filters/chunk_demuxer.h

Index: media/filters/chunk_demuxer.h
diff --git a/media/filters/chunk_demuxer.h b/media/filters/chunk_demuxer.h
index 2425412802433b131346c26518dd63ac0c62d4ef..6954793aa8a5ebcd204cba3ae9248a5a93d7101f 100644
--- a/media/filters/chunk_demuxer.h
+++ b/media/filters/chunk_demuxer.h
@@ -80,8 +80,8 @@
   size_t GetBufferedSize() const;
 
   // Signal to the stream that buffers handed in through subsequent calls to
-  // Append() belong to a coded frame group that starts at |start_timestamp|.
-  void OnStartOfCodedFrameGroup(DecodeTimestamp start_timestamp);
+  // Append() belong to a media segment that starts at |start_timestamp|.
+  void OnNewMediaSegment(DecodeTimestamp start_timestamp);
 
   // Called when midstream config updates occur.
   // Returns true if the new config is accepted.