Introduce the playback time into the MSE garbage collection.

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 f19a3d4f557fc33026962019f186122ac06a27f3..ddc1f1c53bd29f76178f91902bd20522e4efa933 100644
--- a/media/filters/chunk_demuxer.h
+++ b/media/filters/chunk_demuxer.h
@@ -43,7 +43,8 @@ class MEDIA_EXPORT ChunkDemuxerStream : public DemuxerStream {
   // Add buffers to this stream.  Buffers are stored in SourceBufferStreams,
   // which handle ordering and overlap resolution.
   // Returns true if buffers were successfully added.
-  bool Append(const StreamParser::BufferQueue& buffers);
+  bool Append(const StreamParser::BufferQueue& buffers,
+              base::TimeDelta media_time);
 
   // Removes buffers between |start| and |end| according to the steps
   // in the "Coded Frame Removal Algorithm" in the Media Source
@@ -367,6 +368,10 @@ class MEDIA_EXPORT ChunkDemuxer : public Demuxer {
 
   base::TimeDelta duration_;
 
+  // Current media time used to prevent garbage collecting buffers
+  // between the media time and the source buffer read position.
+  base::TimeDelta media_time_;
+
   // The duration passed to the last SetDuration(). If
   // SetDuration() is never called or an AppendData() call or
   // a EndOfStream() call changes |duration_|, then this