Update the WebMediaSourceClientImpl & ChunkDemuxer to received explicit end of stream cancellation.

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 56422003c5ce5c8f46d73d06bf494c6a9b000054..59831997a8f220824a81ffb406dc641ecdff9b42 100644
--- a/media/filters/chunk_demuxer.h
+++ b/media/filters/chunk_demuxer.h
@@ -124,8 +124,12 @@ class MEDIA_EXPORT ChunkDemuxer : public Demuxer {
   // middle of parsing a media segment.
   bool SetTimestampOffset(const std::string& id, base::TimeDelta offset);
 
-  // Signals an EndOfStream request.
-  void EndOfStream(PipelineStatus status);
+  // Called to signal changes in the "end of stream"
+  // state. UnmarkEndOfStream() must not be called if a matching
+  // MarkEndOfStream() has not come before it.
+  void MarkEndOfStream(PipelineStatus status);
+  void UnmarkEndOfStream();
+
   void Shutdown();
 
   void SetMemoryLimitsForTesting(int memory_limit);