Add live mode detection in WebM MediaSource parser.

media/base/stream_parser.h

Index: media/base/stream_parser.h
diff --git a/media/base/stream_parser.h b/media/base/stream_parser.h
index 5c088eb987647ce72e1adddb64662132840d0193..398e8e0a1af140eb2643fe0b5c30e3b2b992c6d4 100644
--- a/media/base/stream_parser.h
+++ b/media/base/stream_parser.h
@@ -60,6 +60,9 @@ class MEDIA_EXPORT StreamParser {
     // Indicates that timestampOffset should be updated based on the earliest
     // end timestamp (audio or video) provided during each NewBuffersCB.
     bool auto_update_timestamp_offset;
+
+    // Indicates live stream.
+    Demuxer::Liveness liveness;
   };
 
   // Indicates completion of parser initialization.