Add live mode detection in WebM MediaSource parser.

media/formats/webm/webm_stream_parser.cc

Index: media/formats/webm/webm_stream_parser.cc
diff --git a/media/formats/webm/webm_stream_parser.cc b/media/formats/webm/webm_stream_parser.cc
index d477f0bb83fe503d0bd740f49d584afa861620d1..3a4ada04a2b3a0946acf93f6dc6cfb281508a635 100644
--- a/media/formats/webm/webm_stream_parser.cc
+++ b/media/formats/webm/webm_stream_parser.cc
@@ -20,6 +20,7 @@ namespace media {
 
 WebMStreamParser::WebMStreamParser()
     : state_(kWaitingForInit),
+      unknown_segment_size_(false),
       parsing_cluster_(false) {
 }
 
@@ -150,6 +151,9 @@ int WebMStreamParser::ParseInfoAndTracks(const uint8* data, int size) {
       return result + element_size;
       break;
     case kWebMIdSegment:
+      // Segment of unknown size indicates live stream.
+      if (element_size == kWebMUnknownSize)
+        unknown_segment_size_ = true;
       // Just consume the segment header.
       return result;
       break;
@@ -190,6 +194,9 @@ int WebMStreamParser::ParseInfoAndTracks(const uint8* data, int size) {
 
   params.timeline_offset = info_parser.date_utc();
 
+  params.live_mode = unknown_segment_size_ && (info_parser.duration() <= 0) &&
+                     !info_parser.date_utc().is_null();
+
   const AudioDecoderConfig& audio_config = tracks_parser.audio_decoder_config();
   if (audio_config.is_encrypted())
     FireNeedKey(tracks_parser.audio_encryption_key_id());
@@ -205,7 +212,6 @@ int WebMStreamParser::ParseInfoAndTracks(const uint8* data, int size) {
     return -1;
   }
 
-
   cluster_parser_.reset(new WebMClusterParser(
       info_parser.timecode_scale(),
       tracks_parser.audio_track_num(),