Generate and assign media track ids in demuxers.

media/filters/chunk_demuxer.cc

Index: media/filters/chunk_demuxer.cc
diff --git a/media/filters/chunk_demuxer.cc b/media/filters/chunk_demuxer.cc
index 9b1bbd7fdaec9dae76d16d10455f03a10be56719..83711f12b7f663deea3b74c893864551d0a903d9 100644
--- a/media/filters/chunk_demuxer.cc
+++ b/media/filters/chunk_demuxer.cc
@@ -15,8 +15,10 @@
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/stl_util.h"
+#include "base/strings/string_number_conversions.h"
 #include "media/base/audio_decoder_config.h"
 #include "media/base/bind_to_current_loop.h"
+#include "media/base/media_tracks.h"
 #include "media/base/stream_parser_buffer.h"
 #include "media/base/timestamp_constants.h"
 #include "media/base/video_decoder_config.h"
@@ -28,13 +30,14 @@ using base::TimeDelta;
 namespace media {
 
 ChunkDemuxerStream::ChunkDemuxerStream(Type type,
-                                       bool splice_frames_enabled)
+                                       bool splice_frames_enabled,
+                                       MediaTrack::Id media_track_id)
     : type_(type),
       liveness_(DemuxerStream::LIVENESS_UNKNOWN),
+      media_track_id_(media_track_id),
       state_(UNINITIALIZED),
       splice_frames_enabled_(splice_frames_enabled),
-      partial_append_window_trimming_enabled_(false) {
-}
+      partial_append_window_trimming_enabled_(false) {}
 
 void ChunkDemuxerStream::StartReturningData() {
   DVLOG(1) << "ChunkDemuxerStream::StartReturningData()";
@@ -1003,26 +1006,39 @@ void ChunkDemuxer::OnSourceInitDone(
   base::ResetAndReturn(&init_cb_).Run(PIPELINE_OK);
 }
 
+// static
+MediaTrack::Id ChunkDemuxer::GenerateMediaTrackId() {
+  static unsigned g_track_count = 0;
+  return base::UintToString(++g_track_count);
+}
+
 ChunkDemuxerStream* ChunkDemuxer::CreateDemuxerStream(
     DemuxerStream::Type type) {
+  // New ChunkDemuxerStreams can be created only during initialization segment
+  // processing, which happens when a new chunk of data is appended and the
+  // lock_ must be held by ChunkDemuxer::AppendData.
+  lock_.AssertAcquired();
+
+  MediaTrack::Id media_track_id = GenerateMediaTrackId();
+
   switch (type) {
     case DemuxerStream::AUDIO:
       if (audio_)
         return NULL;
-      audio_.reset(
-          new ChunkDemuxerStream(DemuxerStream::AUDIO, splice_frames_enabled_));
+      audio_.reset(new ChunkDemuxerStream(
+          DemuxerStream::AUDIO, splice_frames_enabled_, media_track_id));
       return audio_.get();
       break;
     case DemuxerStream::VIDEO:
       if (video_)
         return NULL;
-      video_.reset(
-          new ChunkDemuxerStream(DemuxerStream::VIDEO, splice_frames_enabled_));
+      video_.reset(new ChunkDemuxerStream(
+          DemuxerStream::VIDEO, splice_frames_enabled_, media_track_id));
       return video_.get();
       break;
     case DemuxerStream::TEXT: {
-      return new ChunkDemuxerStream(DemuxerStream::TEXT,
-                                    splice_frames_enabled_);
+      return new ChunkDemuxerStream(DemuxerStream::TEXT, splice_frames_enabled_,
+                                    media_track_id);
       break;
     }
     case DemuxerStream::UNKNOWN: