Implement mapping blink track id to demuxer streams

media/base/mock_filters.h

Index: media/base/mock_filters.h
diff --git a/media/base/mock_filters.h b/media/base/mock_filters.h
index 78d18a5924847bf7188a7b91597fd4a749d401ae..0e2a11e325bb8020f0baf87d20a554f4a057ecff 100644
--- a/media/base/mock_filters.h
+++ b/media/base/mock_filters.h
@@ -19,6 +19,7 @@
 #include "media/base/decoder_buffer.h"
 #include "media/base/decryptor.h"
 #include "media/base/demuxer.h"
+#include "media/base/media_tracks.h"
 #include "media/base/pipeline.h"
 #include "media/base/pipeline_status.h"
 #include "media/base/renderer.h"
@@ -123,6 +124,10 @@ class MockDemuxer : public Demuxer {
   MOCK_CONST_METHOD0(GetTimelineOffset, base::Time());
   MOCK_CONST_METHOD0(GetMemoryUsage, int64_t());
 
+  MOCK_METHOD2(OnTrackIdsAssigned,
+               void(const MediaTracks&, const std::vector<unsigned>&));
+  MOCK_CONST_METHOD1(GetDemuxerStreamByTrackId, const DemuxerStream*(unsigned));
+
  private:
   DISALLOW_COPY_AND_ASSIGN(MockDemuxer);
 };