Remove kVp9CodecId

Change-Id: I1b4926da0dad0e9a44e352c2b4428ce9e24cfa0c

third_party/libwebm/mkvmuxer.cpp

@@ -1046,7 +1046,6 @@ bool AudioTrack::Write(IMkvWriter* writer) const {
 const char Tracks::kOpusCodecId[] = "A_OPUS";
 const char Tracks::kVorbisCodecId[] = "A_VORBIS";
 const char Tracks::kAOMCodecId[] = "V_AOM";
-const char Tracks::kVp9CodecId[] = "V_AV1";
 const char Tracks::kAV1CodecId[] = "V_AV1";
 
 Tracks::Tracks() : track_entries_(NULL), track_entries_size_(0) {}

third_party/libwebm/mkvmuxer.hpp

@@ -536,7 +536,6 @@ class Tracks {
   static const char kOpusCodecId[];
   static const char kVorbisCodecId[];
   static const char kAOMCodecId[];
-  static const char kVp9CodecId[];
   static const char kAV1CodecId[];
 
   Tracks();