Add change event to audiotracks and texttracks (#2134)
Add change event to audiotracks and texttracks (#2134)


shaka-project/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,tvoli/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,tvoli/shaka-player