Correct Event Dispatch When Text Track Is Selected
Correct Event Dispatch When Text Track Is Selected

This change corrects which event we dispatch when selecting
text tracks.

According to our documentation, we are suppose to dispatch
the |textchanged| event when we select a text track, but we
were dispatching |trackschanged|.

Change-Id: Ice0ea02122f07db7920244e4a4c112afd10993d8

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