Fixes in management of the video size check timer of TextTracks
Created by: epiclabsDASH
Fix for issue #2182 (closed).
Due to the way the videoSizeCheck timer was created, we couldn't be 100% sure checkVideoSize was working with the selected text track. With these changes, timer is now started when the selected text track is html based and we are restarting it whenever a text track change is requested.