don't clear display

Author: gkatsev

src/js/tracks/text-track-display.js

@@ -243,7 +243,7 @@ class TextTrackDisplay extends Component {
     const tracks = this.player_.textTracks();
     const allowMultipleShowingTracks = this.options_.allowMultipleShowingTracks;
 
-    this.clearDisplay();
+    // this.clearDisplay();
 
     if (allowMultipleShowingTracks) {
       const showingTracks = [];