Merge pull request #1289 from vegasmurphy/textTrackPolling

Add textTrack polling for browsers that don't have textTrack onchange events

src/controller/subtitle-track-controller.js

@@ -60,15 +60,26 @@ class SubtitleTrackController extends EventHandler {
     }
 
     this.trackChangeListener = this._onTextTracksChanged.bind(this);
-    this.media.textTracks.addEventListener('change', this.trackChangeListener);
+
+    this.useTextTrackPolling = !(this.media.textTracks && 'onchange' in this.media.textTracks);
+    if (this.useTextTrackPolling) {
+      this.subtitlePollingInterval = setInterval(() => {
+        this.trackChangeListener();
+      }, 500);
+    } else {
+      this.media.textTracks.addEventListener('change', this.trackChangeListener);
+    }
   }
 
   onMediaDetaching() {
     if (!this.media) {
       return;
     }
-
-    this.media.textTracks.removeEventListener('change', this.trackChangeListener);
+    if (this.useTextTrackPolling) {
+      clearInterval(this.subtitlePollingInterval);
+    } else {
+      this.media.textTracks.removeEventListener('change', this.trackChangeListener);
+    }
 
     this.media = undefined;
   }