Always create media source for external text.

We used to only create media source for external text
when captions are turned on. It created problems with combining
external text with native controls. Native captions button changes
the state of a text track (unlike our button, which also triggers
media source creation if needed), but because there is no media source for
text, we had nothing to display.

Fixes #1596.

Change-Id: Ifeca9bf987f78061d77ccbc89bf94066061ebd74

lib/media/streaming_engine.js

@@ -520,11 +520,10 @@ shaka.media.StreamingEngine.prototype.getStream_ = function(type) {
  * the stream has been set up, and a media state has been created.
  *
  * @param {shaka.extern.Stream} stream
- * @param {boolean} createMediaState
  * @return {!Promise}
  */
 shaka.media.StreamingEngine.prototype.loadNewTextStream = async function(
-    stream, createMediaState) {
+    stream) {
   const ContentType = shaka.util.ManifestParserUtils.ContentType;
 
   // Clear MediaSource's buffered text, so that the new text stream will
@@ -553,8 +552,7 @@ shaka.media.StreamingEngine.prototype.loadNewTextStream = async function(
   await this.setupStreams_(streamSet);
   if (this.destroyed_) { return; }
 
-  if (createMediaState &&
-      (this.textStreamSequenceId_ == currentSequenceId) &&
+  if ((this.textStreamSequenceId_ == currentSequenceId) &&
       !this.mediaStates_.has(ContentType.TEXT) &&
       !this.unloadingTextStream_) {
     let playheadTime = this.playerInterface_.playhead.getTime();
@@ -660,7 +658,7 @@ shaka.media.StreamingEngine.prototype.switchInternal_ = function(
 
   if (!mediaState && stream.type == ContentType.TEXT &&
       this.config_.ignoreTextStreamFailures) {
-    this.loadNewTextStream(stream, /* createMediaState */ true);
+    this.loadNewTextStream(stream);
     return;
   }
   goog.asserts.assert(mediaState, 'switch: expected mediaState to exist');

lib/player.js

@@ -1965,8 +1965,7 @@ shaka.Player.prototype.setTextTrackVisibility = function(on) {
         this.currentTextRole_);
     let stream = textStreams[0];
     if (stream) {
-      this.streamingEngine_.loadNewTextStream(
-        stream, /* createMediaState */ true);
+      this.streamingEngine_.loadNewTextStream(stream);
     }
   } else {
     this.streamingEngine_.unloadTextStream();
@@ -2171,9 +2170,9 @@ shaka.Player.prototype.addTextTrack = function(
   // is initializing.
   this.loadingTextStreamIds_.push(stream.id);
   period.textStreams.push(stream);
-  // Don't create the media state until subtitles are actually enabled
-  return this.streamingEngine_.loadNewTextStream(
-      stream, this.textVisibility_).then(function() {
+
+  return this.streamingEngine_.loadNewTextStream(stream)
+          .then(function() {
     if (this.destroyer_.destroyed()) {
       return;
     }

test/media/streaming_engine_unit.js

@@ -631,8 +631,7 @@ describe('StreamingEngine', function() {
         if (playheadTime == 20) {
           mediaSourceEngine.clear.calls.reset();
           mediaSourceEngine.init.calls.reset();
-          streamingEngine.loadNewTextStream(textStream1,
-                                            /* createMediaState */ true);
+          streamingEngine.loadNewTextStream(textStream1);
           expect(mediaSourceEngine.clear).toHaveBeenCalledWith('text');
 
           const expectedObject = new Map();