Update currentTextLanguage and currentAudioLanguage on track change.

We've been asked to implement this to allow for a custom app
behavior where app exposes all the tracks independent of language
and role.
In that scenario changing audio language will affect current text
track and the other way around. This CL makes sure it doesn't.

Closes #1299.

Change-Id: I39a9748c033ea748173ca00bfa7168dff642a03e

lib/player.js

@@ -1267,6 +1267,11 @@ shaka.Player.prototype.selectTextTrack = function(track) {
   // Add entries to the history.
   this.addTextStreamToSwitchHistory_(stream, /* fromAdaptation */ false);
   this.switchTextStream_(stream);
+
+  // Workaround for https://github.com/google/shaka-player/issues/1299
+  // When track is selected, back-propogate the language to
+  // currentTextLanguage_.
+  this.currentTextLanguage_ = stream.language;
 };
 
 
@@ -1340,6 +1345,11 @@ shaka.Player.prototype.selectVariantTrack = function(track, opt_clearBuffer) {
   // Add entries to the history.
   this.addVariantToSwitchHistory_(variant, /* fromAdaptation */ false);
   this.switchVariant_(variant, opt_clearBuffer);
+
+  // Workaround for https://github.com/google/shaka-player/issues/1299
+  // When track is selected, back-propogate the language to
+  // currentAudioLanguage_.
+  this.currentAudioLanguage_ = variant.language;
 };
 
 
@@ -1480,6 +1490,8 @@ shaka.Player.prototype.selectAudioLanguage =
   let period = this.streamingEngine_.getCurrentPeriod();
   this.currentAudioLanguage_ = language;
   this.currentVariantRole_ = opt_role || '';
+  // TODO: refactor to only change audio and not affect
+  // text.
   this.chooseStreamsAndSwitch_(period);
 };
 
@@ -1498,6 +1510,8 @@ shaka.Player.prototype.selectTextLanguage =
   let period = this.streamingEngine_.getCurrentPeriod();
   this.currentTextLanguage_ = language;
   this.currentTextRole_ = opt_role || '';
+  // TODO: refactor to only change text and not affect
+  // audio.
   this.chooseStreamsAndSwitch_(period);
 };
 

test/player_unit.js

@@ -1507,6 +1507,34 @@ describe('Player', function() {
           expect(getActiveVariantTrack().roles[0]).toBe('commentary');
         });
 
+      it('selectAudioLanguage() does not change selected text track',
+        function() {
+          // This came up in a custom application that allows to select
+          // from all tracks regardless of selected language.
+          // We imitate this behavior by calling selectTextLanguage()
+          // with one language and then selecting a track in a different
+          // language.
+          player.selectTextLanguage('en');
+          expect(textTracks[0].language).toBe('es');
+          player.selectTextTrack(textTracks[0]);
+          player.selectAudioLanguage('es');
+          expect(getActiveTextTrack().id).toBe(textTracks[0].id);
+        });
+
+      it('selectTextLanguage() does not change selected variant track',
+        function() {
+          // This came up in a custom application that allows to select
+          // from all tracks regardless of selected language.
+          // We imitate this behavior by calling selectAudioLanguage()
+          // with one language and then selecting a track in a different
+          // language.
+          player.selectAudioLanguage('es');
+          expect(variantTracks[0].language).toBe('en');
+          player.selectVariantTrack(variantTracks[0]);
+          player.selectTextLanguage('es');
+          expect(getActiveVariantTrack().id).toBe(variantTracks[0].id);
+        });
+
     it('selectTextLanguage() takes precedence over ' +
        'preferredTextLanguage', function() {
           streamingEngine.onCanSwitch();