fix: Fix audio language switching while using AirPlay (shaka-project#…

…3472)

When sending a video to an AirPlay target, such as an Apple TV or a TV
with AirPlay built in, it can become impossible to change from one
audio language, to a second audio language, then return to the first
audio language.

When enabling a new audio track, it is assumed that
all other tracks will be disabled. However, while sending media to the
AirPlay target, no tracks are automatically disabled. As a result, it
would become impossible to reselect certain audio tracks as the player
would keep playing an enabled track, even if it isn't the most recently
enabled track.

Closes shaka-project#3125

AUTHORS

@@ -59,6 +59,7 @@ Rostislav Hejduk <Ross-cz@users.noreply.github.com>
 SameGoal Inc. <*@samegoal.com>
 Sanborn Hilland <sanbornh@rogers.com>
 Sander Saares <sander@saares.eu>
+Swank Motion Pictures Inc. <*@swankmp.com>
 TalkTalk Plc <*@talktalkplc.com>
 Tatsiana Gelahova <tatsiana.gelahova@gmail.com>
 Tomas Tichy <mr.tichyt@gmail.com>

CONTRIBUTORS

@@ -33,6 +33,7 @@ Ashutosh Kumar Mukhiya <ashukm4@gmail.com>
 Benjamin Wallberg <me@bwallberg.com>
 Benjamin Wallberg <benjamin.wallberg@bonnierbroadcasting.com>
 Boris Cupac <borisrt2309@gmail.com>
+Brad Nadler <bnadler@swankmp.com>
 Bryan Huh <bhh1988@gmail.com>
 Chad Assareh <assareh@google.com>
 Chris Fillmore <fillmore.chris@gmail.com>

lib/player.js

@@ -5176,6 +5176,12 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
     // This will reset the "enabled" of other tracks to false.
     track.enabled = true;
 
+    // AirPlay does not reset the "enabled" of other tracks to false, so
+    // it must be changed by hand.
+    if (track.id !== currentTrack.id) {
+      currentTrack.enabled = false;
+    }
+
     const oldTrack =
       shaka.util.StreamUtils.html5AudioTrackToTrack(currentTrack);
     const newTrack =