This change is for Android 12 and below, where the buttons are derived from the actions added with the notification. From Android 13 (https://developer.android.com/about/versions/13/behavior-changes-13#playback-controls), the system derives media controls from `PlaybackState` actions.
When adding the actions onto the notification, the logic will iterate all the command buttons. The `COMMAND_KEY_CONPACT_VIEW_INDEX` extra will be checked for each button. If that extra is set for the three buttons on the compact view, then the customized buttons and their order will be used. Otherwise, the compact view will be "seekPrev" (if any), "play/pause" (if any), "seekNext" (if any) buttons (in such order).
Issue: androidx/media#410
PiperOrigin-RevId: 538797874
2e2f19351f