If a playbackPreparer is set, then instead of calling `player.prepare()`, the MediaSessionConnector will call `playbackPreparer.onPrepare(true)` instead, as seen below.
This commit makes it so that playbackPreparer.onPrepare(true) restores the original behavior of just calling player.prepare().
From MediaSessionConnector -> MediaSessionCompat.Callback implementation:
```java
@Override
public void onPlay() {
if (canDispatchPlaybackAction(PlaybackStateCompat.ACTION_PLAY)) {
if (player.getPlaybackState() == Player.STATE_IDLE) {
if (playbackPreparer != null) {
playbackPreparer.onPrepare(/* playWhenReady= */ true);
} else {
player.prepare();
}
} else if (player.getPlaybackState() == Player.STATE_ENDED) {
seekTo(player, player.getCurrentMediaItemIndex(), C.TIME_UNSET);
}
Assertions.checkNotNull(player).play();
}
}
```
ec6612dd71