Change default of throwsWhenUsingWrongThread to true

Apps can still opt out for now, but this option will be removed in
the future.

Issue: #4463
PiperOrigin-RevId: 333489424

RELEASENOTES.md

@@ -6,6 +6,10 @@
     *   Fix bug where streams with highly uneven durations may get stuck in a
         buffering state
         ([#7943](https://github.com/google/ExoPlayer/issues/7943)).
+    *   Verify correct thread usage in `SimpleExoPlayer` by default. Opt-out is
+        still possible until the next major release using
+        `setThrowsWhenUsingWrongThread(false)`
+        ([#4463](https://github.com/google/ExoPlayer/issues/4463)).
 *   Track selection:
     *   Add option to specify multiple preferred audio or text languages.
 *   Data sources:

library/core/src/main/java/com/google/android/exoplayer2/SimpleExoPlayer.java

@@ -618,6 +618,7 @@ public class SimpleExoPlayer extends BasePlayer
     audioVolume = 1;
     audioSessionId = C.AUDIO_SESSION_ID_UNSET;
     currentCues = Collections.emptyList();
+    throwsWhenUsingWrongThread = true;
 
     // Build the player and associated objects.
     player =
@@ -1948,7 +1949,7 @@ public class SimpleExoPlayer extends BasePlayer
    * Sets whether the player should throw an {@link IllegalStateException} when methods are called
    * from a thread other than the one associated with {@link #getApplicationLooper()}.
    *
-   * <p>The default is {@code false}, but will change to {@code true} in the future.
+   * <p>The default is {@code true} and this method will be removed in the future.
    *
    * @param throwsWhenUsingWrongThread Whether to throw when methods are called from a wrong thread.
    */