Ensure Media3 play calls get FGS exemption

When a Media3 controller calls play on a Media3 session, the call
is currently not routed through the platform session at all.
This means the usual exemption to start a FGS for media controller
interactions is not triggered.

We can manually ensure this exemption is given by sending a custom
platform command to the session. The Media3 session will never
receive this command as it's not a known Media3 custom command.
Sessions will see a single onConnect call with a platform controller
from the sender app though. We can prevent this on newer versions of
the code by dropping the onCommand call early.

PiperOrigin-RevId: 679115247

RELEASENOTES.md

@@ -94,6 +94,8 @@
         items are available for both, `MediaBrowser` and `MediaController`. See
         <a href="https://developer.android.com/training/cars/media#custom_browse_actions">Custom
         Browse actions of AAOS</a>.
+    *   Fix bug where a Media3 controller was sometimes unable to let a session
+        app start a foreground service after requesting `play()`.
 *   UI:
     *   Make the stretched/cropped video in
         `PlayerView`-in-Compose-`AndroidView` workaround opt-in, due to issues

libraries/session/src/main/java/androidx/media3/session/MediaConstants.java

@@ -497,6 +497,8 @@ public final class MediaConstants {
       "androidx.media3.session.SESSION_COMMAND_ON_CAPTIONING_ENABLED_CHANGED";
   /* package */ static final String SESSION_COMMAND_REQUEST_SESSION3_TOKEN =
       "androidx.media3.session.SESSION_COMMAND_REQUEST_SESSION3_TOKEN";
+  /* package */ static final String SESSION_COMMAND_MEDIA3_PLAY_REQUEST =
+      "androidx.media3.session.SESSION_COMMAND_MEDIA3_PLAY_REQUEST";
 
   /* package */ static final String ARGUMENT_CAPTIONING_ENABLED =
       "androidx.media3.session.ARGUMENT_CAPTIONING_ENABLED";

libraries/session/src/main/java/androidx/media3/session/MediaControllerImplBase.java

@@ -137,6 +137,7 @@ import org.checkerframework.checker.nullness.qual.NonNull;
   @Nullable private TextureView videoTextureView;
   private Size surfaceSize;
   @Nullable private IMediaSession iSession;
+  @Nullable private android.media.session.MediaController platformController;
   private long currentPositionMs;
   private long lastSetPlayWhenReadyCalledTimeMs;
   @Nullable private PlayerInfo pendingPlayerInfo;
@@ -405,6 +406,13 @@ import org.checkerframework.checker.nullness.qual.NonNull;
       return;
     }
 
+    if (Util.SDK_INT >= 31 && platformController != null) {
+      // Ensure the platform session gets allow-listed to start a foreground service after receiving
+      // the play command.
+      platformController.sendCommand(
+          MediaConstants.SESSION_COMMAND_MEDIA3_PLAY_REQUEST, /* args= */ null, /* cb= */ null);
+    }
+
     dispatchRemoteSessionTaskWithPlayerCommand(
         (iSession, seq) -> iSession.play(controllerStub, seq));
 
@@ -2644,6 +2652,9 @@ import org.checkerframework.checker.nullness.qual.NonNull;
     playerInfo = result.playerInfo;
     MediaSession.Token platformToken =
         result.platformToken == null ? token.getPlatformToken() : result.platformToken;
+    if (platformToken != null) {
+      platformController = new android.media.session.MediaController(context, platformToken);
+    }
     try {
       // Implementation for the local binder is no-op,
       // so can be used without worrying about deadlock.

libraries/session/src/main/java/androidx/media3/session/MediaSessionLegacyStub.java

@@ -280,8 +280,11 @@ import org.checkerframework.checker.initialization.qual.Initialized;
   @Override
   public void onCommand(String commandName, @Nullable Bundle args, @Nullable ResultReceiver cb) {
     checkStateNotNull(commandName);
-    if (TextUtils.equals(MediaConstants.SESSION_COMMAND_REQUEST_SESSION3_TOKEN, commandName)
+    if (commandName.equals(MediaConstants.SESSION_COMMAND_MEDIA3_PLAY_REQUEST)) {
-        && cb != null) {
+      // Ignore, no need to handle this command here.
+      return;
+    }
+    if (commandName.equals(MediaConstants.SESSION_COMMAND_REQUEST_SESSION3_TOKEN) && cb != null) {
       cb.send(RESULT_SUCCESS, sessionImpl.getToken().toBundle());
       return;
     }