Do not require package visibility when obtaining SessionTokens

The only reason this is required at the moment is to set the
process UID field in the token, that is supposed to make it easier
for controller apps to identify the session. However, if this
visibility is not provided, it shouldn't stop us from creating
the controller for this session.

Also docuement more clearly what UID means in this context.

PiperOrigin-RevId: 490184508
(cherry picked from commit c41a5c84)

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

@@ -36,6 +36,7 @@ import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
 import androidx.annotation.Nullable;
 import androidx.media.MediaBrowserServiceCompat;
 import androidx.media.MediaBrowserServiceCompat;
 import androidx.media3.common.Bundleable;
 import androidx.media3.common.Bundleable;
+import androidx.media3.common.C;
 import androidx.media3.common.MediaLibraryInfo;
 import androidx.media3.common.MediaLibraryInfo;
 import androidx.media3.common.util.UnstableApi;
 import androidx.media3.common.util.UnstableApi;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.ImmutableSet;
@@ -179,7 +180,11 @@ public final class SessionToken implements Bundleable {
     return impl.toString();
     return impl.toString();
   }
   }
 
 
-  /** Returns the uid of the session */
+  /**
+   * Returns the UID of the session process, or {@link C#INDEX_UNSET} if the UID can't be determined
+   * due to missing <a href="https://developer.android.com/training/package-visibility">package
+   * visibility</a>.
+   */
   public int getUid() {
   public int getUid() {
     return impl.getUid();
     return impl.getUid();
   }
   }
@@ -393,8 +398,7 @@ public final class SessionToken implements Bundleable {
     try {
     try {
       return manager.getApplicationInfo(packageName, 0).uid;
       return manager.getApplicationInfo(packageName, 0).uid;
     } catch (PackageManager.NameNotFoundException e) {
     } catch (PackageManager.NameNotFoundException e) {
-      throw new IllegalArgumentException(
-          "Cannot find package " + packageName + " or package is not visible", e);
+      return C.INDEX_UNSET;
     }
     }
   }
   }