Forward callback invocations to MediaLibrarySessionImpl

This is required for correct subscription notifications, as per the
referenced bug. It also just seems better to plumb things this way
in general, rather than re-implementing the functionality in the stub.

PiperOrigin-RevId: 413963824

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

@@ -97,12 +97,7 @@ import java.util.concurrent.atomic.AtomicReference;
     postOrRun(
         librarySessionImpl.getApplicationHandler(),
         () -> {
-          futureReference.set(
-              checkNotNull(
-                  librarySessionImpl
-                      .getCallback()
-                      .onGetLibraryRoot(librarySessionImpl.getInstance(), controller, params),
-                  "onGetLibraryRoot must return non-null future"));
+          futureReference.set(librarySessionImpl.onGetLibraryRootOnHandler(controller, params));
           haveFuture.open();
         });
     @Nullable LibraryResult<MediaItem> result = null;
@@ -143,10 +138,7 @@ import java.util.concurrent.atomic.AtomicReference;
           @Nullable
           LibraryParams params =
               MediaUtils.convertToLibraryParams(librarySessionImpl.getContext(), option);
-          ignoreFuture(
-              librarySessionImpl
-                  .getCallback()
-                  .onSubscribe(librarySessionImpl.getInstance(), controller, id, params));
+          ignoreFuture(librarySessionImpl.onSubscribeOnHandler(controller, id, params));
         });
   }
 
@@ -168,10 +160,7 @@ import java.util.concurrent.atomic.AtomicReference;
                   controller, SessionCommand.COMMAND_CODE_LIBRARY_UNSUBSCRIBE)) {
             return;
           }
-          ignoreFuture(
-              librarySessionImpl
-                  .getCallback()
-                  .onUnsubscribe(librarySessionImpl.getInstance(), controller, id));
+          ignoreFuture(librarySessionImpl.onUnsubscribeOnHandler(controller, id));
         });
   }
 
@@ -216,17 +205,8 @@ import java.util.concurrent.atomic.AtomicReference;
                 LibraryParams params =
                     MediaUtils.convertToLibraryParams(librarySessionImpl.getContext(), options);
                 ListenableFuture<LibraryResult<ImmutableList<MediaItem>>> future =
-                    checkNotNull(
-                        librarySessionImpl
-                            .getCallback()
-                            .onGetChildren(
-                                librarySessionImpl.getInstance(),
-                                controller,
-                                parentId,
-                                page,
-                                pageSize,
-                                params),
-                        "onGetChildren must return non-null future");
+                    librarySessionImpl.onGetChildrenOnHandler(
+                        controller, parentId, page, pageSize, params);
                 sendLibraryResultWithMediaItemsWhenReady(result, future);
                 return;
               }
@@ -239,17 +219,12 @@ import java.util.concurrent.atomic.AtomicReference;
           }
           // A MediaBrowserCompat called loadChildren with no pagination option.
           ListenableFuture<LibraryResult<ImmutableList<MediaItem>>> future =
-              checkNotNull(
-                  librarySessionImpl
-                      .getCallback()
-                      .onGetChildren(
-                          librarySessionImpl.getInstance(),
-                          controller,
-                          parentId,
-                          /* page= */ 0,
-                          /* pageSize= */ Integer.MAX_VALUE,
-                          /* extras= */ null),
-                  "onGetChildren must return non-null future");
+              librarySessionImpl.onGetChildrenOnHandler(
+                  controller,
+                  parentId,
+                  /* page= */ 0,
+                  /* pageSize= */ Integer.MAX_VALUE,
+                  /* extras= */ null);
           sendLibraryResultWithMediaItemsWhenReady(result, future);
         });
   }
@@ -277,11 +252,7 @@ import java.util.concurrent.atomic.AtomicReference;
             return;
           }
           ListenableFuture<LibraryResult<MediaItem>> future =
-              checkNotNull(
-                  librarySessionImpl
-                      .getCallback()
-                      .onGetItem(librarySessionImpl.getInstance(), controller, itemId),
-                  "onGetItem must return non-null future");
+              librarySessionImpl.onGetItemOnHandler(controller, itemId);
           sendLibraryResultWithMediaItemWhenReady(result, future);
         });
   }
@@ -316,10 +287,7 @@ import java.util.concurrent.atomic.AtomicReference;
           @Nullable
           LibraryParams params =
               MediaUtils.convertToLibraryParams(librarySessionImpl.getContext(), extras);
-          ignoreFuture(
-              librarySessionImpl
-                  .getCallback()
-                  .onSearch(librarySessionImpl.getInstance(), controller, query, params));
+          ignoreFuture(librarySessionImpl.onSearchOnHandler(controller, query, params));
           // Actual search result will be sent by notifySearchResultChanged().
         });
   }
@@ -526,17 +494,8 @@ import java.util.concurrent.atomic.AtomicReference;
                   MediaUtils.convertToLibraryParams(
                       librarySessionImpl.getContext(), request.extras);
               ListenableFuture<LibraryResult<ImmutableList<MediaItem>>> future =
-                  checkNotNull(
-                      librarySessionImpl
-                          .getCallback()
-                          .onGetSearchResult(
-                              librarySessionImpl.getInstance(),
-                              request.controller,
-                              request.query,
-                              page,
-                              pageSize,
-                              libraryParams),
-                      "onGetSearchResult must return non-null future");
+                  librarySessionImpl.onGetSearchResultOnHandler(
+                      request.controller, request.query, page, pageSize, libraryParams);
               sendLibraryResultWithMediaItemsWhenReady(request.result, future);
             }
           });