Add exception cause to thrown exception

PiperOrigin-RevId: 509473556
(cherry picked from commit 56803bf)

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/offline/DefaultDownloaderFactory.java

@@ -105,7 +105,7 @@ private Downloader createDownloader(DownloadRequest request, @C.ContentType int
       return constructor.newInstance(mediaItem, cacheDataSourceFactory, executor);
     } catch (Exception e) {
       throw new IllegalStateException(
-          "Failed to instantiate downloader for content type " + contentType);
+          "Failed to instantiate downloader for content type " + contentType, e);
     }
   }