don't require SwapChain to be passed to viewer.render - this will just render into all registered swapchains

thermion_dart/test/render_thread_tests.dart

@@ -13,20 +13,11 @@ void main() async {
   test("request frame on render thread", () async {
     await testHelper.withViewer((viewer) async {
       await viewer.render();
-
-      await Future.delayed(Duration(milliseconds: 1));
-
-      // var data = viewer.metalTexture.getTextureBytes()!;
-      // var pixels = data.bytes.cast<Uint8>().asTypedList(data.length);
-
-      // savePixelBufferToBmp(
-      //     pixels, 500, 500, "${testHelper.testDir}/request_frame.bmp");
-
+      await Future.delayed(Duration(seconds: 1));
       await viewer.setRendering(true);
-
       await Future.delayed(Duration(seconds: 1));
       await FilamentApp.instance!.requestFrame();
       await testHelper.capture(viewer.view, "render_thread_2");
-    });
+    }, addSkybox: true);
   });
 }