Function create_constellation 

pub(crate) fn create_constellation(
    embedder_to_constellation_receiver: Receiver<EmbedderToConstellationMessage>,
    compositor: &IOCompositor,
    config_dir: Option<PathBuf>,
    embedder_proxy: EmbedderProxy,
    compositor_proxy: CompositorProxy,
    time_profiler_chan: ProfilerChan,
    mem_profiler_chan: ProfilerChan,
    devtools_sender: Option<Sender<DevtoolsControlMsg>>,
    protocols: ProtocolRegistry,
    user_content_manager: UserContentManager,
)