Simplify event loop start-up

Move the layout constraint tracker into the window where we can apply
the constraints right before drawing, instead of doing that from within
the event loop. This allows to remove the component parameter from the
run function.

api/sixtyfps-node/native/lib.rs

@@ -329,7 +329,7 @@ declare_types! {
             let component = cx.borrow(&mut this, |x| x.0.clone());
             let component = component.ok_or(()).or_else(|()| cx.throw_error("Invalid type"))?;
             run_scoped(&mut cx,this.downcast().unwrap(), || {
-                component.window().run(&vtable::VRc::into_dyn(component));
+                component.window().run();
                 Ok(())
             })?;
             Ok(JsUndefined::new().as_value(&mut cx))