Add unrooted_must_root lint for usages of JS<T> in let/for bindings

components/script/dom/bindings/callback.rs

@@ -139,6 +139,7 @@ pub struct CallSetup {
 
 impl CallSetup {
     /// Performs the setup needed to make a call.
+    #[allow(unrooted_must_root)]
     pub fn new<T: CallbackContainer>(callback: &T, handling: ExceptionHandling) -> CallSetup {
         let global = global_object_for_js_object(callback.callback());
         let global = global.root();