Add a Reflectable bound to Trusted's type parameter.

components/script/dom/bindings/refcounted.rs

@@ -47,7 +47,7 @@ unsafe impl Send for TrustedReference {}
 /// shared among tasks for use in asynchronous operations. The underlying
 /// DOM object is guaranteed to live at least as long as the last outstanding
 /// `Trusted<T>` instance.
-pub struct Trusted<T> {
+pub struct Trusted<T: Reflectable> {
     /// A pointer to the Rust DOM object of type T, but void to allow
     /// sending `Trusted<T>` between tasks, regardless of T's sendability.
     ptr: *const libc::c_void,