servo: Merge #15127 - Privatize RootedTraceableSet (from servo:RootedTraceableSet); r=jdm

Source-Repo: https://github.com/servo/servo
Source-Revision: 5cd04259334270daa93743aaa6a72c039082bf5e

servo/components/script/dom/bindings/trace.rs

@@ -581,7 +581,7 @@ unsafe impl JSTraceable for RwLock<MediaList> {
 }
 
 /// Holds a set of JSTraceables that need to be rooted
-pub struct RootedTraceableSet {
+struct RootedTraceableSet {
     set: Vec<*const JSTraceable>,
 }