Bug 1735296 - Part 3: Change Zone::RttValueObjectSet to use HeapPtrObject r=sfink

This was a minor optimisation to remove unnecessary barriers but it probably
makes negligable difference.

Differential Revision: https://phabricator.services.mozilla.com/D128259

Author: jonco3

js/src/gc/Zone.h

@@ -271,11 +271,11 @@ class Zone : public js::ZoneAllocator, public js::gc::GraphNodeBase<JS::Zone> {
   // This is used by the GC to trace them all first when compacting, since the
   // TypedObject trace hook may access these objects.
   //
-  // There are no barriers here - the set contains only tenured objects so no
+  // (Although this uses HeapPtrObject, the set contains only tenured objects so no
   // post-barrier is required, and these are weak references so no pre-barrier
-  // is required.
+  // is required.)
   using RttValueObjectSet =
-      js::GCHashSet<JSObject*, js::MovableCellHasher<JSObject*>,
+      js::GCHashSet<js::HeapPtrObject, js::MovableCellHasher<js::HeapPtrObject>,
                     js::SystemAllocPolicy>;
 
   js::ZoneData<JS::WeakCache<RttValueObjectSet>> rttValueObjects_;