Small changes for clarity.

Author: aardvark179

src/main/java/org/truffleruby/cext/CExtNodes.java

@@ -1333,7 +1333,7 @@ protected UnwrapNode createUnwrapNode() {
         }
     }
 
-    private static ThreadLocal<ArrayList<Object>> markList = new ThreadLocal<>();
+    private static final ThreadLocal<ArrayList<Object>> markList = new ThreadLocal<>();
 
     @CoreMethod(names = "create_mark_list", onSingleton = true, required = 0)
     public abstract static class NewMarkerList extends CoreMethodArrayArgumentsNode {

src/main/java/org/truffleruby/language/objects/ObjectGraph.java

@@ -131,6 +131,7 @@ public static Set<DynamicObject> getAdjacentObjects(DynamicObject object) {
                 }
             } else if (propertyValue instanceof Object[]) {
                 for (Object element : (Object[]) propertyValue) {
+                    // Needed to get wrappers set by Truffle::Cext.set_mark_list_on_object.
                     if (element instanceof ValueWrapper) {
                         element = ((ValueWrapper) element).getObject();
                     }