Bug 1600019 - Part 4: Prefer js::Call over JS::Call for engine-internal calls. r=jonco

`js::Call` avoids copying the arguments into a separate `InvokeArgs` struct,
therefore it's generally preferred for calls within SpiderMonkey.

Depends on D55088

Differential Revision: https://phabricator.services.mozilla.com/D55089

--HG--
extra : moz-landing-system : lando

js/src/builtin/FinalizationGroupObject.cpp

@@ -587,19 +587,22 @@ bool FinalizationGroupObject::cleanupQueuedHoldings(
 
   // 4. If callback is undefined, set callback to
   //    finalizationGroup.[[CleanupCallback]].
-  RootedObject callback(cx, callbackArg);
-  if (!callbackArg) {
-    callback = group->cleanupCallback();
+  RootedValue callback(cx);
+  if (callbackArg) {
+    callback.setObject(*callbackArg);
+  } else {
+    JSObject* cleanupCallback = group->cleanupCallback();
+    MOZ_ASSERT(cleanupCallback);
+    callback.setObject(*cleanupCallback);
   }
 
   // 5. Set finalizationGroup.[[IsFinalizationGroupCleanupJobActive]] to true.
   group->setCleanupJobActive(true);
 
   // 6. Let result be Call(callback, undefined, iterator).
+  RootedValue iteratorVal(cx, ObjectValue(*iterator));
   RootedValue rval(cx);
-  JS::AutoValueArray<1> args(cx);
-  args[0].setObject(*iterator);
-  bool ok = JS::Call(cx, UndefinedHandleValue, callback, args, &rval);
+  bool ok = Call(cx, callback, UndefinedHandleValue, iteratorVal, &rval);
 
   // Remove holdings that were iterated over.
   size_t index = iterator->index();