[runtime] We don't need an actual instance type for JSIteratorResult.

src/heap/objects-visiting.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/objects-visiting.h"
 
 #include "src/heap/mark-compact-inl.h"
 #include "src/heap/objects-visiting-inl.h"
 
 namespace v8 {
@@ skipping 100 matching lines @@
     case JS_ARRAY_TYPE:
     case JS_GLOBAL_PROXY_TYPE:
     case JS_GLOBAL_OBJECT_TYPE:
     case JS_MESSAGE_OBJECT_TYPE:
     case JS_TYPED_ARRAY_TYPE:
     case JS_DATA_VIEW_TYPE:
     case JS_SET_TYPE:
     case JS_MAP_TYPE:
     case JS_SET_ITERATOR_TYPE:
     case JS_MAP_ITERATOR_TYPE:
-    case JS_ITERATOR_RESULT_TYPE:
     case JS_PROMISE_TYPE:
     case JS_BOUND_FUNCTION_TYPE:
       return GetVisitorIdForSize(kVisitJSObject, kVisitJSObjectGeneric,
                                  instance_size, has_unboxed_fields);
 
     case JS_FUNCTION_TYPE:
       return kVisitJSFunction;
 
     case FILLER_TYPE:
       if (instance_size == kPointerSize) return kVisitDataObjectGeneric;
@@ skipping 221 matching lines @@
 };
 
 
 template Object* VisitWeakList<Context>(Heap* heap, Object* list,
                                         WeakObjectRetainer* retainer);
 
 template Object* VisitWeakList<AllocationSite>(Heap* heap, Object* list,
                                                WeakObjectRetainer* retainer);
 }  // namespace internal
 }  // namespace v8