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

src/bootstrapper.cc

 // Copyright 2014 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/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/code-stubs.h"
 #include "src/extensions/externalize-string-extension.h"
@@ skipping 1557 matching lines @@
   {  // -- S e t
     Handle<JSFunction> js_set_fun = InstallFunction(
         global, "Set", JS_SET_TYPE, JSSet::kSize,
         isolate->initial_object_prototype(), Builtins::kIllegal);
     InstallWithIntrinsicDefaultProto(isolate, js_set_fun,
                                      Context::JS_SET_FUN_INDEX);
   }
 
   {  // -- I t e r a t o r R e s u l t
     Handle<Map> map =
-        factory->NewMap(JS_ITERATOR_RESULT_TYPE, JSIteratorResult::kSize);
+        factory->NewMap(JS_OBJECT_TYPE, JSIteratorResult::kSize);
     Map::SetPrototype(map, isolate->initial_object_prototype());
     Map::EnsureDescriptorSlack(map, 2);
 
     {  // value
       DataDescriptor d(factory->value_string(), JSIteratorResult::kValueIndex,
                        NONE, Representation::Tagged());
       map->AppendDescriptor(&d);
     }
 
     {  // done
@@ skipping 2043 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8