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

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 40fe23b3e0e13f55182feb20201aa7a92e026c36..204c31c06f4ad7c98ba0e64a8bbce6347fbe480c 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -710,7 +710,6 @@ TYPE_CHECKER(JSSet, JS_SET_TYPE)
 TYPE_CHECKER(JSMap, JS_MAP_TYPE)
 TYPE_CHECKER(JSSetIterator, JS_SET_ITERATOR_TYPE)
 TYPE_CHECKER(JSMapIterator, JS_MAP_ITERATOR_TYPE)
-TYPE_CHECKER(JSIteratorResult, JS_ITERATOR_RESULT_TYPE)
 TYPE_CHECKER(JSWeakMap, JS_WEAK_MAP_TYPE)
 TYPE_CHECKER(JSWeakSet, JS_WEAK_SET_TYPE)
 TYPE_CHECKER(JSContextExtensionObject, JS_CONTEXT_EXTENSION_OBJECT_TYPE)
@@ -2112,8 +2111,6 @@ int JSObject::GetHeaderSize(InstanceType type) {
       return JSSetIterator::kSize;
     case JS_MAP_ITERATOR_TYPE:
       return JSMapIterator::kSize;
-    case JS_ITERATOR_RESULT_TYPE:
-      return JSIteratorResult::kSize;
     case JS_WEAK_MAP_TYPE:
       return JSWeakMap::kSize;
     case JS_WEAK_SET_TYPE:
@@ -3216,7 +3213,6 @@ CAST_ACCESSOR(JSReceiver)
 CAST_ACCESSOR(JSRegExp)
 CAST_ACCESSOR(JSSet)
 CAST_ACCESSOR(JSSetIterator)
-CAST_ACCESSOR(JSIteratorResult)
 CAST_ACCESSOR(JSTypedArray)
 CAST_ACCESSOR(JSValue)
 CAST_ACCESSOR(JSWeakMap)
@@ -7738,10 +7734,6 @@ Object* JSMapIterator::CurrentValue() {
 }
 
 
-ACCESSORS(JSIteratorResult, done, Object, kDoneOffset)
-ACCESSORS(JSIteratorResult, value, Object, kValueOffset)
-
-
 String::SubStringRange::SubStringRange(String* string, int first, int length)
     : string_(string),
       first_(first),