[promises] PromiseResolveThenableJob: change then to be a JSReceiver

src/objects-inl.h

 // Copyright 2012 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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 5637 matching lines @@
           kExpectedReceiverTypeOffset)
 
 ACCESSORS(AccessorInfo, getter, Object, kGetterOffset)
 ACCESSORS(AccessorInfo, setter, Object, kSetterOffset)
 ACCESSORS(AccessorInfo, js_getter, Object, kJsGetterOffset)
 ACCESSORS(AccessorInfo, data, Object, kDataOffset)
 
 ACCESSORS(Box, value, Object, kValueOffset)
 
 ACCESSORS(PromiseContainer, thenable, JSReceiver, kThenableOffset)
-ACCESSORS(PromiseContainer, then, JSFunction, kThenOffset)
+ACCESSORS(PromiseContainer, then, JSReceiver, kThenOffset)
 ACCESSORS(PromiseContainer, resolve, JSFunction, kResolveOffset)
 ACCESSORS(PromiseContainer, reject, JSFunction, kRejectOffset)
 ACCESSORS(PromiseContainer, before_debug_event, Object, kBeforeDebugEventOffset)
 ACCESSORS(PromiseContainer, after_debug_event, Object, kAfterDebugEventOffset)
 
 Map* PrototypeInfo::ObjectCreateMap() {
   return Map::cast(WeakCell::cast(object_create_map())->value());
 }
 
 // static
@@ skipping 2654 matching lines @@
 #undef WRITE_INT64_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_OBJECTS_INL_H_