[promises] PromiseResolveThenableJob: change then to be a JSReceiver

src/runtime/runtime-internal.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/runtime/runtime-utils.h"
 
 #include <memory>
 
 #include "src/arguments.h"
 #include "src/ast/prettyprinter.h"
@@ skipping 540 matching lines @@
     else
       std::fflush(f);
     return isolate->heap()->undefined_value();
   }
 }
 
 RUNTIME_FUNCTION(Runtime_EnqueuePromiseResolveThenableJob) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 6);
   CONVERT_ARG_HANDLE_CHECKED(JSReceiver, resolution, 0);
-  CONVERT_ARG_HANDLE_CHECKED(JSFunction, then, 1);
+  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, then, 1);
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, resolve, 2);
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, reject, 3);
   CONVERT_ARG_HANDLE_CHECKED(Object, before_debug_event, 4);
   CONVERT_ARG_HANDLE_CHECKED(Object, after_debug_event, 5);
   Handle<PromiseContainer> container = isolate->factory()->NewPromiseContainer(
       resolution, then, resolve, reject, before_debug_event, after_debug_event);
   isolate->EnqueueMicrotask(container);
   return isolate->heap()->undefined_value();
 }
 
@@ skipping 32 matching lines @@
 
 RUNTIME_FUNCTION(Runtime_Typeof) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
   return *Object::TypeOf(isolate, object);
 }
 
 }  // namespace internal
 }  // namespace v8