[promises] PromiseResolveThenableJob: change then to be a JSReceiver

src/isolate.cc

 // 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.
 
 #include "src/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 2963 matching lines @@
   if (debug()->is_active()) {
     Handle<Object> before_debug_event(container->before_debug_event(), this);
     if (before_debug_event->IsJSObject()) {
       debug()->OnAsyncTaskEvent(Handle<JSObject>::cast(before_debug_event));
     }
   }
 
   Handle<JSReceiver> thenable(container->thenable(), this);
   Handle<JSFunction> resolve(container->resolve(), this);
   Handle<JSFunction> reject(container->reject(), this);
-  Handle<JSFunction> then(container->then(), this);
+  Handle<JSReceiver> then(container->then(), this);
   Handle<Object> argv[] = {resolve, reject};
   *result = Execution::TryCall(this, then, thenable, arraysize(argv), argv,
                                maybe_exception);
 
   Handle<Object> reason;
   if (maybe_exception->ToHandle(&reason)) {
     DCHECK(result->is_null());
     Handle<Object> reason_arg[] = {reason};
     *result =
         Execution::TryCall(this, reject, factory()->undefined_value(),
@@ skipping 55 matching lines @@
 
       if (microtask->IsCallHandlerInfo()) {
         Handle<CallHandlerInfo> callback_info =
             Handle<CallHandlerInfo>::cast(microtask);
         v8::MicrotaskCallback callback =
             v8::ToCData<v8::MicrotaskCallback>(callback_info->callback());
         void* data = v8::ToCData<void*>(callback_info->data());
         callback(data);
       } else {
         SaveContext save(this);
-        Context* context =
-            microtask->IsJSFunction()
-                ? Handle<JSFunction>::cast(microtask)->context()
-                : Handle<PromiseContainer>::cast(microtask)->then()->context();
+        Context* context = microtask->IsJSFunction()
+                               ? Handle<JSFunction>::cast(microtask)->context()
+                               : Handle<PromiseContainer>::cast(microtask)
+                                     ->resolve()
+                                     ->context();
         set_context(context->native_context());
         handle_scope_implementer_->EnterMicrotaskContext(
             Handle<Context>(context, this));
 
         MaybeHandle<Object> result;
         MaybeHandle<Object> maybe_exception;
 
         if (microtask->IsJSFunction()) {
           Handle<JSFunction> microtask_function =
               Handle<JSFunction>::cast(microtask);
@@ skipping 193 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8