[promises] Move PromiseResolveThenableJob to c++

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index c7b7486d1e6be0e650d1357e7ca9357efc445745..fb5d9a74582cbd49d4147a06cb4d1381881aa39f 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2914,9 +2914,46 @@ void Isolate::ReportPromiseReject(Handle<JSObject> promise,
       v8::Utils::StackTraceToLocal(stack_trace)));
 }
 
+void Isolate::PromiseResolveThenableJob(Handle<PromiseContainer> container) {
+  Handle<JSFunction> then(container->then(), this);
+  SaveContext save(this);
+  set_context(then->context()->native_context());
+  handle_scope_implementer_->EnterMicrotaskContext(
+      handle(then->context(), this));
+
+  Handle<Object> before_debug_event(container->before_debug_event(), this);
+  if (debug()->is_active() && before_debug_event->IsJSObject()) {
+    debug()->OnAsyncTaskEvent(Handle<JSObject>::cast(before_debug_event));
+  }
+
+  MaybeHandle<Object> maybe_exception;
+  Handle<JSObject> promise(container->promise(), this);

[adamk, 2016/09/14 22:52:51]

This doesn't seem to be used at all. Why is it passed in?

+  Handle<JSObject> thenable(container->thenable(), this);
+  Handle<JSFunction> resolve(container->resolve(), this);
+  Handle<JSFunction> reject(container->reject(), this);
+  Handle<Object> argv[] = {resolve, reject};
+  MaybeHandle<Object> result = Execution::TryCall(
+      this, then, thenable, arraysize(argv), argv, &maybe_exception);
+
+  Handle<Object> reason;
+  if (maybe_exception.ToHandle(&reason)) {
+    Handle<Object> reason_arg[] = {reason};
+    MaybeHandle<Object> status =
+        Execution::Call(this, reject, factory()->undefined_value(),

[adamk, 2016/09/14 22:52:51]

What happens if the reject handler throws?

+                        arraysize(reason_arg), reason_arg);
+  }
+
+  Handle<Object> after_debug_event(container->after_debug_event(), this);
+  if (debug()->is_active() && after_debug_event->IsJSObject()) {
+    debug()->OnAsyncTaskEvent(Handle<JSObject>::cast(after_debug_event));
+  }
+
+  handle_scope_implementer_->LeaveMicrotaskContext();
+}
 
 void Isolate::EnqueueMicrotask(Handle<Object> microtask) {
-  DCHECK(microtask->IsJSFunction() || microtask->IsCallHandlerInfo());
+  DCHECK(microtask->IsJSFunction() || microtask->IsCallHandlerInfo() ||
+         microtask->IsPromiseContainer());
   Handle<FixedArray> queue(heap()->microtask_queue(), this);
   int num_tasks = pending_microtask_count();
   DCHECK(num_tasks <= queue->length());
@@ -2977,13 +3014,15 @@ void Isolate::RunMicrotasksInternal() {
           set_pending_microtask_count(0);
           return;
         }
-      } else {
+      } else 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 {
+        PromiseResolveThenableJob(Handle<PromiseContainer>::cast(microtask));
       }
     });
   }