Provide accessor for object internal properties that doesn't require debugger to be active

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 9a5353fe630eaba44fecc4d3ce558c1babd343d5..ba7eebb6a71c202531e155080e67bc7fbd6257d4 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -112,6 +112,20 @@ bool Object::IsCallable() const {
 }
 
 
+bool Object::IsPromise(Handle<Object> object) {
+  if (!object->IsJSObject()) return false;
+  auto js_object = Handle<JSObject>::cast(object);
+  // Promises can't have access checks.
+  if (js_object->map()->is_access_check_needed()) return false;
+  auto isolate = js_object->GetIsolate();
+  // TODO(dcarney): this should just be read from the symbol registry so as not
+  // to be context dependent.
+  auto key = isolate->promise_status();
+  // Shouldn't be possible to throw here.
+  return JSObject::HasRealNamedProperty(js_object, key).FromJust();
+}
+
+
 MaybeHandle<Object> Object::GetProperty(LookupIterator* it) {
   for (; it->IsFound(); it->Next()) {
     switch (it->state()) {