Fix Reflect.construct with constructors without a prototype slot

Bug: chromium:907714
Change-Id: Ie8eacff1b12ec74faa392a1d2c8545f873ab13a1
Reviewed-on: https://chromium-review.googlesource.com/c/1351023Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57866}

src/objects.cc

@@ -13383,6 +13383,8 @@ namespace {
 bool FastInitializeDerivedMap(Isolate* isolate, Handle<JSFunction> new_target,
                               Handle<JSFunction> constructor,
                               Handle<Map> constructor_initial_map) {
+  // Use the default intrinsic prototype instead.
+  if (!new_target->has_prototype_slot()) return false;
   // Check that |function|'s initial map still in sync with the |constructor|,
   // otherwise we must create a new initial map for |function|.
   if (new_target->has_initial_map() &&
@@ -13457,9 +13459,14 @@ MaybeHandle<Map> JSFunction::GetDerivedMap(Isolate* isolate,
   Handle<Object> prototype;
   if (new_target->IsJSFunction()) {
     Handle<JSFunction> function = Handle<JSFunction>::cast(new_target);
+    if (function->has_prototype_slot()) {
       // Make sure the new.target.prototype is cached.
       EnsureHasInitialMap(function);
       prototype = handle(function->prototype(), isolate);
+    } else {
+      // No prototype property, use the intrinsict default proto further down.
+      prototype = isolate->factory()->undefined_value();
+    }
   } else {
     Handle<String> prototype_string = isolate->factory()->prototype_string();
     ASSIGN_RETURN_ON_EXCEPTION(

test/mjsunit/regress/regress-crbug-90771.js

+// Copyright 2018 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.
+
+
+// Flags: --allow-natives-syntax
+function target() {};
+
+for (let key of Object.getOwnPropertyNames(this)) {
+  try {
+    let newTarget = this[key];
+    let arg = target;
+    Reflect.construct(target, arg, newTarget);
+  } catch {}
+}