Make ValidateAndApplyPropertyDescriptor pass on its ShouldThrow mode.

This fixes a bug affecting module namespace objects, which are currently
implemented using native accessors.

Bug: v8:6681, v8:1569
Change-Id: I6a678652573a332c47315497d927c390d9da0926
Reviewed-on: https://chromium-review.googlesource.com/606027
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47238}

src/objects.cc

@@ -6918,9 +6918,8 @@ Maybe<bool> JSReceiver::ValidateAndApplyPropertyDescriptor(
                                   ? current->value()
                                   : Handle<Object>::cast(
                                         isolate->factory()->undefined_value()));
-      MaybeHandle<Object> result =
-          JSObject::DefineOwnPropertyIgnoreAttributes(it, value, attrs);
-      if (result.is_null()) return Nothing<bool>();
+      return JSObject::DefineOwnPropertyIgnoreAttributes(it, value, attrs,
+                                                         should_throw);
     } else {
       DCHECK(desc_is_accessor_descriptor ||
              (desc_is_generic_descriptor &&

test/mjsunit/regress/regress-6681.js

+// Copyright 2017 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.
+//
+// MODULE
+
+import * as ns from "./regress-6681.js";
+export var foo;
+
+assertEquals(false, Reflect.defineProperty(ns, 'foo', {value: 123}));