[Runtime] Set expected_nof_properties when creating Constructors

Bug: chromium:800032
Change-Id: I2ba740a3617df3652475e8fc5bd8e8e33cb14a0d
Reviewed-on: https://chromium-review.googlesource.com/861886
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50526}

src/factory.cc

@@ -1606,6 +1606,7 @@ Handle<JSFunction> Factory::NewFunction(const NewFunctionArgs& args) {
     }
     Handle<Map> initial_map = NewMap(args.type_, args.instance_size_,
                                      elements_kind, args.inobject_properties_);
+    result->shared()->set_expected_nof_properties(args.inobject_properties_);
     // TODO(littledan): Why do we have this is_generator test when
     // NewFunctionPrototype already handles finding an appropriately
     // shared prototype?

test/mjsunit/regress/regress-crbug-800032.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 --expose-gc
+
+
+class Derived extends RegExp {
+  constructor(a) {
+    // Syntax Error
+    const a = 1;
+  }
+}
+
+let o = Reflect.construct(RegExp, [], Derived);
+%HeapObjectVerify(o);
+// Check that we can properly access lastIndex.
+assertEquals(o.lastIndex, 0);
+o.lastIndex = 1;
+assertEquals(o.lastIndex, 1);
+o.lastIndex = 0;
+gc();