Add test case for 85b8c2dc (fix observable array access in messages.js).

test/mjsunit/regress/regress-crbug-617527.js

Index: test/mjsunit/regress/regress-crbug-617527.js
diff --git a/test/message/generators-throw1.js b/test/mjsunit/regress/regress-crbug-617527.js
similarity index 54%
copy from test/message/generators-throw1.js
copy to test/mjsunit/regress/regress-crbug-617527.js
index f544d33328508d36e9332295807a371c8c303599..cf4662871c4ce68e3e72bd9efa14d1f0258dd987 100644
--- a/test/message/generators-throw1.js
+++ b/test/mjsunit/regress/regress-crbug-617527.js
@@ -1,9 +1,8 @@
 // Copyright 2016 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: --ignition-generators
 
-function* f() { yield }
+// Flags: --enable-slow-asserts
 
-f().throw(42);
+Object.defineProperty(Array.prototype, "1", { get: toLocaleString });
+assertThrows(_ => new RegExp(0, 0));