[d8] Make exception reporting more resilient.

test/mjsunit/regress/regress-crbug-620253.js

Index: test/mjsunit/regress/regress-crbug-620253.js
diff --git a/test/mjsunit/regress-604044.js b/test/mjsunit/regress/regress-crbug-620253.js
similarity index 69%
copy from test/mjsunit/regress-604044.js
copy to test/mjsunit/regress/regress-crbug-620253.js
index 58ccfbed99181d1c19df7c169259e9d5e7831547..811a4e77154f650ff1f73bd7d6ff7e6af0e1260d 100644
--- a/test/mjsunit/regress-604044.js
+++ b/test/mjsunit/regress/regress-crbug-620253.js
@@ -2,6 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --min-preparse-length 1
+// Flags: --throws
 
-(function(_ = function() {}){})
+load("test/mjsunit/regress/regress-crbug-620253.js");