Always lazy compile arrow functions

test/mjsunit/harmony/regress/regress-4395.js

Index: test/mjsunit/harmony/regress/regress-4395.js
diff --git a/test/message/arrow-param-after-rest.js b/test/mjsunit/harmony/regress/regress-4395.js
similarity index 54%
copy from test/message/arrow-param-after-rest.js
copy to test/mjsunit/harmony/regress/regress-4395.js
index 0fade6c31d3cb6c2e82fb7027628fdfae96e1962..3d957137be1bf61b8a4663f634d10097d457024d 100644
--- a/test/message/arrow-param-after-rest.js
+++ b/test/mjsunit/harmony/regress/regress-4395.js
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
-// Flags: --harmony-rest-parameters --harmony-arrow-functions
+// Flags: --harmony-default-parameters
 
-(...x, y) => 10
+assertEquals([42, 42], ((a, b=a=42) => [a, b])(10));
+assertEquals([10, 10], ((a, b=a) => [a, b])(10));