[regexp] fix assertion failure when parsing close to stack overflow.

test/mjsunit/regress/regress-crbug-600257.js

Index: test/mjsunit/regress/regress-crbug-600257.js
diff --git a/test/mjsunit/regress/regress-crbug-595657.js b/test/mjsunit/regress/regress-crbug-600257.js
similarity index 72%
copy from test/mjsunit/regress/regress-crbug-595657.js
copy to test/mjsunit/regress/regress-crbug-600257.js
index 653259781be24ec1acf1d5e2aa4f4de2f361d3ec..87bd2e39af387cde81f9c9adb15756f8139a03a3 100644
--- a/test/mjsunit/regress/regress-crbug-595657.js
+++ b/test/mjsunit/regress/regress-crbug-600257.js
@@ -4,12 +4,10 @@
 
 // Flags: --stack-size=100
 
-function test() {
+(function rec() {
   try {
-    test();
-  } catch(e) {
-    /(\2)(a)/.test("");
+    rec();
+  } catch (e) {
+    /{/;
   }
-}
-
-test();
+})();