Convert to immutable heap number when materializing arguments object.

test/mjsunit/regress/regress-457935.js

Index: test/mjsunit/regress/regress-457935.js
diff --git a/test/mjsunit/array-push12.js b/test/mjsunit/regress/regress-457935.js
similarity index 57%
copy from test/mjsunit/array-push12.js
copy to test/mjsunit/regress/regress-457935.js
index f4c15b484b41197c9007113ecf8f91fe909cc5d3..d34db05de439a20b54f81b45eb7fdbcf35ac48b4 100644
--- a/test/mjsunit/array-push12.js
+++ b/test/mjsunit/regress/regress-457935.js
@@ -4,20 +4,23 @@
 
 // Flags: --allow-natives-syntax
 
-var a = [];
-for (var i = -20; i < 0; ++i) {
-  a[i] = 0;
-}
+function dummy(x) { };
 
 function g() {
-    [].push.apply(a, arguments);
+  return g.arguments;
 }
 
-function f() {
-  g();
+function f(limit) {
+  var i = 0;
+  var o = {};
+  for (; i < limit; i++) {
+    o.y = +o.y;
+    g();
+  }
 }
 
-g();
-g();
+f(1);
+f(1);
 %OptimizeFunctionOnNextCall(f);
-f();
+dummy(f(1));
+dummy(f(2));