Faster moving FixedArray elements around.

test/mjsunit/undeletable-functions.js

Index: test/mjsunit/undeletable-functions.js
diff --git a/test/mjsunit/undeletable-functions.js b/test/mjsunit/undeletable-functions.js
index 86a74263e3c44a7c7ae5c63a694f1653e76844a1..25664caa745a9e2157cd4e2d953731167e6a23e8 100644
--- a/test/mjsunit/undeletable-functions.js
+++ b/test/mjsunit/undeletable-functions.js
@@ -39,6 +39,11 @@ array = [
   "every", "map", "indexOf", "lastIndexOf", "reduce", "reduceRight"];
 CheckJSCSemantics(Array.prototype, array, "Array prototype");
 
+var old_Array_prototype = Array.prototype;
+var new_Array_prototype = {};
+Array.prototype = new_Array_prototype;
+assertEquals(old_Array_prototype, Array.prototype);
+
 array = [
   "toString", "toDateString", "toTimeString", "toLocaleString",
   "toLocaleDateString", "toLocaleTimeString", "valueOf", "getTime",