Change global const handling to silently ignore redeclarations

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 04fd06068d0b7b7616070b143ec4aa4b9c015a36..bbb798f3516e7f2a96f85540e9443271246e65ed 100644
--- a/test/mjsunit/undeletable-functions.js
+++ b/test/mjsunit/undeletable-functions.js
@@ -76,6 +76,8 @@ array = [
   "execScript"];
 CheckEcmaSemantics(this, array, "Global");
 CheckReadOnlyAttr(this, "Infinity");
+CheckReadOnlyAttr(this, "NaN");
+CheckReadOnlyAttr(this, "undefined");
 
 array = ["exec", "test", "toString", "compile"];
 CheckEcmaSemantics(RegExp.prototype, array, "RegExp prototype");
@@ -189,7 +191,7 @@ function CheckReadOnlyAttr(type, prop) {
   assertFalse(deleted, "delete operator returned true: " + prop);
   assertTrue(type.hasOwnProperty(prop), "not there after delete: " + prop);
   type[prop] = "foo";
-  assertEquals("foo", type[prop], "overwritable: " + prop);
+  assertEquals(old, type[prop], "overwritable: " + prop);
 }
 
 print("OK");