Fix JSObject::EnsureCanContainElements to correctly iterate over Arguments

test/mjsunit/elements-kind.js

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 287 matching lines @@
   assertKind(elements_kind.fast, e);
   assertFalse(%HaveSameMap(e, f));
   f[0] = 1.5;
   assertKind(elements_kind.fast_double, f);
   assertFalse(%HaveSameMap(e, f));
   f[0] = "bar";
   assertKind(elements_kind.fast, f);
   assertTrue(%HaveSameMap(e, f));
 }
 
+// Test that Array.push() correctly handles SMI elements.
+if (support_smi_only_arrays) {
+  var a = [1, 2];
+  assertKind(elements_kind.fast_smi_only, a);
+  a.push(3, 4, 5);
+  assertKind(elements_kind.fast_smi_only, a);
+  assertEquals([1, 2, 3, 4, 5], a);
+}
+
 // Throw away type information in the ICs for next stress run.
 gc();