Don't double-check elements in the prototype chain in array builtins

test/mjsunit/array-natives-elements.js

Index: test/mjsunit/array-natives-elements.js
diff --git a/test/mjsunit/array-natives-elements.js b/test/mjsunit/array-natives-elements.js
index e567e7f48086615dcd634704ad58b3ab0842645e..a19a931adbf5ebee90cc50af5b66a37a8fbc85bf 100644
--- a/test/mjsunit/array-natives-elements.js
+++ b/test/mjsunit/array-natives-elements.js
@@ -274,9 +274,7 @@ function array_natives_test() {
   assertEquals([1,1,2,3], a4);
   a4 = [1,2,3];
   a4.unshift(1.1);
-  // TODO(verwaest): We'll want to support double unshifting as well.
-  // assertTrue(%HasFastDoubleElements(a4));
-  assertTrue(%HasFastObjectElements(a4));
+  assertTrue(%HasFastDoubleElements(a4));
   assertEquals([1.1,1,2,3], a4);
   a4 = [1.1,2,3];
   a4.unshift(1);