Improve Array.shift() performance for small arrays.

test/mjsunit/array-shift3.js

Index: test/mjsunit/array-shift3.js
diff --git a/test/mjsunit/array-shift3.js b/test/mjsunit/array-shift3.js
new file mode 100644
index 0000000000000000000000000000000000000000..3a0afc596b11c28446870636e50143d99b95f2bc
--- /dev/null
+++ b/test/mjsunit/array-shift3.js
@@ -0,0 +1,15 @@
+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+Array.prototype[1] = "element 1";
+function test(a) {
+  a.shift();
+  return a;
+}
+assertEquals(["element 1",{}], test([0,,{}]));
+assertEquals(["element 1",10], test([9,,10]));
+%OptimizeFunctionOnNextCall(test);
+assertEquals(["element 1",10], test([9,,10]));