[Test] Add SixSpeed tests for spread literals.

test/js-perf-test/SixSpeed/spread_literal/babel.js

+// Copyright 2017 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.
+
+// This benchmark is based on the six-speed benchmark build output.
+// Copyright 2014 Kevin Decker <https://github.com/kpdecker/six-speed/>
+
+new BenchmarkSuite('Babel', [1000], [
+  new Benchmark('Babel', false, false, 0, Babel),
+]);
+
+function Babel() {
+  return [1].concat([1, 2, 3]);
+}