Implement ES6 rest parameters

test/mjsunit/harmony/rest-params-lazy-parsing.js

+// 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: --harmony-rest-parameters --min-preparse-length=0
+
+function variadic(co, ...values) {
+  var sum = 0;
+  while (values.length) {
+    sum += co * values.pop();
+  }
+  return sum;
+}
+
+assertEquals(90, variadic(2, 1, 2, 3, 4, 5, 6, 7, 8, 9));
+assertEquals(74, variadic(2, 1, 2, 3, 4, 5, 6, 7, 9));
+assertEquals(110, variadic(2, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10));