[array] Add basic js-perf benchmarks for Array.p.copyWithin

This CL adds basic JS benchmarks for Array.p.copyWithin to get some
feedback for the upcoming Torque implementation.

R=jgruber@chromium.org

Bug: v8:7624
Change-Id: Ic193a2b576d5fb7ac9f39db0379cece9144f979f
Reviewed-on: https://chromium-review.googlesource.com/1167289Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Simon Zünd <szuend@google.com>
Cr-Commit-Position: refs/heads/master@{#54984}

test/js-perf-test/Array/copy-within.js

+// Copyright 2018 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.
+(() => {
+
+const kArraySize = 1000;
+const kQuarterSize = kArraySize / 4;
+
+let array = [];
+
+// Copy a quarter of the elements from the middle to the front.
+function CopyWithin() {
+  return new Function(
+    'array.copyWithin(0, kQuarterSize * 2, kQuarterSize * 3);');
+}
+
+createSuite('SmiCopyWithin', 1000, CopyWithin, SmiCopyWithinSetup);
+createSuite('StringCopyWithin', 1000, CopyWithin, StringCopyWithinSetup);
+createSuite('SparseSmiCopyWithin', 1000, CopyWithin, SparseSmiCopyWithinSetup);
+createSuite(
+    'SparseStringCopyWithin', 1000, CopyWithin, SparseStringCopyWithinSetup);
+
+function SmiCopyWithinSetup() {
+  array = [];
+  for (let i = 0; i < kArraySize; ++i) array[i] = i;
+}
+
+function StringCopyWithinSetup() {
+  array = [];
+  for (let i = 0; i < kArraySize; ++i) array[i] = `Item no. ${i}`;
+}
+
+function SparseSmiCopyWithinSetup() {
+  array = [];
+  for (let i = 0; i < kArraySize; i += 10) array[i] = i;
+}
+
+function SparseStringCopyWithinSetup() {
+  array = [];
+  for (let i = 0; i < kArraySize; i += 10) array[i] = `Item no. ${i}`;
+}
+
+})();

test/js-perf-test/Array/run.js

@@ -77,6 +77,7 @@ load('of.js');
 load('join.js');
 load('to-string.js');
 load('slice.js');
+load('copy-within.js');
 
 var success = true;
 

test/js-perf-test/JSTests.json

@@ -756,7 +756,11 @@
         {"name": "Array.slice(500,999)-dict"},
         {"name": "Array.slice(200,700)-dict"},
         {"name": "Array.slice(200,-300)-dict"},
-        {"name": "Array.slice(4,1)-dict"}
+        {"name": "Array.slice(4,1)-dict"},
+        {"name": "SmiCopyWithin"},
+        {"name": "StringCopyWithin"},
+        {"name": "SparseSmiCopyWithin"},
+        {"name": "SparseStringCopyWithin"}
       ]
     },
     {