Add micro-benchmark for toString(16)

Bug: v8:10477
Change-Id: I0ce6cd46d3886a37e96bdd62df263addc5b9631f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2327186Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69136}

test/js-perf-test/JSTests5.json

@@ -551,15 +551,17 @@
       "main": "run.js",
       "flags": ["--allow-natives-syntax"],
       "resources": [
-	      "toNumber.js",
-	      "toLocaleString.js"
+        "toNumber.js",
+        "toLocaleString.js",
+        "toHexString.js"
       ],
       "results_regexp": "^%s\\-Numbers\\(Score\\): (.+)$",
       "tests": [
         {"name": "Constructor"},
         {"name": "UnaryPlus"},
         {"name": "ParseFloat"},
-        {"name": "toLocaleString"}
+        {"name": "toLocaleString"},
+        {"name": "toHexString"}
       ]
     },
     {

test/js-perf-test/Numbers/run.js

@@ -4,6 +4,7 @@
 load('../base.js');
 load('toNumber.js');
 load('toLocaleString.js');
+load('toHexString.js');
 
 function PrintResult(name, result) {
   console.log(name);

test/js-perf-test/Numbers/toHexString.js

+// Copyright 2020 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.
+
+function NumberToHexString() {
+  Number(0).toString(16);
+  Number(-12).toString(16);
+  Number(13).toString(16);
+  Number(123456789).toString(16);
+  Number(1234567.89).toString(16);
+  Number(-123456789).toString(16);
+  Number(-1234567.89).toString(16);
+}
+createSuite('toHexString', 100000, NumberToHexString, ()=>{});