benchmark: add subarray to buffer-slice

PR-URL: nodejs#41596
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

benchmark/buffers/buffer-slice.js

@@ -3,18 +3,22 @@ const common = require('../common.js');
 const SlowBuffer = require('buffer').SlowBuffer;
 
 const bench = common.createBenchmark(main, {
-  type: ['fast', 'slow'],
+  type: ['fast', 'slow', 'subarray'],
   n: [1e6]
 });
 
 const buf = Buffer.allocUnsafe(1024);
 const slowBuf = new SlowBuffer(1024);
 
 function main({ n, type }) {
-  const b = type === 'fast' ? buf : slowBuf;
+  const b = type === 'slow' ? slowBuf : buf;
+  const fn = type === 'subarray' ?
+    () => b.subarray(10, 256) :
+    () => b.slice(10, 256);
+
   bench.start();
   for (let i = 0; i < n; i++) {
-    b.slice(10, 256);
+    fn();
   }
   bench.end(n);
 }