lib: add toJSON to PerformanceMeasure

lib/internal/perf/usertiming.js

@@ -136,6 +136,16 @@ class PerformanceMeasure extends PerformanceEntry {
     validateInternalField(this, kDetail, 'PerformanceMeasure');
     return this[kDetail];
   }
+
+  toJSON() {
+    return {
+      name: this.name,
+      entryType: this.entryType,
+      startTime: this.startTime,
+      duration: this.duration,
+      detail: this[kDetail],
+    };
+  }
 }
 ObjectDefineProperties(PerformanceMeasure.prototype, {
   detail: kEnumerableProperty,

test/parallel/test-performance-measure-detail.js

@@ -0,0 +1,20 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const util = require('util');
+const { performance, PerformanceObserver } = require('perf_hooks');
+
+const perfObserver = new PerformanceObserver(common.mustCall((items) => {
+  const entries = items.getEntries();
+  assert.ok(entries.length === 1);
+  for (const entry of entries) {
+    assert.ok(util.inspect(entry).includes('this is detail'));
+  }
+}));
+
+perfObserver.observe({ entryTypes: ['measure'] });
+
+performance.measure('sample', {
+  detail: 'this is detail',
+});