add tiny util to allow performance mark collection (via perf_hooks) independent of amd or commonjs usage

src/vs/base/node/startupPerf.d.ts

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+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { PerformanceEntry } from 'perf_hooks';
+
+/**
+ * Return all performance entries captured so far and stop startup
+ * performance recording.
+ */
+export function consumeAndStop(): PerformanceEntry[];

src/vs/base/node/startupPerf.js

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+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+'use strict';
+
+//@ts-check
+
+function _factory(sharedObj, nodeRequire) {
+	if (!sharedObj.MonacoStartupPerformanceMarks) {
+
+		const { PerformanceObserver } = nodeRequire('perf_hooks');
+
+		let startupEntries = [];
+
+		const startupObs = new PerformanceObserver(list => { startupEntries = startupEntries.concat(list.getEntries()); });
+		startupObs.observe({ buffered: true, entryTypes: ['mark'] });
+
+		sharedObj.MonacoStartupPerformanceMarks = {
+			startupEntries,
+			dispose() {
+				startupObs.disconnect();
+				startupEntries.length = 0;
+				delete sharedObj.MonacoStartupPerformanceMarks;
+			},
+		};
+	}
+
+	return {
+		consumeAndStop() {
+			const entries = sharedObj.startupEntries.slice(0);
+			sharedObj.MonacoStartupPerformanceMarks.dispose();
+			return entries;
+		}
+	};
+}
+
+// This module can be loaded in an amd and commonjs-context.
+// Because we want both instances to use the same perf-data
+// we store them globally
+if (typeof define === 'function') {
+	// amd
+	define([], function () { return _factory(global, require.__$__nodeRequire); });
+} else if (typeof module === 'object' && typeof module.exports === 'object') {
+	// commonjs
+	module.exports = _factory(global, require);
+}