src/vs/platform/telemetry/browser/1dsAppender.ts/OneDataSystemWebAppender/constructor
class OneDataSystemWebAppender:	constructor(
		eventPrefix: string,
		defaultData: { [key: string]: any } | null,
		iKeyOrClientFactory: string | (() => AppInsightsCore), // allow factory function for testing
	) {
		super(eventPrefix, defaultData, iKeyOrClientFactory);

		// If we cannot fetch the endpoint it means it is down and we should not send any telemetry.
		// This is most likely due to ad blockers
		fetch(this.endPointUrl, { method: 'POST' }).catch(err => {
			this._aiCoreOrKey = undefined;
		});
	}