src/vs/base/worker/defaultWorkerFactory.ts/DefaultWorkerFactory/create
class DefaultWorkerFactory:	public create(moduleId: string, onMessageCallback: IWorkerCallback, onErrorCallback: (err: any) => void): IWorker {
		let workerId = (++DefaultWorkerFactory.LAST_WORKER_ID);

		if (this._webWorkerFailedBeforeError) {
			throw this._webWorkerFailedBeforeError;
		}

		return new WebWorker(moduleId, workerId, this._label || 'anonymous' + workerId, onMessageCallback, (err) => {
			logOnceWebWorkerWarning(err);
			this._webWorkerFailedBeforeError = err;
			onErrorCallback(err);
		});
	}