src/vs/base/common/worker/simpleWorker.ts/SimpleWorkerProtocol/_handleEventMessage
class SimpleWorkerProtocol:	private _handleEventMessage(msg: EventMessage): void {
		if (!this._pendingEmitters.has(msg.req)) {
			console.warn('Got event for unknown req');
			return;
		}
		this._pendingEmitters.get(msg.req)!.fire(msg.event);
	}