src/vs/base/common/observableImpl/utils.ts/ObservableSignal/trigger
class ObservableSignal:	public trigger(tx: ITransaction | undefined): void {
		if (!tx) {
			transaction(tx => {
				this.trigger(tx);
			}, () => `Trigger signal ${this.debugName}`);
			return;
		}

		for (const o of this.observers) {
			tx.updateObserver(o, this);
			o.handleChange(this, undefined);
		}
	}