src/vs/base/common/event.ts/EmitterObserver/endUpdate
class EmitterObserver:		endUpdate<T>(_observable: IObservable<T, void>): void {
			if (--this._counter === 0) {
				if (this._hasChanged) {
					this._hasChanged = false;
					this.emitter.fire(this.obs.get());
				}
			}
		}