src/vs/workbench/browser/parts/activitybar/activitybarPart.ts/ActivitybarPart/updateGlobalActivity
class ActivitybarPart:	private updateGlobalActivity(activityId: string): void {
		const activityAction = activityId === GLOBAL_ACTIVITY_ID ? this.globalActivityAction : this.accountsActivityAction;
		if (!activityAction) {
			return;
		}

		const activityCache = activityId === GLOBAL_ACTIVITY_ID ? this.globalActivity : this.accountsActivity;
		if (activityCache.length) {
			const [{ badge, clazz, priority }] = activityCache;
			if (badge instanceof NumberBadge && activityCache.length > 1) {
				const cumulativeNumberBadge = this.getCumulativeNumberBadge(activityCache, priority);
				activityAction.setBadge(cumulativeNumberBadge);
			} else {
				activityAction.setBadge(badge, clazz);
			}
		} else {
			activityAction.setBadge(undefined);
		}
	}