src/vs/workbench/browser/parts/compositeBar.ts/CompositeBar/showActivity
class CompositeBar:	showActivity(compositeId: string, badge: IBadge, clazz?: string, priority?: number): IDisposable {
		if (!badge) {
			throw illegalArgument('badge');
		}

		if (typeof priority !== 'number') {
			priority = 0;
		}

		const activity: ICompositeActivity = { badge, clazz, priority };
		this.model.addActivity(compositeId, activity);

		return toDisposable(() => this.model.removeActivity(compositeId, activity));
	}