src/vs/workbench/services/activity/browser/activityService.ts/ActivityService/showViewActivity
class ActivityService:	showViewActivity(viewId: string, activity: IActivity): IDisposable {
		let maybeItem = this.viewActivities.get(viewId);

		if (maybeItem) {
			maybeItem.id++;
		} else {
			maybeItem = {
				id: 1,
				activity: this.instantiationService.createInstance(ViewContainerActivityByView, viewId)
			};

			this.viewActivities.set(viewId, maybeItem);
		}

		const id = maybeItem.id;
		maybeItem.activity.setActivity(activity);

		const item = maybeItem;
		return toDisposable(() => {
			if (item.id === id) {
				item.activity.dispose();
				this.viewActivities.delete(viewId);
			}
		});
	}