src/vs/workbench/browser/parts/activitybar/activitybarPart.ts/ActivitybarPart/onDidDeregisterViewContainer
class ActivitybarPart:	private onDidDeregisterViewContainer(viewContainer: ViewContainer): void {
		const disposable = this.viewContainerDisposables.get(viewContainer.id);
		disposable?.dispose();

		this.viewContainerDisposables.delete(viewContainer.id);
		this.removeComposite(viewContainer.id);
	}