src/vs/workbench/browser/parts/activitybar/activitybarPart.ts/ActivitybarPart/onDidChangeViewContainers
class ActivitybarPart:	private onDidChangeViewContainers(added: readonly { container: ViewContainer; location: ViewContainerLocation }[], removed: readonly { container: ViewContainer; location: ViewContainerLocation }[]) {
		removed.filter(({ location }) => location === ViewContainerLocation.Sidebar).forEach(({ container }) => this.onDidDeregisterViewContainer(container));
		this.onDidRegisterViewContainers(added.filter(({ location }) => location === ViewContainerLocation.Sidebar).map(({ container }) => container));
	}