src/vs/workbench/browser/parts/activitybar/activitybarPart.ts/ActivitybarPart/onDidRegisterExtensions
class ActivitybarPart:	private onDidRegisterExtensions(): void {
		this.hasExtensionsRegistered = true;

		// show/hide/remove composites
		for (const { id } of this.cachedViewContainers) {
			const viewContainer = this.getViewContainer(id);
			if (viewContainer) {
				this.showOrHideViewContainer(viewContainer);
			} else {
				if (this.viewDescriptorService.isViewContainerRemovedPermanently(id)) {
					this.removeComposite(id);
				} else {
					this.hideComposite(id);
				}
			}
		}

		this.saveCachedViewContainers();
	}