src/vs/workbench/api/browser/viewsExtensionPoint.ts/ViewsExtensionHandler/removeCustomViewContainers
class ViewsExtensionHandler:	private removeCustomViewContainers(extensionPoints: readonly IExtensionPointUser<ViewContainerExtensionPointType>[]): void {
		const viewContainersRegistry = Registry.as<IViewContainersRegistry>(ViewContainerExtensions.ViewContainersRegistry);
		const removedExtensions: Set<string> = extensionPoints.reduce((result, e) => { result.add(ExtensionIdentifier.toKey(e.description.identifier)); return result; }, new Set<string>());
		for (const viewContainer of viewContainersRegistry.all) {
			if (viewContainer.extensionId && removedExtensions.has(ExtensionIdentifier.toKey(viewContainer.extensionId))) {
				// move all views in this container into default view container
				const views = this.viewsRegistry.getViews(viewContainer);
				if (views.length) {
					this.viewsRegistry.moveViews(views, this.getDefaultViewContainer());
				}
				this.deregisterCustomViewContainer(viewContainer);
			}
		}
	}