src/vs/workbench/services/views/browser/viewDescriptorService.ts/ViewDescriptorService/onDidChangeVisibleViews
class ViewDescriptorService:	private onDidChangeVisibleViews({ added, removed }: { added: IViewDescriptor[]; removed: IViewDescriptor[] }): void {
		this.contextKeyService.bufferChangeEvents(() => {
			added.forEach(viewDescriptor => this.getOrCreateVisibleViewContextKey(viewDescriptor).set(true));
			removed.forEach(viewDescriptor => this.getOrCreateVisibleViewContextKey(viewDescriptor).set(false));
		});
	}