src/vs/workbench/contrib/contextmenu/browser/contextmenu.contribution.ts/ContextMenuContribution/constructor
class ContextMenuContribution:	constructor(
		@ILayoutService layoutService: ILayoutService,
		@IContextMenuService contextMenuService: IContextMenuService
	) {
		const update = (visible: boolean) => layoutService.container.classList.toggle('context-menu-visible', visible);
		contextMenuService.onDidShowContextMenu(() => update(true), null, this.disposables);
		contextMenuService.onDidHideContextMenu(() => update(false), null, this.disposables);
	}