src/vs/base/browser/ui/menu/menu.ts/Menu/initializeStyleSheet
class Menu:	private initializeStyleSheet(container: HTMLElement): void {
		if (isInShadowDOM(container)) {
			this.styleSheet = createStyleSheet(container);
			this.styleSheet.textContent = MENU_WIDGET_CSS;
		} else {
			if (!Menu.globalStyleSheet) {
				Menu.globalStyleSheet = createStyleSheet();
				Menu.globalStyleSheet.textContent = MENU_WIDGET_CSS;
			}

			this.styleSheet = Menu.globalStyleSheet;
		}
	}