src/vs/base/browser/ui/menu/menubar.ts/MenuBar/onMenuTriggered
class MenuBar:	private onMenuTriggered(menuIndex: number, clicked: boolean) {
		if (this.isOpen) {
			if (this.isCurrentMenu(menuIndex)) {
				this.setUnfocusedState();
			} else {
				this.cleanupCustomMenu();
				this.showCustomMenu(menuIndex, this.openedViaKeyboard);
			}
		} else {
			this.focusedMenu = { index: menuIndex };
			this.openedViaKeyboard = !clicked;
			this.focusState = MenubarState.OPEN;
		}
	}