src/vs/platform/theme/browser/defaultStyles.ts/getCheckboxStyles
export function getCheckboxStyles(override: IStyleOverride<ICheckboxStyles>): ICheckboxStyles {
	return {
		checkboxBackground: asCssValue(override.checkboxBackground ?? checkboxBackground),
		checkboxBorder: asCssValue(override.checkboxBorder ?? checkboxBorder),
		checkboxForeground: asCssValue(override.checkboxForeground ?? checkboxForeground)
	};
}