src/vs/platform/theme/common/styler.ts/attachProgressBarStyler
export function attachProgressBarStyler(widget: IThemable, themeService: IThemeService, style?: IProgressBarStyleOverrides): IDisposable {
	return attachStyler(themeService, {
		progressBarBackground: style?.progressBarBackground || progressBarBackground
	} as IProgressBarStyleOverrides, widget);
}