src/vs/workbench/api/common/extHostTextEditor.ts/ExtHostTextEditorOptions/_validateTabSize
class ExtHostTextEditorOptions:	private _validateTabSize(value: number | string): number | 'auto' | null {
		if (value === 'auto') {
			return 'auto';
		}
		if (typeof value === 'number') {
			const r = Math.floor(value);
			return (r > 0 ? r : null);
		}
		if (typeof value === 'string') {
			const r = parseInt(value, 10);
			if (isNaN(r)) {
				return null;
			}
			return (r > 0 ? r : null);
		}
		return null;
	}